Category: Class 12

MP Board Class 12th Biology Solutions Chapter 4 जनन स्वास्थ्य

जनन स्वास्थ्य NCERT प्रश्नोत्तर

प्रश्न 1.
समाज में जनन स्वास्थ्य के महत्व के बारे में अपने विचार प्रकट कीजिए।
उत्तर
जनन स्वास्थ्य का तात्पर्य जनन के सभी पहलुओं जैसे शारीरिक, भावनात्मक, व्यावहारिक तथा सामाजिक स्वास्थ्य से है। दुनिया में भारत पहला ऐसा देश है जिसने राष्ट्रीय स्तर पर जननात्मक स्वस्थ समाज को प्राप्त करने की कार्य योजनाएँ बनाई हैं। इन कार्यक्रमों को परिवार कल्याण के नाम से जाना जाता है। इनकी शुरूआत 1951 में (परिवार नियोजन के नाम से) हुई थी। जनन संबंधित और आवधिक क्षेत्रों को इसमें सम्मिलित करते हुए बहुत उन्नत व व्यापक कार्यक्रम फिलहाल ‘जनन एवं बाल स्वास्थ्य सेवा कार्यक्रम (आ.सी.एच.)’ के नाम से प्रसिद्ध है। इन कार्यक्रमों के अंतर्गत् जनन संबंधी विभिन्न पहलुओं के बारे में लोगों में जागरूकता पैदा करते हुए और जननात्मक रूप से संबंध समाज तैयार करने के लिए अनेक सुविधाएँ एवं प्रोत्साहन दिए जा रहे हैं।

प्रश्न 2.
जनन स्वास्थ्य के उन पहलुओं को समझाइए, जिस पर आज के परिदृश्य में विशेष ध्यान देने की जरूरत है
उत्तर
जनन स्वास्थ्य प्राप्ति के लिए विभिन्न कार्य-योजनाओं के सफलतापूर्वक क्रियान्वयन के लिए मजबूत संरचनात्मक सुविधाओं, व्यावसायिक विशेषज्ञता तथा भरपूर भौतिक सहारों की आवश्यकता होती है। लोगों को जनन संबंधी समस्याओं जैसे-सगर्भता (Pregnancy), प्रसव (Parturition), यौन संचारित रोगों, गर्भपात (Abortion), गर्भ निरोधकों, आर्तव चक्र संबंधी समस्याओं, बांझपन (Infertility) आदि के बारे में चिकित्सकीय सहायता देने के लिए बेहतर तकनीकों एवं नई कार्य योजनाओं को क्रियान्वित करने की भी आवश्यकता है ताकि लोगों की अधिक सुचारु रूप से देखभाल और सहायता की जा सके।

बढ़ती “मादा भ्रूण हत्या” की कानूनी रोक के लिए ऐम्नियोसेंटेसिस (Amniocentesis) जैसे लिंग परीक्षण पर वैधानिक प्रतिबंध तथा व्यापक बाल प्रतिरक्षीकरण (टीकाकरण) आदि कुछ महत्वपूर्ण कार्यक्रमों को शामिल किया गया है। जनन संबंधी विभिन्न अनुसंधानों को बढ़ावा देने के लिए हमारे देश की सरकारी एजेंसियाँ सतत् क्रियाशील हैं। लखनऊ स्थित केन्द्रीय औषध अनुसंधान संस्थान (Central Drug Research Institue CDRI) ने “सहेली” नामक गर्भनिरोधक गोली का निर्माण किया है। यौन संचारित रोगों की सही जाँच तथा देखभाल और लगभग सभी जनन स्वास्थ्य समस्याओं हेतु विकसित चिकित्सा सुविधाओं के होने से बेहतर समाज एवं जनन स्वास्थ्य के संकेत प्राप्त हो रहे हैं।

प्रश्न 3.
क्या विद्यालयों में यौन शिक्षा आवश्यक है ? यदि हाँ तो क्यों ?
उत्तर
हाँ, विद्यालयों में यौन शिक्षा आवश्यक है, ताकि छात्र/छात्राओं को यौन संबंधी विभिन्न पहलुओं के बारे में फैली हुई भ्रान्तियों एवं यौन संबंधी गलत धारणाओं से छुटकारा मिल सके। बच्चों को जनन अंगों, किशोरावस्था एवं उससे संबंधित परिवर्तनों, सुरक्षित और स्वच्छ यौन क्रियाओं, यौन संचारित रोगों एवं एड्स की जानकारी देना विशेष रूप से किशोर आयु वर्ग में जनन संबंधी स्वस्थ जीवन बिताने में सहायक होती है।

प्रश्न 4.
क्या आप मानते हैं कि पिछले 50 वर्षों के दौरान हमारे देश के जनन स्वास्थ्य में सुधार हुआ है? यदि हाँ तो इस प्रकार के सुधार वाले कुछ क्षेत्रों का वर्णन कीजिए।
उत्तर
जी हाँ, पिछले 50 वर्षों के दौरान हमारे देश के जनन स्वास्थ्य क्षेत्र में सुधार हुआ है। निम्न क्षेत्रों में हुए सुधार को आसानी से देखा जा सकता है

1. यौन संबंधी मामलों के बारे में बेहतर जागरुकता आयी है।
2. चिकित्सकीय देख-रेख में होने वाले प्रसवों की संख्या में वृद्धि हुई है।
3. प्रसवोत्तर देखभाल बेहतर हुई है।
4. मातृ मृत्यु-दर (MMR) में गिरावट आई है।
5. शिशु मृत्यु-दर (IMR) में गिरावट आई है।
6. यौन संचारित रोगों की सही जाँच-पड़ताल तथा देखभाल व उपचार बेहतर हुआ है।
7. जनसंख्या वृद्धि दर पर रोक लगी है।
   कुल मिलाकर सभी यौन समस्याओं हेतु बढ़ी हुई चिकित्सा सुविधाओं का होना समाज के बेहतर जनन स्वास्थ्य की ओर संकेत देता है।

प्रश्न 5.
जनसंख्या विस्फोट के कौन-से कारण हैं ?
उत्तर
शीघ्र एवं अनियमित जनसंख्या वृद्धि को जनसंख्या विस्फोट कहा जाता है।इसके प्रमुख कारण निम्नलिखित हैं

1. रोगों व महामारियों पर नियंत्रण
2. कृषि का विकास
3. संचार व आवागमन के साधन
4. उच्च जन्मदर
5. निम्न मृत्युदर
6. मनुष्य का वर्ष भर मैथुनकाल होना।

प्रश्न 6.
क्या गर्भ-निरोधकों का उपयोग न्यायोचित है ? कारण बताइए।
उत्तर
भारत में जनसंख्या वृद्धि-दर अत्यधिक होने के कारण राष्ट्रीय संकट उत्पन्न हो गया है। अतः गर्भ निरोधकों का उपयोग न्यायोचित है। इसके उपयोग से परिवार को सीमित किया जा सकता है एवं उनकी सुविधाओं में वृद्धि की जा सकती है। इन गर्भ निरोधकों के उपयोग से यौन संचारित रोगों (STDs) से बचा जा सकता है। इसके साथ ही दो संतानों के बीच अन्तराल भी रखा जा सकता है।जनसंख्या वृद्धि को कम करके परिवार, समाज व देश की समृद्धि में सहयोग कर सकते हैं।

प्रश्न 7.
जनन ग्रंथि को हटाना, गर्भ निरोधकों का विकल्प नहीं माना जा सकता है, क्यों?
उत्तर
जनन ग्रंथियाँ सन्तान उत्पन्न करने वाले अंग हैं । वृषण में शुक्राणुओं तथा अण्डाशय में अण्डों का निर्माण होता है। गर्भ निरोधक के लिए स्वस्थ अंगों को शरीर से हटाना उचित नहीं है। इससे मानसिक, शारीरिक स्वास्थ्य संबंधी समस्याएँ उत्पन्न हो सकती हैं। जबकि गर्भ निरोधक विधियाँ सुलभ होती हैं एवं उनका कोई बुरा प्रभाव भी शरीर पर नहीं पड़ता है। इनका आसानी से प्रयोग भी किया जा सकता है। जरूरत पड़ने पर इसे हटाया भी जा सकता है। जनन ग्रंथि को हटाना एक जटिल प्रक्रिया है, कानून हमें इसकी आज्ञा भी नहीं देता है।

प्रश्न 8.
उल्बवेधन एक घातक लिंग निर्धारण (जाँच) प्रक्रिया है, जो हमारे देश में निषेधित है। क्या यह आवश्यक होना चाहिए ? टिप्पणी कीजिए।
उत्तर
बढ़ती मादा भ्रूण हत्या की कानूनी रोक के लिए उल्बवेधन (Amniocentesis) जाँच (भ्रूणीय लिंग निर्धारण), लिंग परीक्षण पर वैधानिक प्रतिबंध उचित है क्योंकि यह एक खतरनाक प्रवृत्ति है। कई बार ऐसा देखा जाता है कि यह पता चलने पर कि भ्रूण मादा (लड़की) है, चिकित्सीय सगर्भता समापन (Medical termination of pregnancy) कराया जाता है, सामान्य भाषा में इसे गर्भपात (Abortion) कहा जाता है। यह पूरी तरह गैर-कानूनी है। इस प्रकार की प्रवृत्ति से बचना चाहिए क्योंकि यह माता एवं बच्चा (भ्रूण) दोनों के लिए खतरनाक है । इससे समाज में पुरुष एवं महिलाओं की संख्या का अनुपात भी बिगड़ सकता है। जिससे वैवाहिक तथा स्वास्थ्य संबंधी समस्याएँ भी उत्पन्न हो सकती हैं।

प्रश्न 9.
बन्ध्य दम्पत्तियों को संतान पाने हेतु सहायता देने वाली कुछ विधियाँ बताइए।
उत्तर
यदि दंपत्ति बच्चा पैदा करने में अक्षम है तथा ऐसे दोष को ठीक करने का इलाज संभव न हो तो कुछ विशेष तकनीकों के द्वारा उन्हें बच्चा पैदा करने में सहायता की जा सकती है, ये तकनीकें सहायक जनन प्रौद्योगिकी (ART) कहलाती हैं।
1. पात्रे निषेचन (Invitro fertilization IVF)-
इस विधि में अण्डाणु का निषेचन शरीर से बाहर लगभग शरीर के भीतर जैसी स्थिति में कराया जाता है। इसके पश्चात् स्त्री में भ्रूण स्थानान्तरण (Embryo transfer, ET) कराया जाता है।

• युग्मनज डिंबवाहिनी स्थानान्तरण (Zygote intrafallopian transfer ZIFT)-इस प्रक्रिया में प्रारंभिक भ्रूण को 8 ब्लास्टोमियर तक की अवस्था में स्त्री की डिंबवाहिनी या फैलोपियन नलिका में अग्रिम परिवर्धन के लिए स्थानांतरित किया जाता है।
• आन्तर गर्भाशयी स्थानान्तरण (Intrauterine transfer IUT)-जब भ्रूण को 8 ब्लास्टोमियर से अधिक अवस्था पर परिवर्तन हेतु स्त्री के गर्भाशय में स्थानान्तरित किया जाता है तो इसे IUT कहते हैं । यदि किसी स्त्री में गर्भधारण नहीं हो पाता है तो उसकी सहायता के लिए पात्रे निषेचन अर्थात् अन्य स्त्री के भीतर ही निषेचन कराने के बाद भ्रूण को उस स्त्री में स्थानान्तरित किया जा सकता है।
• टेस्ट ट्यूब बेबी (Test tube baby)-इस विधि में दाता स्त्री के अण्डे को दाता पुरुष शुक्राणु से प्रयोगशाला में परखनली के भीतर (स्त्री शरीर के बाहर) निषेचन कराया जाता है तथा निश्चित समय तक अनुरूपी परिस्थितियों में परिवर्धन के बाद अग्रिम परिवर्धन हेतु स्त्री के गर्भाशय में स्थानान्तरित कर दिया जाता है। इस विधि द्वारा जन्मे बच्चे को “टेस्ट ट्यूब बेबी” कहते हैं।

2. युग्मक आन्तर फैलोपीयन स्थानान्तरण (Gamete intrafallopian transfer GIFT)-
जिन स्त्रियों में अण्डाणु उत्पन्न नहीं होता है किन्तु इनमें निषेचन और भ्रूण परिवर्धन के लिए उचित वातावरण होता है उनमें यह विधि अपनायी जाती है। इसमें एक दाता स्त्री से अण्डाणु लिया जाता है तथा उस स्त्री को फैलोपीयन नलिका में स्थानांतरित कर दिया जाता है।

3. आन्तर कोशिकीय शुक्राणु निक्षेपण (Intra-cytoplasmic sperm injection)-
प्रयोगशाला में भ्रूण बनाने के लिए इस प्रक्रिया में शुक्राणु को सीधे ही अण्डाणु में अंत:क्षेपित कर दिया जाता है।

4. कृत्रिम वीर्य सेचन (Artificial insemination AI)-
यदि पुरुष-स्त्री को वीर्य सेचित करने में अक्षम हो अथवा उसके वीर्य में शुक्राणुओं की संख्या कम हो तो ऐसी अवस्था में यह तकनीक अपनायी जाती है। इस विधि में पति अथवा एक स्वस्थ दाता का वीर्य कृत्रिम रूप से स्त्री की योनि में प्रविष्ट कर दिया जाता है। जब कृत्रिम विधि से वीर्य को गर्भाशय में प्रविष्ट किया जाता है तो इसे गर्भाशय वीर्य सेचन (Intra-uterine insemination IUI) कहते हैं।

5. परपोषी मातृत्व (Host mothering)-
इस विधि में भ्रूण को प्राकृतिक माता से निकालकर एक अन्य स्त्री धात्रेय माता (Foster mother) में रोपित कर दिया जाता है। धात्रेय माता में यह भ्रूण जन्म तक अथवा अस्थायी रूप से निश्चित समय तक वर्धित होता है। जिसके बाद इन्हें पुनः मूल माता में या अन्य किसी स्त्री में रोपित कर दिया जाता है। यह तकनीक ऐसी स्त्रियों के लिए लाभदायक है जिनमें भ्रूण बन तो जाता है किन्तु पूर्ण परिवर्धन के समय तक ये इसे रख नहीं पाती हैं।

प्रश्न 10.
किसी व्यक्ति को यौन संचारित रोगों की चपेट में आने से बचने के लिए कौन-से उपाय अपनाने चाहिए?
उत्तर
यौन संचारित रोगों से बचाव (Protection from Sexually Transmitted Diseases)यौन संचारित रोगों से बचाव हेतु निम्न बातों का ध्यान रखना चाहिए

1. किसी अनजान व्यक्ति या बहुत से व्यक्तियों के साथ यौन संबंध न रखें।
2. मैथुन के समय हमेशा कंडोम का इस्तेमाल करें।
3. संक्रमित व्यक्ति का रुधिर किसी अन्य व्यक्ति को न चढ़ाया जावे।
4. पहले से उपयोग किये गये इंजेक्शन व सुईयों का प्रयोग न करें।
5. समलैंगिकता से बचें।
6. यदि कोई आशंका है तो तुंरत ही प्रारंभिक जाँच के लिए किसी योग्य चिकित्सक से मिलें और रोग की पहचान होने पर पूरा इलाज करावें।

प्रश्न 11.
निम्न वाक्य सही है या गलत, व्याख्या सहित बताइए

(क) गर्भपात स्वतः भी हो सकता है। (सही/ गलत)
उत्तर
गलत, सामान्य परिस्थितियों में गर्भपात नहीं होता। किसी दुर्घटनावश या स्वैच्छिक रूप से गर्भसमापन (गर्भपात) होता है।

(ख) बंध्यता को जीवनक्षम संतति न पैदा कर पाने की अयोग्यता के रूप में परिभाषित किया गया है और यह सदैव स्त्री की असामान्यताओं/दोषों के कारण होती है।(सही/गलत)
उत्तर
गलत, बंध्यता हमेशा स्त्री की असामान्यताओं/ दोषों के कारण नहीं होती, कभी-कभी पुरुष भी बंध्यता के लिए दोषी होता है।

(ग) एक प्राकृतिक गर्भ निरोधक उपाय के रूप में शिशु को पूर्णरूप से स्तनपान कराना सहायक होता है। (सही/गलत)
उत्तर
सही, शिशु को पूर्णरूप से स्तनपान कराने से अण्डोत्सर्ग नहीं होता है। अतः आर्तव चक्र (Menstrual cycle) भी नहीं होता है, जिसके कारण गर्भ की संभावनाएँ समाप्त हो जाती हैं। किन्तु यह विधि शिशु के जन्म के अधिकतम 6 माह तक कारगर है।

(घ) लोगों के जनन स्वास्थ्य के सुधार हेतु यौन संबंधित पहलुओं के बारे में जागरुकता पैदा करना एक प्रभावी उपाय है।(सही/गलत)
उत्तर
सही, क्योंकि ऐसा करने से लोगों की जनन स्वास्थ्य की समस्याएँ समाप्त अथवा कमतर हो जाती हैं।

प्रश्न 12.
निम्नलिखित प्रश्नों को सही कीजिए

(क) गर्भ निरोधक के शल्य क्रियात्मक उपाय युग्मक बनने को रोकते हैं।
उत्तर
युग्मक बनने से नहीं, बल्कि युग्मकों के परिवहन को रोकते हैं।

(ख) सभी प्रकार के यौन संचारित रोग पूरी तरह उपचार योग्य हैं।
उत्तर
हिपेटाइटिस-B, एड्स एवं जननिक हर्पिस का उपचार नहीं होता।

(ग) ग्रामीण महिलाओं के बीच गर्भ निरोधक के रूप में गोलियाँ (पिल्स) बहुत अधिक लोकप्रिय
उत्तर
ग्रामीण महिलाओं में गर्भ निरोधक के रूप में गोलियाँ (पिल्स)लोकप्रिय नहीं हैं । ग्रामीण महिलाओं को यौन शिक्षा की आवश्यकता है।

(घ) ई. टी. तकनीकों में भ्रूण को सदैव गर्भाशय में स्थानान्तरित किया जाता है।
उत्तर
ई. टी. तकनीकों में 8 ब्लास्टोमियर से ज्यादा अवस्था वाले भ्रूण को गर्भाशय में स्थानान्तरित किया जाता है। जबकि 8 ब्लास्टोमियर से कम अवस्था वाले भ्रूण को अण्डवाहिनी में स्थानान्तरित किया जाता है।

जनन स्वास्थ्य अन्य महत्वपूर्ण प्रश्नोत्तर

जनन स्वास्थ्य वस्तुनिष्ठ प्रश्न

1. सही विकल्प चुनकर लिखिए-

प्रश्न 1.
स्त्रियों के शरीर से फैलोपियन ट्यूब को अलग करना कहलाता है
(a) वैसेक्टोमी
(b) ट्यूबेक्टोमी
(c) ओवरीक्टोमी
(d) कैस्ट्रेशन।
उत्तर
(b) ट्यूबेक्टोमी

प्रश्न 2.
आबादी की सर्वाधिक वृद्धि का प्रमुख कारण है
(a) कम मृत्यु दर
(b) जन्मदर में वृद्धि
(c) अकाल न पड़ना
(d) युद्ध कम होना।
उत्तर
(a) कम मृत्यु दर

प्रश्न 3.
बड़े शहरों में अधिक जनसंख्या का कारण है
(a) शिक्षा के अवसर
(b) उपलब्ध भौतिक सुविधाएँ
(c) अधिक आय के स्रोत
(d) उपर्युक्त सभी।
उत्तर
(d) उपर्युक्त सभी।

प्रश्न 4.
जनसंख्या घनत्व अधिक है____
(a) यू.एस.ए. में
(b) भारत में
(c) चीन में
(d) जापान में।
उत्तर
(c) चीन में

प्रश्न 5.
AIDS रोग फैलता है
(a) बैक्टीरिया से
(b) प्रोटोजोआ से
(c) वाइरस से
(d) फंगस से।
उत्तर
(c) वाइरस से

प्रश्न 6.
यौन संक्रमित रोगों के कारक होते हैं
(a) विषाणु
(b) जीवाणु
(c) प्रोटोजोआ
(d) उपर्युक्त सभी।
उत्तर
(a) विषाणु

प्रश्न 7.
भारत में जनसंख्या की गणना की गई थी
(a) सन् 1891
(b) सन् 1947
(c) सन् 1950
(d) सन् 1961.
उत्तर
(a) सन् 1891

प्रश्न 8.
निम्न में से जन्मदर को नियंत्रित करने की विधि
(a) TUD
(b) GIFT
(c) MIF
(d) IVEET
उत्तर
(a) TUD

प्रश्न 9.
एल्कोहॉल से सर्वाधिक प्रभावित अंग है
(a) यकृत
(b) सेरीब्रम
(c) सेरीबेलम
(d) हृदय।
उत्तर
(a) यकृत

प्रश्न 10.
विश्व की जनसंख्या वृद्धि दर है
(a) 2.4%
(b) 2%
(c) 3%
(d) 4%.
उत्तर
(b) 2%

2. रिक्त स्थानों की पूर्ति कीजिए

1. मानव जनसंख्या का सांख्यिकीय अध्ययन ………………. कहलाता है।
2. माल्थस के अनुसार जनसंख्या में ………………. वृद्धि होती है जबकि खाद्य उत्पादन में ……………….. वृद्धि होती है।
3. किसी समष्टि में एक निश्चित अवधि में जीवों का आना और बाहर जाना ………………. कहलाता
4. शुक्राणु नली को काटकर बन्द करना ………………. कहलाता है।
5. स्थलीय जीवों के जनसंख्या घनत्व के लिये स्थान के क्षेत्रफल को ……………… से प्रदर्शित करते हैं।
6. जन्मदर एवं अप्रवासन जनसंख्या घनत्व में ………………. करते हैं।
7. संशोधित जन्मदर ……………… जन्मदर से अधिक होती है।
8. जनसंख्या आकार को नियन्त्रित करने वाले कारक को …………….. कहते हैं।
9. जैव सूचकांक = ( ………………. / मृत्युदर) x 1000.
10. बालिकाओं में बालकों की अपेक्षा ……………. परिपक्वता आती है।
11. भारत पहला देश है जिसने …………………… स्वास्थ्य देखभाल को ………………….में सामाजिक लक्ष्य के रूप में लाया।
12. RCH भारत में .. ……………. में लाया गया।
13. एम्नियोसेन्टेसिस में लिंग निर्धारण …………. गुणसूत्र के निरीक्षण द्वारा लाया गया।
14. प्रसव के ठीक बाद महिलाएँ …… अनार्तव (मासिक धर्म amoeriorrhoea) का अनुभव करती हैं।
15. LNG-20 ……………….. स्रावी IUD है।
उत्तर

1. डेमोग्राफी
2. बीजगणितीय, अंकगणितीय
3. प्रवासन
4. वैसेक्टोमी
5. द्विविमा (m²)
6. वृद्धि,
7. अशोधित
8. धनात्मक अवरोधक
9. जन्मदर
10. जल्दी
11. प्रजनन, सन् 1951
12. सन् 1997,
13. लिंग
14. स्तनपान संबंधी
15. हॉर्मोन।

3. सही जोड़ी बनाइए

‘A’ – ‘B’

1. S-आकृति वक्र – (a) जन्म नियंत्रण विधि
2. kसीमा स्थिरांक – (b) जनसंख्या
3. शुक्राणु नाशक रसायन – (c) लॉजिस्टिक वक्र
4. माल्थस 2009 – (d) D/Px1000
5. वास्तविक मृत्युदर – (e) संतृप्ति अवस्था।
उत्तर
1.(c), 2.(e), 3.(a), 4. (b), 5.(d).

‘A’ – ‘B’

1. माल्थस – (a) कॉपर-टी
2 वैसेक्टोमी – (b) लिंग परीक्षण
3. ट्यूबेक्टोमी – (c) सेन्सस
4. जनगणना – (d) जनसंख्या पर निबंध
5. एम्निओसेण्टेसिस – (e) पुरुष
6. आई.ग.सी.डी. – (f) स्त्री या जनसंख्या नियंत्रण।
उत्तर
1.(d),2.(e),3. (1), 4.(c), 5.(b), 6.(a).

4. एक शब्द में उत्तर दीजिए

1. दो ऐसे कारण दीजिए जिनसे जनसंख्या अनियन्त्रित रूप से बढ़ जाती है।
2. IUCD का पूरा नाम लिखिए।
3. मानव जनसंख्या का अध्ययन क्या कहलाता है?
4. माला D और N में कौन-सा रासायनिक गर्भ-निरोधक पाया जाता है ?
उत्तर

1. (i) कम उम्र में विवाह, (ii) शिक्षा
2. इन्ट्रायूरिक कन्ट्रासेप्टिव डिवाइसेस
3. डेमोग्राफी (Demography)
4. एस्ट्रोजन एवं प्रोजेस्टीरॉन हॉमोन।

जनन स्वास्थ्य अति लघु उत्तरीय प्रश्न

प्रश्न 1.
परिवार नियोजन को अब किस नाम से जाना जाता है ?
उत्तर
परिवार नियोजन को अब “परिवार कल्याण” के नाम से जाना जाता है।

प्रश्न 2.
सेन्ट्रल ड्रग रिसर्च इन्स्टीट्यूट (CDRI) कहाँ अवस्थित है।
उत्तर
लखनऊ (उत्तरप्रदेश) में स्थित है।

प्रश्न 3.
कंडोम के उपयोग के कोई एक लाभ लिखिए।
उत्तर
कंडोम यौन संचरित रोगों से बचाव करता है।

प्रश्न 4.
हफ्ते में एक बार लेने वाली गर्भनिरोधक गोली का नाम लिखिए।
उत्तर
“सहेली”

प्रश्न 5.
IUCD काशब्द विस्तार बताइए।
उत्तर
इन्ट्रा यूटेराइन कॉन्ट्रासेप्टिव डिवाइस।

प्रश्न 6.
STD का सम्पूर्ण रूप लिखिये।
उत्तर
यौन संचारित रोग (Sexually Transmitted Diseases)।

प्रश्न 7.
विवाह की वैधानिक आयु स्त्री और पुरुष के लिए क्या सुनिश्चित है ?
उत्तर
स्त्री की आयु 18 वर्ष तथा पुरुष के लिए 21 वर्ष सुनिश्चित है।

प्रश्न 8.
दो STD के नाम लिखिए जो संदूषित रक्त से संचारित होते हैं।
उत्तर
(a) एड्स
(b) हिपेटाइटिस-BI

प्रश्न 9.
लैंगिक संपर्क से होने वाले कोई दो रोग बताइए।
उत्तर

• सूजाक (Gonorrhoea)
• सिफलिस (Syphilis)

प्रश्न 10.
HIV एवं AIDS का सम्पूर्ण रूप लिखिए।
उत्तर

• HIV—ह्यूमन इम्यूनोडेफीसिएन्सी वाइरस।
• AIDS- एक्वायर्ड इम्यूनोडेफीसिएन्सी सिन्ड्रोम।

प्रश्न 11.
ZIFT का पूरा नाम लिखिए।
उत्तर
युग्मनज अन्तः डिम्बवाहिनी स्थानान्तरण (Zygote Intra-fallopian Transfer)।

प्रश्न 12
पुरुष में नसबंदी की शल्य क्रिया का क्या नाम है ?
उत्तर
वैसेक्टोमी (Vasectomy)।

प्रश्न 13.
दो ऐसे कारण दीजिये जिनसे जनसंख्या अनियन्त्रित रूप से बढ़ जाती है।
उत्तर
रोगों का नियंत्रण, कृषि का विकास।

प्रश्न 14.
मानव जनसंख्या का अध्ययन क्या कहलाता है ?
उत्तर
डेमोग्राफी।

प्रश्न 15.
माला D और N में कौन-सा रासायनिक गर्भ निरोधक पाया जाता है ?
उत्तर
एस्ट्रोजन एवं प्रोजेस्ट्रॉन।

प्रश्न 16.
एम्नियोसेण्टेसिस विधि द्वारा किसका परीक्षण किया जाता है ?
उत्तर
भ्रूण का लिंग परीक्षण।

प्रश्न 17.
किसी इकाई क्षेत्रफल में पाई जाने वाली मानव संख्या कहलाती है ?
उत्तर
जनसंख्या घनत्व।

जनन स्वास्थ्य लघु उत्तरीय प्रश्न

प्रश्न 1.
परखनली शिशु कैसे प्राप्त किये जा सकते हैं ?
उत्तर
स्त्रियाँ जब गर्भधारण करने योग्य नहीं होती हैं, उस स्थिति में परखनली शिशु तकनीक का उपयोग किया जाता है। स्त्रियों के अनिषेचित अण्डाणु को ऐण्टिसेप्टिक स्थिति में निकाला जाता है। इस अण्डाणु को परखनली में लेकर शुक्राणु द्वारा निषेचन (Fertilization) की क्रिया कराते हैं । निषेचित अण्डाणु से विदलन क्रिया द्वारा 32 कोशिकीय अवस्था वाला भ्रूण बनता है, जिसे ब्लास्टोसिस्ट (Blastocyst) कहते हैं। इस 32 कोशिकीय भ्रूण का रोपण स्त्रियों के गर्भाशय में कर दिया जाता है जहाँ पर इस भ्रूण का अगला विकास होता है और शिशु बनता है जिसे ‘टेस्ट ट्यूब बेबी’ कहते हैं।

प्रश्न 2.
गिफ्ट (GIFT) क्या है ?
उत्तर
GIFT-इसका पूरा नाम गैमीट इन्ट्रा फैलोपियन ट्रान्सफर (Gamete Intra Fallopian Transfer) है । यह गर्भ निरोधन की आधुनिक तकनीक है। इस तकनीक में शुक्राणु कैथेटर (Catheter) में संगृहीत कर लिया जाता है। वाश स्विम तकनीक (Wash swim up technique) द्वारा शुक्राणुओं को अण्डाणु के पीछे कैथेटर में संगृहीत किया जाता है। यह सम्पूर्ण क्रिया स्त्रियों की फैलोपियन नलिका में होती है। निषेचन क्रिया शुक्राणुओं की संख्या कम होने से पूर्ण नहीं हो पाती है।

प्रश्न 3.
ट्यूबेक्टोमी और वैसेक्टोमी को समझाइये।
उत्तर
ट्यूबेक्टोमी-इसमें स्त्री की अण्डवाहिनी को काटकर बाँध दिया जाता है। जिससे अण्डाणु गर्भाशय में नहीं आ पाते और निषेचन नहीं हो पाता। इसे ट्यूबेक्टोमी कहते हैं। यह परिवार नियोजन की एक विधि है। वैसेक्टोमी-यह भी परिवार नियोजन की एक विधि है जो पुरुषों द्वारा अपनाई जाती है। इसमें पुरुष की शुक्राणु नलिका को काटकर बाँध दिया जाता है जिससे शुक्राणु स्खलन के समय नहीं निकलते और निषेचन नहीं हो पाता। यह क्रिया वैसेक्टोमी कहलाती है।

प्रश्न 4.
एम्नियोसेण्टेसिस क्या है ?
उत्तर
एम्नियोसेण्टेसिस भ्रूण परीक्षण की एक तकनीक है जिसमें सर्जिकल सुई द्वारा मादा के गर्भाशय से एम्नियोटिक द्रव को शरीर से बाहर निकाला जाता है और एम्नियोटिक द्रव में उपस्थित फोयटस कोशा का संवर्धन किया जाता है और इसका गुणसूत्रीय परीक्षण करके निम्न बातों का पता लगाया जाता है

• गुणसूत्रीय असामान्यता, जैसे-डाउन सिण्ड्रोम, फिलोडेल्फिया सिण्ड्रोम एवं एडवर्ड सिण्ड्राम।
• उपापचयी अनियमितताएँ, जैसे- PKU, क्रिटेनिज्म, एल्केप्टोन्यूरिया।
• लिंग भ्रूण के परीक्षण में इसका उपयोग किया जाता है।

प्रश्न 5.
मानव जनसंख्या वृद्धि के सामाजिक कारण समझाइये।
उत्तर
मानव जनसंख्या वृद्धि के प्रमुख सामाजिक कारण निम्नलिखित हैं

• समाज का अशिक्षित होना ।
• निम्न सामाजिक स्तर का होना।
• समाज में विभिन्न प्रकार की कुरीतियाँ होना।
• विभिन्न प्रकार की सामाजिक मान्यताएँ ।
• कम उम्र में विवाह करना, क्योंकि उम्र के पूर्वार्द्ध में प्रजनन क्षमता अधिक होती है।
• निम्न सामाजिक स्तर के कारण मनोरंजन का अभाव होना।
• सामाजिक मान्यताएँ जैसे-पुत्र रत्न की प्राप्ति से मोक्ष मिलता है
• सामाजिक पिछड़ापन।

MP Board Class 12th Biology Solutions

MP Board Class 12th Chemistry Solutions Chapter 6 General Principles and Processes of Isolation of Elements

General Principles and Processes of Isolation of Elements NCERT Intext Exercises

Question 1.
Which of the ores mentioned in Table 6-1 ? Can be concentrated by mag-netic separation method ?
Answer:
Magnetic ores are separated from non-magnetic impurities by magnetic separa¬tion method. For example, magnetic (anion ore) is separated from non-magnetic silica and other impurities by this method.

Question 2.
What is the significance of leaching in the extraction of aluminium ?
Answer:
Main ore of aluminium is bauxite (Al₂O₃ xH₂O). It contains the impurities of SiO₂, FeO and Titanium oxide (TiO₂). These impurities are removed by Leaching. The sig-nificance of leaching is to prepare pure alumina from bauxite. The powdered bauxite ore is heated with NaOH solution at 473 – 523K. Alumina dissolves as sodium meta aluminate whereas impurities of iron and titanium remains behind.

The impurities are filtered off. The filtrate is neutralized by passing CO₂. Aluminium hydroxide separates out while sodium silicate remains in the solution. Aluminium hydroxide on heating gives pure alumina.

Question 3.
The reaction,
Cr₂O₃ + 3Al → Al₂O₃ + 2Cr; (∆°G = -421 kJ)
is thermodynamically feasible as is apparent from the Gibb’s energy value. Why does it not take place at room temperature ?
Answer:
All the reactants and products are solid at room temperature. Therefore, reaction does not occur at room temperature. At high temperature reactants melt and react.

Question 4.
Is it true that under certain conditions, Mg can reduce SiO₂ and Si can reduce MgO ? What are those conditions ?
Answer:
Mg can reduce SiO₂ below or at 1693K. Silicon can reduce MgO above 1693K.

General Principles and Processes of Isolation of Elements NCERT TextBook Exercises

Question 1.
Copper can be extracted by hydrometallurgy but not zinc. Explain.
Answer:
Copper is comparatively less acitve metal as its reduction potential i.e. E° (Cu²⁺/Cu) is high (+0-34V). It can be displaced from solution of Cu²⁺ ions by more active metals which have E° value lower than copper. For example, E° of zinc (Zn²⁺/Zn) is -0.76V and thus, zinc can displace copper from solution of Cu²⁺ ions. In contrast to displace zinc from solution of Zn²⁺ ions a more reactive metal than zinc is required like, Na, K, Mg, Ca, etc. But, the more active metals readily react with water forming their corresponding ions and evolve hydrogen gas.
[2Na + 2H₂O → 2NaOH + H₂],
Thus, it is difficult to displace zinc from solution of Zn²⁺ ions. Elence, copper can be extracted by hydrometallurgy but not zinc.

Question 2.
What is the role of depressant in froath floatation process ?
Answer:
The role of depressant is to prevent one type of sulphide ore particles from forming the froth with air bubbles. NaCN is used as a depressant to separate lead sulphide (PbS) ore from zinc sulphide (ZnS) ore. NaCN forms a zinc complex, Na[Zn(CN)₄] on the surface of ZnS thereby preventing it from the formation of the froath.

Question 3.
Why is the extraction of copper from pyrites more difficult than that from its oxide ore through reduction ?
Answer:
The standard free energy (∆_fG°) of formation of Cu₂ S is more -ve than those of H₂S and CS₂. Therefore, Cu₂S cannot be reduced by carbon or H₂. The following two reactions do not occur. ∆_rG° for these reactions is positive.
Cu₂S + H₂ → 2Cu + H₂S;
2CU₂S + C → 4Cu + CS₂
In contrast ∆_fG° of Cu₂O is less -ve than that of CO and hence carbon can easily reduced Cu₂O to Cu.
Cu₂O_(s) + C_(s) → 2Cu + CO_(g)
It is because of this reason that the extraction of copper from pyrite is difficult than from its oxide ore.

Question 4.
Explain: (i) Zone refining, (ii) Column chromatography.
Answer:
(i) Zone refining (Fractional crystallization): This method is used to prepare metals in extremely pure state. Boron, gallium, indium, silicon, germanium etc. are purified by this method. This method is based on the fact that when molten impure metal is allowed to cool, the pure metal crystallizes out whereas the impurities remain behind in the melt.

Method: A thin bar of impure metal is taken. One zone of bar is heated with a moving circular heater in the atmosphere of an inert gas. A narrow zone of the metal is melted. The pure metal crystallizes out of the melt while the impurities move into the adjacent molten zone.

The process is repeated several times till the impurities are completely driven to one end and the pure metal towards the other end. Then end of the rod where the impurities have collected is cut off. The metal obtained is extremely pure.

(ii) Column chromatography: In column chromatography, a suitable adsorbent such as alumina (Al₂O₃) is packed in glass tube having a stop-cock near the bottom. This constitutes the stationary phase. The mixture to be separated is dissolved in some suitable solvents and added to the column. The different components of the mixture get adsorbed to different extent. Some suitable solvent (called eluent) is then added to the column. The eluent constitute the mobile phase. The weakly adsorbed component reaches the bottom of the column first.

It is followed by more strongly adsorbed components. Thus, different components of the mixture reach the bottom one by one and in this way get separated. This method is suitable for purification of those elements which are available in small quantities and the impurities are not much different in chemical behaviour from the element to be purified. Lanthanoides (rare earth elements) are purified by this technique.

Question 5.
Out of C and CO, which is a better reducing agent at 673 K ?
Answer:
When carbon reacts with dioxygen, two reactions are possible
C_(s) + O_2(g) → CO_2(g) ……(i)
2C_(s) + O_2(g) → 2CO_(g) …..(ii)
When CO is used as a reducing agent, it gets oxidized to CO₂
2CO + O₂ → 2CO₂ …(iii)
It is clear from the Ellingham diagram that at 673K the ∆G° for the oxidation of CO to CO₂ is more negative than the reaction (i) and reaction (ii). Therefore, CO is better reducing agent than C. It is supported by the fact that the curve for the reaction (iii) lies below the curve for the reaction (i) and reaction (ii) at 673K. An element below in Ellingham diagram reduces the oxide of other metal which lies above it.

Question 6.
Name the common elements present in the anode mud in electrolytic refining of copper. Why are they so present ?
Answer:
The common elements present in the anode mud are Ag, Au, Pt, Sb, Se etc. These elements are less reactive and not affected by CuSO₄ and H₂SO₄ solution and hence, settle down under anode as anode mud.

Question 7.
Write down the reactions taking place in different zones in the blast furnace during the extraction of iron.
Answer:
Reactions in blast furnace :
(i) Coke burns in presence of air to form CO₂ in excess of CO is formed.

(ii) CO reduces haematite ore (Fe₂O₃) to ferric oxide (FeO) at 600°C.
CO + Fe₂O₃ → 2 FeO + CO₂
(iii) About 750°C CO reduces FeO into Fe.
FeO + CO → Fe + CO₂
(iv) At 110° CaCO₃ decomposes into CaO.
CaCO₃ → CaO + CO₂
This way the iron sobtained is called spongy iron.
(v) CaO reacts with silica present in ore and form slag.
CaO + SiO₂ → CaSiO₃
calcium silicate
Slag floats over molten iron from where it is removed through the tapping hole.
Labelled diagram of blast furnace :

Question 8.
Write chemical reactions taking place in the extraction of zinc from zinc blende.
Answer:
Zinc oxide is obtained from zinc blende, then zinc is extracted from zinc oxide. The whole process is described below :
The zinc blende (ZnS) ore is concentrated by froth floatation process, then roasted to give oxide.
2ZnS + 2O₃ → 2ZnO + 2SO₂ ↑
The zinc oxide is mixed with coke and clay to make bricketters. These bricketters are heated at 1673 K to give zinc. The temperature in this case is higher than that in case of copper.

The metal is distilled off and collected by rapid chilling.
(Note : For detail, refer to Other Important Long Ans. Type Q. No. 7.)

Question 9.
State the role of silica in the metallurgy of copper.
Answer:
Silica acts as acidic flux in order to remove basic impurity of iron oxide.

Question 10.
What is meant by the term “Chromatography” ?
Answer:
Chromatography is a technique for the separation and purification based on the difference in the adsorbing tendencies of the metal and its impurities on a suitable adsorbent. It is based on the principle that different compounds of a mixture are differently adsorbed on an adsorbent. The terms is originally derived from the Greek word ‘Chroma’ meaning colour and ‘graphy’ for writing because it is first used to the colour plant pigments.

Question 11.
What criterion is followed for the selection of the stationary phase in chro-matography ?
Answer:
The stationary phase is selected in such a way that it is capable of adsorbing the impurities more strongly than the elements to be purified. Under this condition, the impurities are retained by stationary phase i. e„ these cannot be eluted easily while the pure component, which is weakly adsorbed is easily eluted.

Question 12.
Describe a method for refining nickel.
Answer:
Mond process : Nickel is refined by this method. Impure nickel is heated in a current of CO at 330-350 K. Volatile nickel carbonyl Ni(CO)₄ is formed while the impurities remain behind. Nickel carbonyl is now heated to 450-470 K. It decomposes to give pure nickel.

Question 13.
How can you separate alumina from silica in bauxite ore associated with silica ? Give equations, if any.
Answer:
Main ore of aluminium is bauxite (Al₂O₃ xH₂O). It contains the impurities of SiO₂, FeO and Titanium oxide (TiO₂). These impurities are removed by Leaching. The sig-nificance of leaching is to prepare pure alumina from bauxite. The powdered bauxite ore is heated with NaOH solution at 473 – 523K. Alumina dissolves as sodium meta aluminate whereas impurities of iron and titanium remains behind.

The impurities are filtered off. The filtrate is neutralized by passing CO₂. Aluminium hydroxide separates out while sodium silicate remains in the solution. Aluminium hydroxide on heating gives pure alumina.

Question 14.
Giving examples, differentiate between ‘Roasting’ and ‘Calcination’.
Answer:
Difference between Roasting and Calcination :
Roasting
Heating ore in the presence of air below its melting point. This is generally done for sulphide ore.
Calcination
Heating ore either in the presence or limited supply of air below its melting point. This is generally done for carbonate ore.

Question 15.
How is ‘cast iron’ different from ‘pig iron’ ?
Answer:
Iron obtained from blast furnace is called pig iron. It contains about 4% carbon and other impurities of S, P, Si, Mn etc. When pig iron is mixed with scrap iron and coke and then heated in a blast of hot air, some impurities are removed. Cast iron is obtained. It contains 3% carbon and some other impurities. It is hard and brittle.

Question 16.
Differentiate between “Minerals” and “Ores”.
Answer:
Differences between Minerals and Ores :
Minerals

1. Compounds of metals which contain less amount of metal and are found in in the earth’s crust with impurities are called mineral.
2. 0It is difficult to obtain metals in pure form from minerals.
   Example : Mica, Feldspar, Limonite etc.

Ores

1. Compounds of metals which contain sufficient amount of metal are known as ores.
2. Metals can be obtained easily in pure form from the ores.
   Example: Ores of Aluminium, Cryolite, Bauxite, Alunite etc.

Question 17.
Why copper matte is put in silica lined converter ?
Answer:
Copper matte contains Cu₂S and FeS. Copper matte is heated with silica to re-move the impurities of FeS as FeSiO₃ (slag).
2FeS + 3O₂ → 2FeO + 2SO₂
FeO + SiO₂ → FeSiO₃
Slag

Question 18.
What is the role of cryolite in the metallurgy of aluminium ?
Answer:
Cryolite serve the following two purposes :

1. It makes alumina a good conductor of electricity.
2. It lowers fusion temperature of electrolyte.

Question 19.
How is leaching carried out in case of low grade copper ores ?
Answer:
The leaching of the low grade copper ores is carried out with acids in the presence of air when copper goes into solution as Cu²⁺ ions. Thus,
2Cu + 2H₂SO₄ + O₂ → 2CUSO₄ + 2H₂O

Question 20.
Why is zinc not extracted from zinc oxide through reduction using CO ?
Answer:
In Ellingham diagram, the curve for the oxidation of CO to CO₂ lies above the curve for the oxidation of Zn. Therefore, CO cannot reduce ZnO to Zn. On the other hand, the curve for the oxidation of C to CO, lies below the curve for the oxidation of Zn at temperature 1120K or above. Therefore, ‘C’ can be used to reduce ZnO at 1120K or above this temperature.

Question 21.
The value of ∆_fG° for formation of Cr₂O₃ is -540 kJ mol^-1 and that of Al₂O₃ is -827 kj mol^-1. Is the reduction of Cr₂O₃ possible with A1 ?
Answer:

∆_rG° of the above reaction is -ve. Therefore Cr₂O₃ can be reduced by A1 to free chromium metal.

Question 22.
Out of C and CO, which is a better reducing agent for ZnO ?
Answer:
Carbon is better reducing agent. It has been explained in Q. No. 20.

Question 23.
The choice of a reducing agent in a particular case depends on thermody-namic factor. How far do you agree with this statement ? Support your opinion with two examples.
Answer:
The thermodynamic factor helps us in choosing a suitable reducing agent for the reduction of a particular metal oxide to metal. The feasibility of thermal reduction can be predicted on the basis of ∆_fG° vs T plots for the formation of oxides, known as Ellingham diagram. From the diagram, it can be predicted that metals for which ∆_fG° oxides is more negative can reduce those metal oxides for which the ∆_fG°, oxides is less negative. In other words, one will reduce the oxides of other metals which lie above in Ellingham diagram, because ∆_rG° of the combined redox reaction will be -ve by an amount equal to the difference in ∆_fG° of the two metal oxides. For example, Al can reduce Cr₂O3 but not MgO. Similarly C can reduce ZnO to Zn but not CO. Thus, the choice of a particular reducing agent depends upon thermodynamic factor.

Question 24.
Name the processes from which chlorine is obtained as a by-product. What will happen if an aqueous solution of NaCl is subjected to electrolysis ?
Answer:
Sodium metal is prepared by Down’s process. It involves the electrolysis of a fused mixture of NaCl and CaCl₂ at 873 k

If however, an aqueous solution of NaCl is electrolysed, H₂ is evolved at the cathode while Cl₂ is obtained at anode. The reason being \(\mathrm{E}_{\mathrm{Na}^{+} / \mathrm{Na}}^{\circ}\), (-2.71) is much lower than \(\mathrm{E}_{\mathrm{H}_{2} \mathrm{O} / \mathrm{H}_{2}}^{\circ}\) (-0.832) and hence water is reduced to H₂ in preference to Na⁺ ions.

Question 25.
What is the role of graphite rod in the electrometallurgy of aluminium ?
Answer:
In the electrolytic reduction of alumina, graphite anode facilitates reduction of Al₂O₃ to aluminium by electrolysis. Carbon reacts with oxygen liberated at anode producing CO and CO₂.

Question 26.
Outline the principles of refining of metals by the following methods:
(i) Zone refining
(ii) Electrolytic refining
(iii) Vapour phase refining.
Answer:
(i) Zone refining (Fractional crystallization): This method is used to prepare metals in extremely pure state. Boron, gallium, indium, silicon, germanium etc. are purified by this method. This method is based on the fact that when molten impure metal is allowed to cool, the pure metal crystallizes out whereas the impurities remain behind in the melt.

Method: A thin bar of impure metal is taken. One zone of bar is heated with a moving circular heater in the atmosphere of an inert gas. A narrow zone of the metal is melted. The pure metal crystallizes out of the melt while the impurities move into the adjacent molten zone.

The process is repeated several times till the impurities are completely driven to one end and the pure metal towards the other end. Then end of the rod where the impurities have collected is cut off. The metal obtained is extremely pure.

(ii) Electrolytic refining : This method is based upon the phenomenon of electroly-sis. The crude metal is made anode whereas the thin sheet of pure metal is made cathode.

Electrolyte is dissolved in the solution of some salt of the metal. On passing electricity the metal from the anode goes into the solution as ions due to oxidation while pure metal gets deposited at the cathode due to reduction of metal ions. The less electropositive impurities settle down below the anode as anode mud.

(iii) Vapour phase refining : The crude metal is heated with a specific reagent to obtain a volatile compound at lower temperature. The volatile compound is then heated at a higher temperature. The volatile compound decomposes at the higher temperature to give the metal Ni, Ti, Zr etc. are purified by this method.

(a) Mond process : Nickel is refined by this method. Impure nickel is heated in a current of CO at 330-350 K. Volatile nickel carbonyl Ni(CO)₄ is formed while the impurities remain behind. Nickel carbonyl is now heated to 450-470 K. It decomposes to give pure nickel.

(b) Van Arkel method: By this method ultrapure metals are obtained. In this method, the metal is converted into a volatile unstable compound (e.g., iodide). The impurities re main behind. The unstable volatile compound is collected and it is then decomposed to get the pure metal. Titanium and Zirconium are purified by this method. These metals are used in space technology.

Question 27.
Predict conditions under which Al might be expected to reduce MgO.
Answer:
Above 1623K, Al can reduce MgO in Mg.

Al₂O₃ is more stable than MgO, hence Al reduces MgO above 1623K.

General Principles and Processes of Isolation of Elements Other Important Questions and Answers

General Principles and Processes of Isolation of Elements Objective Type Questions

Question 1.
Choose the correct answer :

Question 1.
Cryolite is mixed during the electrolysis of alumina because it:
(a) Decreases the m.p. of alumina
(b) Decreases electrical conductance
(c) Separates the impurity of alumina
(d) Decreases anode effect.

Question 2.
Which of the following metal is preserve by the film of its own oxide :
(a) Ag
(b) Fe
(c)Cu
(d) Al.

Question 3.
Which method is applicable for the extraction of Al from bauxite :
(a) Reduction by Mg
(b) Reduction by coke
(c) Electrolytic reduction
(d) Reduction by Fe.

Question 4.
The bauxite containing impurity of iron oxide is purified by :
(a) Hoop’s method
(b) Serpeck’s process
(c) Bayer’s process
(d) Electrolytic process.

Question 5.
Blister copper is:
(a) Ore of copper
(b) Alloy of copper
(c) Pure copper
(d) Copper containing 1% impurities.

Question 6.
In blast furnace iron oxide is reduced by :
(a) SiO₂
(b) CO
(c) C
(d) CaCO₃.

Question 7.
In the extraction of Fe from haematite, lime stone acts as :
(a) Reducing agent
(b) Slag
(c) Gangue
(d) Flux.

Question 8.
Cupellation is used in the metallurgy of:
(a) Cu
(b) Ag
(c) Al
(d) Fe

Question 9.
Which is the essential part of photographic plates and films :
(a) AgNO₃
(b)Ag₂S₂O₃
(c) AgBr
(d) Ag₂CO₃.

Question 10.
The compound obtained by the reaction of Zn with the excess of caustic soda :
(a) Zn(OH)₂
(b) ZnO
(c) Na₂ZnO₂
(d) ZnH₂.

Question 11.
Calomel is:
(a) Hg₂Cl₂
(b) HgCl₂
(c) Hg₂Cl₂ + Hg
(d) Hg + HgCl₂.

Question 12.
Is formed on adding potassium iodide solution in excess amount of mercuric iodide:
(a) Hg₂Cl₂
(b) K₂HgI₄
(c) Hg
(d) Hg + KI₃.

Question 13.
The colour obtained by the mixing of excess of KI in to HgCl₂ solution:
(a) Orange
(b) Brown
(c) Red
(d) Colourless.

Question 14.
Which metal does not form amalgum :
(a) Zn
(b) Cu
(c) Mg
(d) Fe.

Question 15.
Malachite is:
(a) Cu₂S
(b) CUCO₃.CU(OH)₂
(c) Cu₂O
(d) CuCO₃.

Question 16.
AgBr is soluble in hypo because its forms :
(a) Ag₂SO₃
(b) Ag₂S₂O₃
(c) [Ag(S₂O₃)]^–
(d) [Ag(S₂O₃)₂]^3-

Question 17.
AgCl is soluble in ammonia due to the formation of:
(a) [Ag(NH₃)₄]⁺
(b) [Ag(NH₃)₂]²⁺
(c) [Ag(NH₃)₄]³⁺
(d) [Ag(NH₃)₂]⁺.

Question 18.
When KI mixed with solution of CuSO₄, it form :
(a) Cul₂
(b) Cul^-2₂
(c) K₂[CUI₄]
(d) Cu₂I₂ + I₂.

Question 19.
When KCN reacts with solution of CuSO₄, it forms :
(a) CU(CN)₂
(b) CuCN
(c) K₂[Cu(CN)₄]
(d) K₃[Cu(CN)₄]

Question 20.
Na₂S₂O₃ used in photography as a :
(a) Reducing agent
(b) Developer
(c) Fixer
(d) Tonning agent.

Answers:
1. (a), 2. (d), 3. (c), 4. (c), 5. (d), 6. (b), 7. (d), 8. (b), 9. (c), 10. (c), 11. (a), 12. (b), 13. (c), 14. (d), 15. (b), 16. (c), 17. (d), 18. (d), 19. (d), 20. (c).

Question 2.
Fill in the blanks :

1. Malachite is an ore of ……………..
2. In stainless steel, along with iron …………….. and …………….. metals form alloys.
3. …………….. is used as a purgative.
4. Colloidal solution of …………….. is used as a medicine of eyes.
5. AgNO₃ is known as ……………..
6. Chemical formula of corrosive sublimate is ……………..
7. Froath floatation process is generally employed for …………….. ores.
8. The process in which metal oxide is reduced by A1 is known as ……………..
9. Is used for drying ammonia ……………..
10. …………….. is called lunar caustic.
11. The chemical formula of fluorspar is ……………..
12. Alkaline solution of HgCl₂ and KI is known as ……………..
13. Red hot steel is slowly cooled when it gets converted to soft steel, this is known as ……………..

Answers:

1. Cu
2. Cr, Ni
3. Calomel
4. Ag
5. Lunar caustic
6. HgCl₂
7. Sulphide
8. Alum- inothermic
9. CuO
10. Silver Nitrate
11. CaF₂
12. Nesseler’s reagent
13. Annealing.

Question 3.
Match the following :

I.

Answers:

1. (g)
2. (d)
3. (c)
4. (e)
5. (b)
6. (a)
7. (f).

II.

Answers:

1. (d)
2. (f)
3. (b)
4. (e)
5. (c)
6. (a).

III.

Answers:

1. (d)
2. (e)
3. (f)
4. (c)
5. (b)
6. (a).

Question 4.
Answer in one word / sentence :

1. The mixture of Cu₂S and FeS obtained from blast furnace is known as.
2. Which metal is purified by polling?
3. After developing which solution is used for the fixing of photographic films?
4. Chemical formula of philosophers’s wool is.
5. Chemical formula of horn silver.
6. Which compound is normally used for toning in photography?
7. Which are known as coinage metals?
8. Give the name of ore used for extraction of Cu.
9. Give the name of ore used for extraction of Iron.
10. What is the name of graph which is drawn between the absolute temperature and standard free energy change for formation of metal oxide?
11. What is the name of iron obtained after the removal of impurities from cast iron?
12. What is the method of slow cooling of hot hard steel known as?
13. What is the method of heating hard steel known as?
14. What iš the method of heating steel in pressure of ammonia known as?
15. What is Lunar Caustic?

Answers:

1. Matte
2. Copper
3. Hypo solution (Na₂S₂O₃)
4. ZnO
5. AgCl
6. Aurric chloride
7. Cu, Ag and Au
8. Copper pyrite
9. Haematite
10. Ellinghum diagram
11. Wrought iron
12. Annealing
13. Softening
14. Nitriding
15. AgNO₃.

General Principles and Processes of Isolation of Elements Very Short Answer Type Questions

Question 1.
Cryolite is added during the electrolysis of alumina to obtain aluminium. Give reason.
Answer:
Melting point of Alumina is very high (2050°C). By adding cryolite, melting point of alumina is lowered as well as electrolysis becomes easier.

Question 2.
When Al is placed in contact with cone. HNO₃, then no reaction seems to take place. Why ?
Answer:
Since, Al reacts with HNO₃ to form Al₂O₃ which forms a protective layer on the metal by which reaction do not proceed further.

Question 3.
Which compound of A1 is a good reducing agent ?
Answer:
Complex hydride Li[AlH₄] of Al is mainly a good reducing agent for organic compounds.

Question 4.
Write the chemical formula of the following :

1. Calomel
2. Lunar caustic
3. Philosopher’s wool
4. Corrosive sublimate.

Answer:

1. Calomel: Mercurous chloride (Hg₂Cl₂)
2. Lunar caustic : Silver nitrate (AgNO₃)
3. Philosopher’s wool: Zinc oxide (ZnO)
4. Corrosive sublimate : Mercuric chloride (HgCl₂).

Question 5.
Write the main ores of copper.
Answer:
Main ores of copper are as follows :
1. Oxide: Cuprite or Ruby copper (Cu₂O)
2. Carbonate:Azurite – 2CuCO₃.Cu(OH)₂
Malachite – CuCO₃.Cu(OH)₂ or CuCO₃.CuO.H₂O
3. Sulphide: Copper pyrites or Calcopyrite – Cu₂S + Fe₂S₃ or CuFeS₂
Copper glance or Calcocite – Cu₂S.

Question 6.
Give the chemical name, formula and two application of lunar caustic.
Answer:
Chemical name of lunar caustic : Silver nitrate (AgNO₃)
Applications : It is used for 1. Silvering of mirror. 2. Making marking inks and hair dyes.

General Principles and Processes of Isolation of Elements Short Answer Type Questions

Question 1.
Explain following process of steel:
(a) Annealing
(b) Hardening
(c) Tempering
(d) Nitriding.
Answer:
(a) Annealing: It is process of heating steel to redness followed by slow cooling due to this steel becomes soft and pliable.
(b) Hardening or Quenching: It is a process of heating steel to redness followed by sudden cooling by plunging the red hot steel into water or oil. Steel becomes brittle and hard.
(c) Tempering : It is a process of heating the hardened or quenched steel to a temperature much below redness (200-350°C) followed by slow cooling steel loses its brittleness completely or partially depending upon time and temperature.
(d) Nitriding : Formation of a layer of iron nitride by heating steel at 500-600°C in chamber of ammonia for 3-4 days is called nitriding. Steel becomes harder by this treatment.

Question 2.
Write method of preparation of copper sulphate (Blue vitriol) and its use.
Answer:
Method of preparation of copper sulphate :
1. By heating copper with dilute H₂SO₄ in the presence of air.
2Cu + 2H₂SO₄ + O₂ → 2CUSO₄ + 2H₂O

2. By the action of H₂SO4 on copper oxide, hydroxide or carbonate :
CuO + H₂SO₄ → CuSO₄ + H₂0
CU(OH)₂ + H₂SO₄ → CuSO₄ + 2H₂O
CuCO₃ + H₂SO₄ → CuSO₄ + H₂O + CO₂
Uses : (1) In dying and printing textile, (2) As a bacteriocidal, (3) As an insectiside, (4) In electrical cells.

Question 3.
Give the chemical reaction when CuSO₄ solution reacts with :
(i) NaOH solution
(ii) NH₄OH
(iii) KI solution
(iv) KCN.
Answer:
(i) It forms light blue precipitate of cuprichydroxide.
CuSO₄ + 2NaOH → Cu(OH)₂ + Na₂SO₄
(ii) It forms deep blue colour solution which is due to the formation of cupric ammonium sulphate complex.
CuSO₄ + NH₄OH → [CU(NH₃ )₄ ]SO₄ + 4H₂O
(iii) It liberates iodine.
CuSO₄ + 2 KI → K₂SO₄ + Cul₂
2CUI₂ → I₂ + Cu₂I₂
(iv) It forms potassium cupracyanide.

Question 4.
What is blue vitriol ? What is the effect of heat on it?
Answer:
Commercial name of blue vitriol is blue vitriol which contain five molecules of water of crystallization. ¡t is a blue coloured crystalline solid soluble in water.

Effect of heat : On heating 100°C it loses 4 molecules of water of crystallization. At 230°C, it loses 5^th molecules of water and becomes white amorphous powder. The white powder again becomes blue in presence of water. It undergoes dissociation on strong heating.

Question 5.
What are the main ores of Al ? How can impure aluminium ¡s purified?
Answer:
Main ores of Al:
I. Bauxite – Al₂O₃.2H₂O
2. Felspar – K₂O.Al₂O₃.6H₂O
3. Cryolite – Na₃AIF₆
Electrolytic refining of aluminium (Hoope’s electrolytic process): Aluminium is further purified by Hoope’s process. Process is carried out in an iron cell lined inside with carbon. The cell consist of three layers which differ in specific gravities. The lowest layer acting as anode consists of impure aluminium. A mixture of fluorides of Al, Ba and Na forms middle layer and acts as electrolyte. The uppermost layer is of pure aluminium and it acts as anode.

Following changes occur on passing electric current:

On electrolysis, aluminium ions of the electrolyte are discharged at cathode and pure aluminium collects as the uppermost layer. An equivalent amount of aluminium is taken up by the middle layer from the bottom layer. Thus, aluminium is transferred from bottom layer to the upper layer through the middle layer while impurities are left behind. Crude aluminium is added from time to time to continue the process. Thus 99-98% pure aluminium is obtained.

Question 6.
Differentiate between cast iron, wrought iron and steel.
Answer:
Differences between Cast Iron, Wrought Iron and Steel:

Question 7.
Give names and formula of any two ores of following metals :
(i) Al
(ii) Zn
(iii) Fe
(iv) Cu
(v) Ag.
Answer:

Question 8.
Write four different chemical reactions of copper with nitric acid. Give equations also.
Answer:
Chemical reaction of Cu with HNO₃:
(a) With cold and very dilute nitric acid, nitrogen gas is evolved.
5Cu + 12HNO₃ → 5CU(NO₃)₂ + 6H₂O + N₂

(b) With hot and dilute Nitric acid, nitrous oxide is obtained.
4CU + 10HNO₃ → 4CU(NO₃)₂ + N₂O + 5H₂O

(c) With 50% HN03, Nitric oxide is formed.
3Cu + 8HNO₃ → 3CU(NO₃)₂ + 2NO + 4H₂O

(d) With cone. HNO₃, Nitrogen peroxide is obtained.
CU + 4HNO₃ → CU(NO₃)₂ + 2NO₂ + 2H₂O.

Question 9.
Write the name of three alloys of copper and give the composition and one use of each.
Answer:
Alloys of copper, their composition and uses are given ahead :

Question 10.
Explain why a bulb placed in parallel series to the electrical circuit for extraction of Al from Al₂O₃ ?
Answer:
In the extraction of Al form Al₂O₃ by electrolysis. Al₂O₃ converted into Al with decrease in concentration of electrolyte bulb placed in parallel glass indicating that cell resistance has increased. Therefore, more alumina is added at this stage and carbon rods are also replaced.

Question 11.
Explain the purification of bauxite with chemical equations.
Answer:
Baeyer’s process applied for the purification of bauxite ore containing ferric oxide as chief impurity. This ore is usually red in colour and hence called red bauxite.

The powdered ore is roasted first to convert ferrous oxide. If any, to ferric oxide and then digested with a concentrated solution of sodium hydroxide under pressure at 150°C for several hours. Alumina dissolves in sodium hydroxide forming soluble sodium meta aluminate (NaAlO2) while ferric oxide and silica being insoluble settles down and are removed by filtration.

Sodium meta aluminate is then agitated with freshly precipitated Al(OH)₃ for 36 hours. As a result sodium meta aluminate gets hydrolysed forming precipitate of aluminium hydroxide.

The precipitate is washed, dried and ignited to get pure alumina while solution of NaOH is concentrated and used again.

Question 12.
Give equation for the Auto-reduction process of copper pyrite to obtain pure copper.
Answer:
Molten matte obtained by smelting is mixed with sand and taken in a Bessemer converter and air is blown through tuyers when FeS gets converted to FeO which reacts with SiO₂ to form slag (FeSiO₃) and some part of Cu₂S gets oxidized to Cu₂O.
2FeS + 3O₂ → 2FeO + 2SO₂
2FeO + 2SiO₂ → 2FeSiO₃
2Cu₂S + 3O₂ → 2Cu₂O + 2SO₂
Which reacts with the remaining Cu₂S and gets reduced to metallic copper. This is known as Auto-reduction.
2CU₂O + Cu₂S → 6Cu + SO₂

Question 13.
How many type of iron is found ? Give the name of each and two characteristics of each.
Answer:
Iron is of three types : 1. Cast Iron, 2. Wrought Iron, 3. Steel.
Characteristics 1. Cast Iron : (i) It consists of 2-5 to 4-5% carbon.
(ii) It is very hard and its melting point is 1200°C.

2. Wrought Iron : (i) It consists of 0-12 to 0-25% carbon.
(ii) It is soft and its melting point is 1500°C.

3. Steel: (i) It consists of 0-5 to 1 -5% carbon.
(ii) It is normally hard and melting point is nearly 1300°C.

Question 14.
Describe the purification method of bauxite having silica as impurity.
Answer:
Serpeck’s process : This process is used when bauxite ore contains consider-able amount of silica as impurity. In this process ore mixed with coke is heated to 1800°C in presence of nitrogen. Alumina gets converted into aluminium nitride, AIN.
Al₂O₃ + 3C + N₂ → 2 AIN + 3CO
Silica gets reduced to silicon which volatilises at this temperature.
SiO₂ + 2C → Si + 2CO
AIN is hydrolysed to aluminium hydroxide by water.
AIN + 3H₂O → Al(OH)₃ + NH₃
As usual aluminium hydroxide is converted into alumina.

General Principles and Processes of Isolation of Elements Long Answer Type Questions

Question 1.
Write note on photography.
Answer:
The process of producing an exact impression of an object on an art paper by using light is called photography.
Modern photography involves following steps :

(i) Preparation of sensitive plate or film : A paste of colloidal silver bromide or silver iodide in gelatin is the sensitive emulsion. It is prepared by adding ammonium silver nitrate solution to ammonium bromide solution containing gelatin.

This is allowed to stand in a warm room for sometime when silver bromide particle grow in size and at the sametime becomes more sensitive to light.

(ii) Exposure : The sensitive plate or film is mounted in a camera and exposed for a few second to the image of properly focussed object. The light reduces silver bromide to extremely small particles of silver.
2 AgBr → 2Ag + Br₂
Inverted image of the object which is formed on the plate is not visible and is therefore called latent image.

(iii) Developing : The exposed film or plate is immersed in a solution of developer. Developer is a weak reducing agent such as potassium ferrous oxalate or an alkaline solu-tion of organic reducing agents like pyrogallol or quinol.

When the plate dipped in developing bath, the parts affected by light are reduced to maximum extent while part not affected by light remain unattached by the developer.

The plate is therefore called negative plate.

(iv) Fixing : Sodium thiosulphate is used in fixing negative plates. Negative plate is washed and dipped in a hypo, it dissolves unaffected silver bromide and leaves metallic silver unchanged.

(v) Printing (Printing out paper or P.O.P.): Coated with silver chloride and silver citrate mixture. The process is slow and can be watched and controlled when the image of required shade is obtained, it is fixed and toned.

Question 2.
What is Blister copper ? Describe with labelled diagram of its purification by electrolysis.
Answer:
Copper is removed by inverting Bessemer converter. The metal thus obtained contains sufficient quantity of SO₂. On cooling, SO₂ comes out from the metal in the form of bubbles producing small blisters on the metal surface. The metal is 98% pure and is called Blister copper.

Purification of copper by electrolysis : Mixture of 15% CUSO₄ and 5% H₂SO₄ is taken in a big tank which is fitted with thick plates of copper which act as anode. Plates of pure copper act as cathode. On passing electric current the impure metal dissolves at anode and goes into solution and pure metal from solution starts depositing at cathode. The impurities of Pt, Au and Ag settle down as anode mud. The impurities of Ni, Fe, Zn remain in the solution. Metal of 99-99% purity is obtained by this method.

Question 3.
Explain Siemen-Martin open hearth process for the manufacture of steel.
Answer:
Siemen-Martin’s open hearth process : The mixture of cast iron (30 – 50%), scrap iron haematite (Fe₂O₃) and lime is melted in the open hearth furnace which has a basic or acidic lining depending upon impurities. Fe₂O₃ acts as oxidizing agent in the formation of steel and carbon gets oxidized to CO and escapes

Fe₂O₃ + 3C → 3CO + 2Fe
2Fe₂O₃ +3S → 4Fe + 3SO₂
10F₂2O₃ + 3P₄ → 20Fe + 6P₂O₅
2Fe₂O₃ + 3Si → 4Fe + 3SiO₂
Fe₂O₃ + 3Mn → 2Fe + 3MnO
Now steel containing required amount of carbon is obtained by addition of spiegel.

Advantages :

1. As the process proceeds slowly therefore, its control is easy.
2. Better quality of steel can be manufactured.
3. The composition and temperature can be easily controlled.
4. As no blast of air is passed therefore, very little steel is lost.
5. The steel can be directly obtained by the use of ore and scrap iron.

Question 4.
Write the names and formula of two ores of silver and describe the method of extraction of Ag from any ore.
Or
Write the names and formula of the two ores of silver and describe the cyanide method for the extraction of Ag.
Answer:
Two ores of silver: (i) Argentite or Silver glance – Ag₂S.
(ii) Horn silver or Silver chloride – AgCl.

Extraction of silver by cyanide process (Mac Arthur Forest Process):
Silver metal is extracted from the Argentite ore (Ag₂S) by cyanide process.
It is a modern process and based on the following principle :

1. Silver reacts with the cyanides of alkal metals and forms a soluble complex.
2. Impurities do not react with alkali cyanides.
3. More electropositive metals (like zinc and aluminium) displace silver from its complex cyanides.

The process involves the following steps :
1. Crushing and concentration: The ore is crushed and then finely powdered in ball mills. It is then subjected to the froath floatation process for concentration.

2. Treatment of the ore with sodium cyanide : The concentrated ore is treated with a dilute solution (about 0-5%) of sodium cyanide for several hours. The solution is continuously agitated by passing a current of air. Silver sulphide goes into the solution in the form of soluble complex.

The reaction is reversible. Hence, Na₂S must be removed so that the reaction may proceed in the forward direction.
The air blown in oxidizes the sulphide formed to thiosulphate and sulphate and thus enables the reaction to proceed in the forward direction.

3. Precipitation of silver : The above solution is filtered to remove insoluble impurities. It is then treated with zinc dust. Silver being less electropositive, gets displaced by more electropositive zinc and is precipitated.

Uses of silver glance :
(i) In silver plating on metallic articles e.g., tableware and silvering of mirrors
(ii) Used in medicine.

Question 5.
Explain the composition, uses of alloys of :
(i) Aluminium
(ii) Copper
(iii) Iron.
Answer:
Composition and uses of alloys of given elements :

Question 6.
Write the principle of extraction of copper from copper pyrite.
Or, Explain extraction of copper under the following heads :
(a) Smelting
(b) Bessemerization.
Answer:
Principle : Copper pyrite is mixed ore of copper and iron. As sulphur has got more affinity for copper. Therefore on heating the ore first iron oxide is formed which is removed completely and then sulphur is extracted.
Process involves following steps :
(i) Concentration : By froath floatation process, powdered ore is taken in tank containing water and palm or eucalyptus oil. Air stream is passed, sulphide ore form froth which can be removed and impurity settles down.

(ii) Roasting : Concentrated ore is heated in the presence of air in a reverberatory furnace, sulphide ore is converted into oxides.
2CuFeS₂ + O₂ → 2FeS + Cu₂S + SO₂
2Cu₂S + 3O₂ → 2CU₂O + 2SO₂
2FeS + 3O₂ → 2FeO + 2SO₂

(iii) Smelting : Roasted ore is mixed with coke sand and acidic flux and smelted in blast furnace of 15-20ft height following reaction takes place:
Cu₂O + FeS → Cu₂S + FeO
FeO + SiO₂ → FeSiO₃ (Slag)
flux slag
At last matte is obtained which is a mixture of cuprous sulphide and small quantity of ferrous sulphide.

(iv) Bessemerization : Matte is mixed with little sand and melted in oval shape Bessemer converter lined with CaO or MgO. Here cuprous sulphide first converted into cuprous oxide which on reduction (autoreduction) gives copper.
2FeS + 3O₂ → 2FeO + 2SO₂
FeO + SiO₂ → FeSiO₃(slag)
2Cu₂S + 3O₂ → 2Cu₂O + 2SO₂
Cu₂S + 2Cu₂O → 6Cu + SO₂

Metal obtained contains SO₂ on cooling SO₂ comes out from the metal in the form of bubbles producing blisters on the metal surface called blister copper.

(v) Purification (By electrolytic method) : Thin strip of pure copper is taken as cathode and thick strip of impure copper is taken as anode. CuSO₄ as electrolyte when electric current is passed pure copper get deposited at cathode.

Question 7.
What are the main ores of Zn ? Describe the vertical retort method for the extraction of Zn.
Or,
Describe the modern method for the extraction of Zn.
Answer:
Main ores of Zn:
(i) Zinc blende – ZnS
(ii) Calamine – ZnCO₃
(iii) Willemite – ZnSiO₄.
Extraction : Zinc is extracted from its ore by two methods :
1. Reduction process
2. Electrolytic process.

1. Reduction Process : It involves the following steps :
(i) Concentration : Zinc blende is concentrated by froath floatation process while calamine ore is concentrated by gravity separation process. Iron oxide if present in ore is removed by magnetic separation.
(ii) Roasting : Concentrated ore is heated at about 900°C in excess of oxygen. Zinc sulphide is oxidised to zinc oxide.
2ZnS + 3O₂ → 2ZnO + 2SO₂
A portion of ZnS is also oxidised to zinc sulphate but it decomposes at 900°C into ZnO
ZnS + 2O₂ → ZnSO₄
2ZnSO₄ → 2ZnO + 2SO₂ + O₂
In case of calamine ore, calcination is done instead of roasting.
ZnCO₃ → ZnO + CO₂
(iii) Reduction : Roasted or calcined ore is mixed with coke and heated to 1400°C. Ore gets reduced into the metal.
ZnO + C → Zn + CO.

Reduction can be done by the following method :

Vertical retort process : Process carried out in vertical retort is continuous. Vertical retorts are made up of highly refractory silicon carbide bricks capable of with standing high temperature. Heating is done externally using producer gas. A screw conveyer is provided in the extension at the bottom for the removal of ash. Just near the top an outlet is there. It is connected with condenser. Roasted ore and coke is fed into the retort through the charging door. Vapour of zinc along with CO passes into the condenser where zinc condenses while CO escaping out is used as fuel for heating the furnace. Zinc is removed periodically from the condenser.

Question 8.
What happens when (Give only equations):
(i) Blue vitriol is heated.
(ii) Ammonium hydroxide is added to silver nitrate solution.
(iii) Mercuric chloride is added to stannous chloride solution.
(iv) Copper reacts with hot and concentrated sulphuric acid.
(v) Mercuric chloride reacts with potassium iodide.
(vi) Silver nitrate reacts with hydrochloric acid.
(vii) AgNO₃ is heated.
Answers:

Question 9.
Explain with labelled diagram the method of electrolysis to obtain pure aluminium metal.
Answer:
Electrolysis of alumina (Hall-Heroult process) : Electrolysis of alumina is done in an iron tank fitted with a lining of gas carbon which acts as cathode. Graphite rods act as anode and a bulb is fitted in parallel as indicator for alumina content. The electrolyte is a mixture of alumina and cryolite (Na3AlF6). The melting point of alumina is very high (2050°C). But, in presence of cryolite (Na₃AlF₆) and fluorspar (CaF₂), it melts at 870°C. Then pure alumina is added to the tank which dissolves in cryolite mixture.

Reaction : Reactions take place as below :
Na₃AlF₆ → 3NaF + AlF₃
AlF₃ → Al+3 +3F^–
3F^– → 3e^– + 3F (oxidation) at anode
Al³⁺ + 3e^– → Al (reduction) at cathode
2Al₂O₃ +12F → 4AlF₃ + 3O₂ ↑
The reaction proceeds continuously. When amount of Al₂O₃ decreases resistance of electrolyte increases and the bulb in the parallel glows up. Therefore at this junction more alumina is added. The Al liberated at cathode collects at the bottom of the tank in molten state which is taken out through the exit. Coke is added to the mixture of cryolite and alumina which does not allow it to cool and further protects the eyes from light. 99% pure aluminium metal is obtained by this process.

MP Board Class 12th Chemistry Solutions

MP Board Class 12th Biology Solutions Chapter 7 Evolution

Evolution NCERT Textbook Questions and Answers

Question 1.
Explain antibiotic resistance observed in bacteria in light of Darwinism selection theory.
Answer:
Darwinism theory of natural selection states that environment selects organisms with favourable variations and these organisms thus, survive and reproduce. It is observed when bacterial populations are exposed to certain antibiotic, the sensitive bacteria could not tolerate and hence, died due to the adverse environment. Whereas some bacteria that developed mutation became resistant to the particular antibiotic and survived. As a result such resistant bacteria survive and multiply quickly as compared to other sensitive bacteria. So, the whole population is regained by multiplication of resistant variety and antibiotic resis¬tant gene becomes widespread in the bacterial population.

Question 2.
Find out from newspapers and popular science articles any new fossil dis-coveries or controversies about evolution.
Answer:
Fossils of dinosaurs have revealed the evolution of reptiles in Jurassic period. As a result of this evolution of other animals such as birds and mammals has also been discovered. However, two unusual fossils recently unearthed in China have ignited a controversy over the evolution of birds confiiciusomis is one such genus of primitive birds that were crow sized and lived during the Cretaceous period in China.

Question 3.
Attempt giving a clear definition of the term species.
Answer:
A species generally includes similar organism. Members of this group can show interbreeding. Similar group of genes are found in the members of same species and this group has capacity to produce new species. Every species has some cause of isolation which intruped the interbreeding with nearest reactional species which is refer as reproductively isolated.

Question 4.
Try to trace the various components of human evolution (Hint: Brain size and function, skeletal structure, dietary preference, etc.)
Answer:
The various components of human evolution are as follows:

1. Brain capacity.
2. Posture
3. Food/Dietary preference and their important features.

Name brain capacity, posture and food features :

• Dryopithecus Africans : Knuckle walker, walked similar to Gorillas and Chim-panzees (was more apelike) soft fruit and leaves; canines large, arm and legs are of equal size.
• Ramapithecus: Semi-erect (more manlike) seeds, nuts canines were small while molars were large.
• Australopithecus africanus: Australopithecus africanus 450 cm3 full erect prosture, height (1 -05m) Herbivorous (ats fruits). Hunted with stone weapons, lived as trees, canines and incisors were small.
• Homo habilus: Homo habilus 735 cm3 fully erect posture, height (1 -5m) carnivo¬rous canines were small. They were first tool makers.
• Homo erectus: Homo erectus 800-1100 cm3 fully erect posture, height (1-5- l-8m) omnivorous. They used stone and bone tools for hunting games.
• Homo neanderihalensis : Homo neanderthalensis 1300 – 1600 cm3 fully erect posture, height (1-5 – l-6m) omnivorous cave dwellers, used hiles to protect their bodies and buried their dead.
• Homo sapiens fossils : Homo sapiens fossils 1650 cm3 fully erect posture with height (l -8m) omnivorous. They had strong jaw with teeth close together. They were cave dwellers, made painting and carvings in the caves. They developed a culture and were called first modem man.
• Homo sapiens sapiens : Homo sapiens sapiens 1200 – 1600 cm3 fully erect pos¬ture, height (1-5 – l-8m) omnivorous. They are the living modem men with high intelligence. They developed art, culture, language, speech, etc. They cultivated crops and domes¬ticated animals.

Question 5.
Find out through internet and popular science articles whether animals other than man has self-consciousness.
Answer:
There are many animals other than humans, which have self-consciousness. An example of an animal being self-conscious is dolphins. They are highly intelligent. They have a sense of self and, they also recognize others among themselves and others. They communicate with each other by whistles, tail-slapping, and other body movements, not dolphins, there are certain other animals such as Crow, Parrot, Chimpanzee, Gorilla, Orangutan, etc., which exhibit self-consciousness.

Question 6.
List 10 modern day animals and using the internet resources link it to a corresponding ancient fossil. Name both.
Answer:
Modern and Ancient corresponding animals :

Question 7.
Practise drawing various animals and plants.
Answer:

Question 8.
Describe one example of adaptive radiation.
Answer:
Darwin’s finches in the Galapagos Island once had a common ancestor but with evolution, they modified into different types according to their food habitat.

Question 9.
Can we call human evolution as adaptive evolution ?
Answer:
No, we can not be called human evolution as adaptive evolution.

Question 10.
Using various resources such as your school Library or the internet and discussions with your teacher, trace the evolutionary stages of any one animal, say horse.
Answer:
The evolution of horse started with Eohippus during Eocene period. It involved the following evolutionary stages :

• Gradual increase in body size
• Elongation of head and neck region
• Increase in the length of limbs and feet
• Gradual reduction of lateral digits
• Enlargement of third functional toe
• Strengthening of the back
• Development of brain and sensory organs
• Increase in the complexity of teeth for feeding on gras

• Eohippus : It had a short head and neck. It had four functional toes and a splint of 1 and 5 on each hind limb and a splint of 1 and 3 in each forelimb. The molars were short crowned that were adapted for grinding the plant diet.
• Mesohippus : It was slightly taller than Eohippus. It had three toes in each foot.
• Merychippus : It had the size of approximately 100 cm. Although it still had three toes in each foot, but it could run on one toe. The side toe did not touch the ground. The molars were adapted for chewing the grass.
• Pliohippus : It resembled the modern horse and was around 108 cm tall. It had a single functional toe with splint of 2nd and 4th in each limb.

Equus : Pliohippus gave rise to Equus or the modern horse with one toe in each foot. They have incisors for cutting grass and molars for grinding food.

Evolution Other Important Questions and Answers

Evolution Objective Type Questions

1. Choose the Correct Answer.

Question 1.
These are found at the atmosphere of earth before evolution:
(a) Water vapour, CH₄, NH₃ and Oxygen
(b) CO₂, NH₃, H₂ and Water vapour
(c) CH₄, NH₃, H₂ and Water vapour
(d) CH₄, O₃, O₂ and Water vapour.
Answer:
(c) CH₄, NH₃, H₂ and Water vapour

Question 2.
Which gas is absent at the atmosphere of earth at the time of origin of earth:
(a) NH₃
(b) H₂
(c) O₃
(d) CH₄
Answer:
(c) O₃

Question 3.
Which gaseous mixture are used and found the amino acid by Miller:
(a) Methane, Ammonia, Hydrogen and Water vapour
(b) Methane, Ammonia, Nitrogen and Water vapour
(c) Methane, Nitrogen, Hydrogen and Water vapour
(d) Ammonia, Carbon dioxide, Nitrogen and Water vapour.
Answer:
(a) Methane, Ammonia, Hydrogen and Water vapour

Question 4.
Who gave the theory “Survival of the fittest” :
(a) Charles Darwin
(b) Herbert Spencer
(c) Lamarck
(d) Hugo de Vries.
Answer:
(b) Herbert Spencer

Question 5.
Who gave the theory of inheritance of acquired, characters :
(a) Charles Darwin
(b) Lamarck
(c) Valles
(d) de Vries.
Answer:
(b) Lamarck

Question 6.
Who wrote origin of species :
(a) Oparin
(b) Beajman
(c) Lamarck
(d) Darwin.
Answer:
(d) Darwin.

Question 7.
What is the name of Darwin’s ship:
(a) Gangotri
(b) Beagle
(c) Atlantic
(d) Seagull.
Answer:
(b) Beagle

Question 8.
‘Atmosphere is a factor of variation’ who gave this theory :
(a) Mendel
(b) Darwin
(c) Lamarck
(d) Laplace.
Answer:
(c) Lamarck

Question 9.
Darwinism explain it:
(a) Characters are grown by heredity
(b) Species are changed into structural form with time .
(c) Nature selected the animals which are adapted
(d) Origin of evolution due to effect of environment.
Answer:
(c) Nature selected the animals which are adapted

Question 10.
Which antibiotic is used to Replica planting experiment of Ladderberg:
(a) Penicillin
(b) Streptomycin
(c) Erythromycin
(d) Neomycin.
Answer:
(a) Penicillin

Question 11.
Which is the basic unit of natural selection:
(a) Species
(b) Community
(c) Genous
(d) Solitary organism.
Answer:
(c) Genous

Question 12.
Who gave the theory of natural selection :
(a) Lamarck
(b) de Vries
(c) Darwin
(d) Mendel.
Answer:
(d) Mendel.

Question 13.
Darwinism is based on:
(a) Segregation
(b) Independent assortment
(c) Quantitative heredity
(d) Natural selection.
Answer:
(b) Independent assortment

Question 14.
Who discover the uses and experiment of organs:
(a) Valles
(b) Lamarck
(c) Darwin
(d) de Vries
Answer:
(a) Valles

Question 15.
The unit of natural selection :
(a) Solitary animal
(b) Family
(c) Community
(d) Species.
Answer:
(d) Species.

Question 16.
Mule is a product of:
(a) Mutation
(b) Reproduction
(c) Inter-species hybridization
(d) Intra-species hybridization
Answer:
(b) Reproduction

Question 17.
Who use first the word ‘species’:
(a) Linnaeus
(b) John
(c) Aristotle
(d) Darwin
Answer:
(b) John

Question 18.
Homologus organs are :
(a) Similar in origin
(b) Similar in function
(c) Similar in evolution
(d) Similar in behaviour.
Answer:
(a) Similar in origin

Question 19.
Which era are called as golden period of Reptilia or Dinosaurs :
(a) Mesozoic
(b) Cenozoic
(c) Palaeozoic
(d) Cenozoic.
Answer:
(a) Mesozoic

Question 20.
Dinosaurs are distinct in this era:
(a) Jurassic
(b) Triassic
(c) Cretaceous
(d) Permian.
Answer:
(c) Cretaceous

Question 21.
Vestigial organs of human’ are:
(a) Wisdom teeth, Coccyx, Nail, Eyelids, Vermiform appendix
(b) Wisdom teeth, Coccyx, Vermiform appendix, Pancreas
(c) Wisdom teeth, Coccyx, Vermiform appendix, Nictating membrane
(d) Coccyx, Wisdom teeth, Nail, Auricular muscle.
Answer:
(c) Wisdom teeth, Coccyx, Vermiform appendix, Nictating membrane

Question 22.
How made fossils :
(a) Animals are naturally buried in land after death
(b) Animals are decomposed by decomposers
(c) Animals are eaten by their hunter species
(d) Animals are destroyed due to environmental conditions.
Answer:
(d) Animals are destroyed due to environmental conditions.

Question 23.
Species which are similar in shape and different in reproduction are called :
(a) Sub-species
(b) Sibling
(c) Isotopic
(d) Allopetric species.
Answer:
(c) Isotopic

Question 24.
Name the ship which had been used by Darwin for journey :
(a) Ciloge
(b) Beagle
(c) Seagull
(d) Atlantic.
Answer:
(b) Beagle

Question 25.
Life is not in this era :
(a) Mesozoic
(b) Palaeozoic
(c) Cenozoic
(d) Azoic.
Answer:
(d) Azoic.

Question 26.
Which factor is responsible for evolution due to New-darwinism theory :
(a) Mutation
(b) Usefull variation
(c) Hybridization
(d) Mutation and Natural selection.
Answer:
(d) Mutation and Natural selection.

Question 27.
Found the age of fossils by which :
(a) By quantity of calcium ions
(b) By quantity of organic radioactive components
(c) By struggle from other mammals
(d) By structure of bones.
Answer:
(d) By structure of bones.

Question 28.
Darwin finches are related to which of the following evidences :
(a) Fossils
(b) Embryology
(c) Anatomy
(d) Geographical distribution.
Answer:
(d) Geographical distribution.

Question 29.
Who gave Recapitulation theory :
(a)Weizmann
(b) Haeckel
(c) Darwin
(d) Malthus.
Answer:
(b) Haeckel

Question 30.
Which definition of organic evolution is correct:
(a) Evolutionary history of a species
(b) History of species with the variations is the species
(c) Embryonal history of species
(d) Development of species.
Answer:
(a) Evolutionary history of a species

Question 31.
What is the perfect sequence of development of human:
(a) Peking man, Heidelberg man, Neanderthal Cro-Magnon
(b) Peking man, Homo sapiens, Cro-Magnon, Neanderthal
(c) Peking man, Neanderthal,.Homo sapiens, Heidelberg
(d) Peking man, Cro-Magnon, Homo sapiens, Neanderthal.
Answer:
(a) Peking man, Heidelberg man, Neanderthal Cro-Magnon

Question 32.
Which of the following is the most primitive ancestor of man :
(a.) Australopithecus
(b) Ramapithecus
(c) Homo habilis
(d) Homo neanderthalensis.
Answer:
(b) Ramapithecus

Question 33.
Ancestral amphibians were tetrapods that evolved during :
(a) Jurassic period
(b) Cretaceous period
(c) Devonian period
(d) Carboniferous period.
Answer:
(c) Devonian period

2. Fill in the Blanks :

1. Earth is a member of …………….
2. ……………. wrote ‘Origin of life’.
3. Oxygen is find the earth because photo-synthetic organisms are present on the earth, this phenomenon is called …………….
4. ………….. is the connecting link between Reptiles and Aves.
5. …………………. is the ancesters of horse.
6. The evolution of ……………. molecule set the stage for evolution of autotrophs.
7. Evolution of birds and mammals were ……………. era.
8. Golden era of Dinosaurs is ……………. period.
9. ……………. fossil man has been known from Shivalik hills in India.
10. Book of Charles Darwin “Origin of life” has been explained of …………….
11. ……………. be change of hareditary characters.

Answer:

1. Solar system
2. Oparin
3. Oxygen revolution
4. Archaeopteryx
5. Eohippus
6. Chlorophyll
7. Jurassic
8. Mesozoic
9. Ramapithecus
10. Natural selection
11. Mutation.

Question 3.
Match the Following :

Answer:

1. (d)
2. (a)
3. (e)
4. (c)
5. (b)

Answer:

1. (d)
2. (c)
3. (e)
4. (a)
5. (b)
6. (f).

4. Answer in One Word / Sentence:

1. The matter which gave rise to the universe 15 billion years ago.
2. The matter which is a link between acellular and cellular system.
3. The island at which Darwjn studies the organisms for his theory of evolution.
4. Origin of two or more unlike species from a common ancestor.
5. The whole process of development at changes from embryo to adult organism.
6. The process of changes in the course of origin of a new species.
7. The theory of organic evolution proposed by Darwin.
8. The permanent, heritable and spontaneous changes in organisms.
9. The remains of ancient organisms.
10. The organs which are different in their origin but have similar function.

Answer:

1. Ylem
2. Coacervates
3. Galopegos
4. Adaptive radiation
5. Ontogeny
6. Phytogeny
7. Natural selection
8. Mutation
9. Fossils
10. Homologous organs.

Evolution Very Short Answer Type Questions

Question 1.
Name the non-cellular organism.
Answer:
Virus.

Question 2.
Name the theory which tell about the milky way and formation of star.
Answer:
Big Bang.

Question 3.
Releasing of 02 by the evolution of photosynthesis an ancient time is called?
Answer:
Oxygen revolution.

Question 4.
Which planet has the possibility of origin of life other than earth?
Answer:
ars.

Question 5.
Where did life originate ?
Answer:
In water.

Question 6.
What is the art of limitation, which is practiced the world over from annoying siblings or plant resembles another creature to gain other advantages?
Answer:
Mimicry.

Question 7.
Name the method of the changing of the structure of a gene resulting in a variant form that may be transmitted to.
Answer:
Mutation.

Question 8.
What is the collection of different genes within an inter breading population?
Answer:
Gene pool.

Question 9.
Who wrote origin of species?
Answer:
Charles Darwin.

Question 10.
Who proposed the theory of natural selection?
Answer:
Darwin.

Question 11.
Who proposed the Recapitulation theory or Biogenetic law?
Answer:
Haeckel.

Question 12.
Astronomical distance measured in?
Answer:
Astronomical distance measured in Light years.

Question 13.
Name the theory by which earth is said to originate.
Answer:
The big bang theory.

Question 14.
What is fossil ?
Answer:
Fossils are the remains or impressions of ancient organisms preserved in sedimentary rocks or other media.

Question 15.
What is mutation ?
Answer:
New species originate due to changes of hereditary characters are called mutation.

Question 16.
Name the scientist who tell the spontaneous theory is wrong.
Answer:
Louis Pasteur’s.

Question 17.
Which era is called golden period of Dinosaurs?
Answer:
Mesozoic period is called golden period of Dinosaurs.

Question 18.
In which ship Darwin studied the nature ?
Answer:
Beagle.

Question 19.
Name any two vertibrates body organ which are homologus organs of human forelimb.
Answer:
(1) Flipper of Whale,
(2) Wing of birds.

Question 20.
What is the scientific name of modern man ?
Answer:
Homo sapiens.

Question 21.
Who is the early man of the modern human?
Answer:
Cro-Magnon peoples are early human of modern human.

Question 22.
Who are the early human and sub-human.
Answer:
Ramapithecus is early human and Australopithecus is early human.

Question 23.
Which human form first started to walk on two legs?
Answer:
Australopithecus form first started to walk on two legs.

Question 24.
Which type of human was ‘Cro-Magnon’ on the basis of food in take?
Answer:
Cro-Magnon was carnivorous.

Question 25.
On the basis of evolution which human had brain size of 1400cc?
Answer:
Neanderthal.

Question 26.
Give the name of apelike ancestors of humans
Answer:
Apelike ancestors of human’s are Dryopithecus.

Question 27.
Differentiate between Dryopithecus and Ramapithecus.
Answer:
Dryopithecus were apelike but Ramapithecus were mostly human like.

Evolution Short Answer Type Questions

Question 1.
What is virus ? Why is it treated as a link between living and non-living ?
Answer:
Viruses are simplest organism of the earth, which consists of nucleic acid (DNA or RNA) surrounded by protein cover. It shows characteristics of living as well as non-living organisms.
(A) Living characters of virus:

• Virus shows structural differentiations.
• They contain hereditary material.
• They exhibit mutation.
• They spread plant and animal diseases.
• Growth and development present.
• They exhibit adaptaion.
• They possess sensitivity.

(B) Non-living characters of virus:

• Lack protoplasm and cell organelles.
• Can be crystallized.
• No metabolic activities seen.
• Cannot reproduce outside living cells.
• They lack enzymes.

Due to above reason, viruses are considered as link between living and non-living organisms, thus, it is the first life originated in the earth.

Question 2.
What is oxygen revolution? Explain.
Answer:
Oxygen revolution : Evolution of 02 in photosynthesis during primitive environmental conditions is very important because, it is required in the evolution of organism and conversion of reducing environment into oxidizing environment hence, it is called oxygen revolutioa Oxygen evolution should cause the following changes in the environment:

• Oxygen evolution should cause the conversion of reducing environment into oxidizing environment
• Ozone layer is formed 15 miles above from the earth which absorbs the ultraviolet light of the sunlight and thus, prevents the entry of uv light in the atmosphere.
• O₂ present in the environment dissociates methane (CH₄) into CO₂ and O₂. This CO₂ is used in photosynthesis.
• NH₃ of the primitive environment is dissociated into H₂O.and nitrogen.
  CH₄ + 2O₂2 → CO₂ + 2H₂O
  4NH₃ + 3O₂ → 2N₂ + 6H₂O.

Question 3.
Explain the origin of the earth.
Answer:
Origin of the earth:

• Earth was formed 4-5 billion years back.
• Initially, die surface was covered with water vapOur, methane, C02 and NH3.
• The UV rays of the sun broke water into hydrogen and oxygen.
• Hydrogen escaped and oxygen combined with NH3 and CH4 to form water, C02 and other gases, also forming die ozone layer.
• Cooling of water vapour led to rain which filled the depressions on earth’s surface, forming water bodies.

Question 4.
Mention the names of discoveries and principles given by the following scientists:

1. Louis Pasteur
2. A. I. Oparin
3. Urey and Miller
4. Francesco Redi
5. Faux.

Answer:

1. Louis Pasteur : He proved that air contains spores of microorganism and Biogenesis theory was supported by him.
2. A. I. Oparin: He presented the biochemical explanation of origin of life in his book “The Origin of Life on Earth”.
3. Urey and Miller : They supported the evidence of Oparin-Haldane theory of Origin of life.
4. Francesco Redi: He by conducting experiments proved that abiogenesis cannot exist but bioginesis theory can exist i.e., Life arises from pre-existing life.
5. Faux: He has been experimentally supporting the organic substances as described by Oparin.

Question 5.
Write down the difference between :

1. Ozone and Oxygen
2. Micro-molecules and Macro-molecules.

Answer:
1. Differences between Ozone and Oxygen :

2. Differences between Micro-molecules and Macro-molecules :

Question 6.
What are homologous organs ?
Or
What is homology ?
Answer:
Organs which are similar in structure and origin but different in appearance and functions are called homologous organs and the phenomenon is called homology.
Examples : Forelimbs of bat, wings of bat, hands of man, forelimbs of horse. These are the examples of homologous organs because, they are made up of similar bones, hu¬merus, radius-ulna, carpals, metacarpals and fingers.

Question 7.
What do you mean by analogous ?
Answer:
Analogous organs: Organs which are different in origin and structure but per¬forming similar functions are known as analogous organs and the phenomenon is called as analogy. Analogous organs do not indicate phylogeny.
Examples : Wings of butterflies are made up of chitin, wings of birds made by production of feathers on forelimbs and skin present between the fingers of bat are the examples of analogous organs.

Question 8.
What is the difference between homologous and analogous organs ? Give two examples of each of them.
Answer:
Differences between Homologous and Analogous organs :

Question 9.
What do you mean by vestigial organs ?
Or
Write the two names of vestigial organs of man.
Or
What are vestigial organs ? Explain. Write four vestigial organs of the human body.
Answer:
Vestigial organs : Organs that are reduced and have become functionless in an organism but were functional in their ancestors are called as vestigial organs :
Examples :

• Vermiform appendix
• Coccygial vertebrae
• Nictitating membrane in the eyes of human
• Muscles of external ear (Pinna).

Question 10.
What is connecting link ? Also explain the significance of connecting links.
Answer:
Connecting link : Certain organisms which share characters with two different groups. Such organisms are called connecting links.
Examples : Some fossils present in nature like Archaeopteryx is known as fossils connecting link and it is the connecting link of birds and reptiles. Neopilina, Platyptus, Protopterus, etc. Neopilina is a mollusc and is the connecting link of mollusca and annelida.
Significance of Connecting links : It proves the process of organic evolution and helps in the identification of organism closely related.

Question 11.
Write down the demerits of Darwinism.
Answer:
Some of the demerits of Darwinism are :

• Darwinism stresses upon small fluctuating variations which has no role in evolution.
• Does not satisfactorily explain effect of use and disused and presence of vestigial organs:
• It did not differentiate somatic and germinal variations.
• It explains survival of the fittest but not arrival of the fittest. .

Question 12.
Differentiate between Lamarckism and Darwinism.
Answer:
Differences between Lamarckism and Darwinism:

Question 13.
Explain Lamarckism in short
Or
Explain Lamarckism of organic evolution in brief.
A ns. Lamarckism : In 1809, Lamarck has proposed a theory to explain organic evolution, which is known, as the “Theory of inheritance of acquired characters.” According to Lamarck, organisms acquire certain characters during their lifetime due to changes in environment and these acquired characters are heritable. According to this theory, new species are originated as follows :

• New requirements and wills are produced in the organisms due to the effect of changed environment
• New requirements and wills of organisms resulting in the production of new habits.
• Changes in the habit bringing about modifications of the organ.
• New habits resulting in the use or disuse of the organs:
• Use of organ resulting in the development of acquired characters.
• These acquired characters are heritable.
• Inheritance of acquired characters resulting in the development of new species.

Evolution Long Answer Type Questions

Question 1.
Draw a well-labelled diagram of Miller and Urey’s experiment
Answer:

Experimental evidence of Chemical evolution or Miller’s experiment:

• Experiment was performed by S.L. Miller and H.C. Urey in 1953.
• Experimental set-up: In a closed flask containing CH4, H2, NH3 and water vapoiy at 800°C, electric discharge was create. The conditions were similar to those in primitfve atmosphere.
• Observations: After a week, they observed presence of amino acids and complex molecules like sugars, nitrogen bases, pigments and fats in the flask.
• Conclusions : (i) It provides experimental evidence for the theory of chemical origin.
  (ii) It showed that the first non-cellular form of life was created about 3 billion years ago.
  (iii) It showed that non-cellular biomolecules exist in the form of DNA, RNA, polysaccharides and protein.

Question 2.
Write an essay on modern concepts of origin of life.
Or
Explain the role of non-living in origin of life.
Answer:
Modern concept of origin of life : The modem concept of origin of life was postulated by a Russian biochemist A.I. Oparin in 1936. According to this theory, after the formation of earth various chemicals played important role in the formation of atmosphere. Life originated and first organism came into existence from certain molecules when atmospheric conditions became suitable. According to Oparin, life originated in the following steps:

1. Formation of earth and its atmosphere: Earth is believed to be originated some 4,500 million years ago by the condensation and cooling of the clouds of cosmic dust and gases called ylem. The heavier elements collected at the core and lighter elements around the core. Outermost layer contains H, C, O and N. Oxygen was found only in combination of other elements. These four elements reacted with each other forming H₂, H₂O, CH₄, NH₃, CO₂ and HCN.

2. Formation of small organic molecules : The mixture of methane, ammonia, water and hydrogen comes in contact of solar energy. Cosmic rays and electric discharge could produce some simple organic compounds. These simple organic compounds formed in such a way and accumulated in primitive atmosphere and oceans were responsible for synthesis of complex micro molecules as follows :

3. Formation of polymers : It is clearly understood from the above description that a large number of micro molecules such as hydrocarbons, amino acids, fatty acids, purine and pyrimidines and simple sugars accumulated in the oceans. When atmospheric water condensed on further cooling, the inorganic precursors collided, reacted and aggregated to form new molecules of increasing size and complexity. Thus, by polymerization macromolecules were formed. The chemical reactions for the formation of macro-molecules can be summarized as follows:

(a) Sugar + Sugar → Polysaccharides
(b) Fatty acid + Glycerine → Lipids
(c) Amino acid + Amino acid → Protein
(d) Nitrogenous base (Adenine) + Sugar + Phosphate → Adenosine phosphate
(e) Nitrogenous base + Sugar → Nucleoside
(f) Nucleoside + Phosphate → Nucleotide
(g) Nucleotide + Nucleotide → Nucleic acid.

4. Formation of molecular aggregates and primitive cells : Over a vast of time, these molecules became associated with one temporary complex. Ultimately, it leads to the formation of a coacervate. A coacervate is a solution of high molecular weight of chemicals, i.e., proteins and carbohydrates, which become bounded by lipid membrane, which is selectively permeable. The coacervate grows by absorbing molecules from their environment. The substances which got accumulated in the coacervates underwent reactions and resulted in the molecular reorganization of some proteins into enzymes. A coacervate having nucleoprotein surrounded by various nutritive organic substances and covered by surface membrane is considered to be the precell, which got later transformed into first living cell. The coacervate can reproduce by budding.

5. Evolution of complex biochemical reactions : Primitive organism utilize chemi¬cal substances present in the environment as food hence, they are:

(a) Heterotrophic, chemosynthetic organisms appeared due to mutation and natural selection in heterotrophs.
(b) Blue-green algae evolved from chemosynthetic organisms by mutation and natural selection.
(c) The liberation of free oxygen into the atmosphere produced by the blue-green algae due to the process of photosynthesis. It finally changed the reducing atmosphere into an oxidizing one and therefore, all possibilities of further chemical evolution were finished.
Free living eukaryotes originated in the ocean from blue-green algae.

6. The origin of well-developed organisms : From the simple eukaryotes which were like unicellular organisms of today various forms of life evolved during passage of time.

Question 3.
Write the process of formation of organic molecules in sea water on earth with the help of Miller and Urey’s experiment
Answer:
The work of A.I. Oparin (1938-1965), HLUrey and Stanley Miller (1959) pro¬vided evidences in the favour of biochemical origin of life. They had prepared the atmos¬phere like that of primitive earth and as described by Oparin, they made the synthesis of organic compounds by the following methods:

(i) Four elements H, C, O (not free O₂) and N react .with each other to form H₂O, CH₄, NH₃, CO₂ and HCN on primitive earth.

(ii) From these four elements following organic molecules were formed in sea water of earth:
(a)

(b) CH₄, H₂O, NH₃ → Amino acids.
(c) CH₄, HCN, H₂O, NH₃ → Nitrogenous bases.

(iii) Macro-molecules of organic compounds were synthesized by these above pre¬pared organic compounds.

(a) Sugar + Sugar → Polysaccharides (Carbohydrate).
(b) Fatty acids + Glycerol → Fats.
(c) Amino acid + Amino acid → Protein.
(d) Nitrogenous base + Sugar → Nucleoside.
(e) Nucleoside + Phosphoric acid → Nucleotide.
(f) Nucleotide + nucleotide → Nucleic acid.
(g) Nitrogenous base (Adenine) + Sugar + Phosphate →Adenosine phosphate.
(iv) The above organic compounds and salts together constituted the first living being.

Question 4.
Name connecting link of reptiles and birds. Also write their characters.
Answer:
Archaeopteryx is the connecting link of birds and reptiles. Archaeopteryx was a bird. It is regarded as the connecting link between reptiles and birds, which suggests the path of evolution of the latter from the former. It is found as fossils. They are found during Jurassic period 140 million years. Archaeopteryx exhibits both reptiles and birds like characters.

1. Reptiles like characters:

• Bones were similar to that of reptiles in which air sacs were absent.
• Tail bearing vertebra.
• It had teeth in jaws, scales were present on the body.
• Metacarpals were free.
• Pelvic girdle recombines with the pelvic girdle of reptiles.

2. Birds like characters :

• Presence of feathers on body. .
• Forelimbs were modified in wings.
• Skull large and monocondylar.
• Jaws were modified into beak.
• Hallux was backwarded and pointed.

Question 5.
Give a detailed account of theory of natural selection.
Or
Describe the Darwin’s opinion about the origin of new species of organisms.
Answer:
Charles Darwin (1809-1882) explained the theory of evolution in his book “Origin of species by natural selection.” Darwin undertook a long voyage for five years in the capacity of a naturalist on a British warship ‘Beagle’. He travelled to islands of Galapagos and collected evidences to explain evolution.
To explain origin of species he gave theory of natural selection as a mechanism for evolution.

The main points of Darwinism are given below:

1. Over production of offsprings : Every living being has an inherent tendency to produce more offspring than that can survive.

2. Struggle for existence : Though the offsprings are produced in large number yet their production remain almost constant. This is because of struggle for existence. There is struggle for food, space, breeding, etc. Moreover death of individuals due to diseases an

3. Survival of the fittest: Darwin believed that any individual is successful in struggle for existence if it survives long enough to produces offsprings. Individuals who are fit in a particular environment can only survive.

4. Variation: Due to constant struggle, the organisms change themselves in accordance with the new needs.

5. Natural selection : In the struggle, for existence organisms having variations favourable to the environment would have more chance to survive and reproduce their own kind. Those which do not possess favourable variations would die or fail to reproduce.

6. Origin of species : Any changes in environmental conditions cause natural selection to act upon the population and select the well adapted individuals. It results in changes of characters of the populations. By the inheritance of these changes in successive generations, new species are formed.

Question 6.
Organic Evolution is a continued process, explain it in favour of it giving any three evidences.
Answer:

Evolution is a complex phenomenon accounting for the present day diversity among organisms. But it has clearly maintained the basic unity among them since it occurred over a period of millions of years, no one would have seen/recorded evolution and hence scientists have provided various evidences to prove evolution.

Some of the evidences of organic evolution are described below :

I. Evidences from Embryology :

• Important activities that occur various animals are:
• For the survival, all animals get energy and various substances from environment.
• In all organisms energy is produced from ATP.
• In all organisms, the duplication of DNA is similar.
• In all organisms, protein synthesis is same and it is produced from ribosomes.
• In all organisms respiration and steps of respiration is same.
• All organisms multiplicate and reproduce, due to which they have basic similarities.
• All organisms conduct hereditary characters on similar principles.

II. Evidence from Anatomy: Anatomy of living organisms will be explained with different examples:

• Homologous organs: Organs which are similar in structure and origin but diffeifent in function and appearance is known as homologous organs.
• Analogous organs : Organs which are different in origin and structure but performing similar functions are known as analogous organs.
• Vestigial organs : Organs that are reduced and have become functionless in an organism, but were functional in their ancestors are called vestigial organ.

III. Evidences from vestigial organs: Organs of the body which are non-functional but they are functional in some other organisms are called vestigial organs:

Morphological evidence of evolution is provided by the presence of vestigial organs of body which are often undesired, degenerated and non-functional. These might have been large and functional in some other animals or in ancestors of those which now possess it in rudimentary forms. e.g„ vermiform appendix in man, muscles of external ear (pinna) in man, nictitating membrane or plica, semilunaris in human eye, wisdom teeth (third pair of molars) tail bone (coccyx) in man, wings of ostrich, hindlimbs in snakes, etc.

Question 7.
What do you mean by organic evolution? How do fossils exhibit evidence to prove organic evolution?
Answer:
Descent with modification in organism is known as organic evolution.

Evidences of organic evolution from fossils record : Fossils are treated as significant evidence of organic evolution. Fossils are the remains or impressions of ancient organisms preserved in the layers of rock and soil. Fossils only do not prove the theory of organic evolution, yet it evidently prove that gradually complexity increased in body organization. The complexity in the body of organization can be noticed as we study the upper layers. Thus, it can be concluded from above observations :

• The crust of the earth and the organisms living on it underwent change in the course of time.
• The organisms with simple structural organization originated earlier than the complex ones.
• Some of the organisms lived on the earth for short time and became extinct. This was a result of drastic changes in the climate on the earth.

Hence, forth fossils produce bonafide record of such plants and animals which had shown their existence once upon a time and now are extinct or not present exactly in the same form, thus, producing strong evidence in favour of organic evolution.

MP Board Class 12th Biology Solutions

MP Board Class 12th Biology Solutions Chapter 14 Ecosystem

Ecosystem NCERT Text Book Questions and Answers

Question 1.
Fill in the Blanks:

1. Plants are called as …………….. because they fix carbon dioxide.
2. In an ecosystem dominated by trees, the pyramid (of numbers) is ………………… type.
3. In aquatic ecosystem, the limiting factor for the productivity is …………………….
4. Common detritivores in our ecosystem are ………………………..
5. The major reservoir of carbon on earth is ………………………
Answer:

1. Producer
2. Inverted
3. Light
4. Earthworm
5. Ocean and Biosphere.

Question 2.
Which one of the following has the largest population in the food chain:
(a) Producers
(b) Primary consumers
(c) Secondary consumers
(d) Decomposers.
Answer:
(d) Decomposers.

Question 3.
The second trophic level in a lake is:
(a) Phytoplankton
(b) Zooplankton
(c) Benthos
(d) Fishes.
Answer:
(b) Zooplankton

Question 4.
Secondary producers are:
(a) Herbivors
(b) Producers
(c) Carnivors
(d) None of the above.
Answer:
(a) Herbivors

Question 5.
What is the percentage of photosynthetically active radiation (PAR) in the incident solar radiation:
(a) 100%
(b) 50%
(c) 1-5%
(d)2 -10%.
Answer:
(b) 50%

Question 6.
Distinguish between:
(a) Grazing food chain and detritus food chain
(b) Production and decomposition
(c) Upright and inverted pyramid
(d) Food chain and Food web
(e) Litter and Detritus
(f) Primary and Secondary productivity.
Answer:
(a) Grazing food chain and detritus food chain

(b) Production and decomposition

(c) Upright and inverted pyramid

(d) Food chain and Food web

(e) Litter and Detritus

(f) Primary and Secondary productivity.

Question 7.
Describe the components of an ecocystem.
Answer:
Ecosystem: The system resulting from the interaction between organisms and their environment is called as ecosystem.

(a) Producers: Organism, which can synthesize their own food are included under producers, e.g., Volvox, Pandorina, Oedogonium, Saggitaria, Utricularia, Azolla, Trapa, Lemna, Typha, Nymphaea etc. form the producer class of the pond ecosystem.

(b) Consumers:

• Primary consumer: Animals, which feed on producers are included into this category e.g., Daphnia, Cyclops, Paramoecium, Amoeba and small fishes.
• Secondary consumers: Primary consumers also serve as food for water sn’akdls, a few tortoise, few types of fish etc. hence, these are carnivores.
• Tertiary consumers: Secondary consumers also serve as food for aquatic birds like kingfisher, cranes, big fish and these together form a top class carnivorous group and called as tertiary consumers.

(c) Decomposers: All producers and consumers die and accumulate on the floor of the pond. Even the waste material and faeces of these animals get accumulated on the floor of the pond. Similarly, the floor of pond is also occupied by decomposers, which include bacteria and fungi. These decomposers decompose complex organic compounds of then- bodies into simpler forms which are finally mixed with soil of floor of ponds. These are again absorbed by the roots of producer plants and thus matter is recycled.

Question 8.
Define ecological pyramids and descirbe with examples, pyramids of number and biomass.
Answer:
Ecological Pyramid : The relation between producers and consumers in a ecosystem can be graphically represented in the form of a pyramid called ecological pyramid. The base always represent the producers or the first trophic level and the apex represents top level consumer or the lost trophic level ecological pyramids are of three types :

1. Pyramid of number
2. Pyramid of biomass
3. Pyramid of energy.

The biomass, i.e., the living weight of the organisms in the food-chain present at different trophic levels in an ecosystem forms the pyramid of biomass.

When biomass of consumers is greater than biomass of producer then pyramid is called as inverted pyramid of biomass.eg., pyramid of biomass of pond ecosysyem is always inverted.

Ecosystem: The system resulting from the interaction between organisms and the environment is called as ecosystem.

Question 9.
What is primary productivity ? Give brief description of factors that affect primary productivity.
Answer:
The rate of biomass production is called productivity.
It is expressed in terms of g^-2yr^-1  or(Kcal-m^-2) yr^-1 to compare the productivity of ecosystems.
It can be divided into Gross Primary Productivity (GPP) and Net Primary Productivity (NFP).

Gross Primary Productivity of an ecosystem is the rate of production of organic matter during photosynthesis. A considerable amount of GPP is utilized by plants in respiration.

Gross primary productivity minus respiration losses (R), is the Net Primary Productivity (NPP). GPP – R=NPP.
Primary productivity depends on :

• The plant species inhabiting a particular area.
• The environmental factors.
• Availability of nutrients.
• Photosynthetic capacity of plants.

Question 10.
Define decomposition and describe the processes and products of decomposition.
Answer:
Decomposition is the process that involves the breakdown of complex organic matter or biomass from the body of dead plants and animals with the help of decomposers into inorganic raw materials such as carbon dioxide, water, and other nutrients.
The various processes involved in decomposition are as follows:
1. Fragmentation: It is the first step in the process of decomposition. It involves the breakdown of detritus into smaller pieces by the action of detritivores such as earthworms.

2. Leaching: It is a process where the water soluble nutrients go down into the soil layers and get locked as unavailable salts.

3. Catabolism: It is a process in which bacteria and fungi degrade detritus through various enzymes into smaller pieces.

4. Humification: The next step is humification which leads to the formation of a dark coloured colloidal substance called humus, which acts as reservoir of nutrients for plants.

5. Mineralization: The humus is further degraded by the action of microbes, which finally leads to the release of inorganic nutrients into the soil. This process of releasing inorganic nutrients from the humus is known as mineralization. Decomposition produces a dark coloured, nutrient-rich substance called humus. Humus finally degrades and releases inorganic raw materials such as CO₂, water, and other nutrient in the soil.

Question 11.
Given account of Explain energy flow in ecosystem.
Answer:
Energy flow: In die ecosystem, energy is transferred in an orderly sequence. The flow of solar energy from producers to consumers and to decomposers subsequently in an ecosystem is known as energy flow. Energy flow is an ecosystem is always unidirectional. Sun is the sole source of solar energy in an ecosystem. Green plants utilize this energy in photosynthesis and convert it in the form of chemical energy and store it. Plants utilize maximum part of this energy to do its biological functions. Some of it is converted into heat and released in the environment. Remaining part of the energy is stored in various components of the body.

When a consumer eats these producer plants, the energy is then transferred into its body. In any food-chain energy flows from primary producers to primary consumers, from primary consumers to secondary consumers and secondary consumers to tertiary consumers and so on. Because every organism of a trophic level continuously converts chemical energy into heat, there is always a loss of energy with each step in a food-chain. According to an estimate only 10% of the total energy obtained is transferred from one trophic level to another.

Question 12.
Write important features of a sedimentary cycle in an ecosystem.
Answer:
Sedimentary cycles have their reservoirs in the earth’s crust or rocks. Nutrient elements are found in the sediments of the earth. Elements such as sulphur, phosphorus, potassium, and calcium have sedimentary cycles.

Sedimentary cycles are very slow. They take a long time to complete their circulation and are considered as less perfect cycles. This is because during recycling, nutrient elements may get locked in the reservoir pool, thereby taking a very long time to come out and continue circulation. Thus, it usually goes out of circulation for a long time.

Question 13.
Outline salient features of carbon cycling in an eosystem.
Answer:
Carbon constitutes 49 percent of dry weight Of an organisms.

• 71 percent of the carbon is found dissolved in oceans which is responsible for its regulations in atmosphere.
• The carbon cycle occurs through atmosphere, oceans and through living and dead organisms.
• It is estimated that 4xl013 kg of Carbon is fixed in the biosphere through photosynthesis annually.
• Carbon is returned to atmosphere as CO₂ by animals and plants through respiration and the activities of decomposers.
• Some amount of fixed carbon is lost as sediments and removed from circulation.
• Burning of wood, forest fire, volcanic activity and combustion of organicjnatter and fossil fuels are some essential sources for releasing CO₂ in the atmosphere.
• Human activities like deforestation and vehicular burning or fossil fuels has caused in increase in the amount of CO₂ in atmosphere.

Ecosystem Other Important Questions and Answers

Ecosystem Objective Type Questions

Choose the Correct Answer

Question 1.
Position of man in food chain of all ecosystem is as :
(a) Consumer
(b) Producer
(c) Producer and consumer
(d) Decomposer.
Answer:
(a) Consumer

Question 2.
Flow of energy in an ecosystem is :
(a) Unidirectional
(b) Bi-directional
(c) Three directional
(d) Quadri-directional.
Answer:
(a) Unidirectional

Question 3.
The word “ Ecosystem” was first used by :
(a) Tansley
(b) Odum
(c)Writier
(d) Mishra and Puri.
Answer:
(a) Tansley

Question 4.
Source of energy in an ecosystem is:
(a) Solar energy
(b) Green plants
(c) Food substances
(d) All of the above.
Answer:
(a) Solar energy

Question 5.
Pyramid of number of trees in an ecosystem is always:
(a) Inverted
(b) Upward
(c) Both (a) and (b)
(d) None of these.
Answer:
(a) Inverted

Question 6.
Correct food chain is:
(a) Grass → Grasshopper → Frog Snake → Hawk
(b) Grass → Frog → Snake → Peacock
(c) Grass → Peacock → Grasshopper → Hawk
(d) Grass → Snake → Rabbit.
Answer:
(a) Grass → Grasshopper → Frog Snake → Hawk

Question 7.
Pyramid of biomass of an ecosystem of lake is:
(a) Upward
(b) Inverted
(c) Inverted and Upward both
(d) None of these.
Answer:
(b) Inverted

Question 8.
Man is:
(a) Producer
(b) Carnivore
(c) Herbivore
(d) Omnivorus.
Answer:
(d) Omnivorus.

Question 9.
Decomposer are:
(a) Rats
(b) Algae
(c) Bacteria and Fungi
(d) Goats.
Answer:
(c) Bacteria and Fungi

Question 10.
Man made ecosystem is:
(a) Pond
(b) Aquarium
(c) Forest
(d) Lake.
Answer:
(b) Aquarium

Question 11.
Pyramid of energy is a forest ecosystem is:
(a) Always Inverted
(b) Always upward
(c) First upward than Inverted
(d) None of the above.
Answer:
(b) Always upward

Question 12.
Study of ecosystem of species is called:
(a) Ecology
(b) Autecology
(c) Synecology
(d) None of these.
Answer:
(b) Autecology

Question 13.
Food chain starts from:
(a) Respiration
(b) Photosynthesis
(c) Decomposition
(d) Nitrogen fixation.
Answer:
(b) Photosynthesis

Question 14.
Flow of energy and food in a food web is:
(a) Unidirectional
(b) B i-directional
(c) Multidirectional
(d) None of these.
Answer:
(c) Multidirectional

Fill in the Blanks:

1. The transitional zone between two adjacent communities is called ………………………
2 The term ecosystem was proposed for the first time by ………………………..
3. The brief source of energy in ecosystem is …………………….
4. Bacteria which fix the nitrogen is called ……………………
5. All ecosystem are dependent of energy on …………………….
6. Balance of ecosystem is called ………………………
7. Pyramid of energy is always …………………………
8. All the plant of a particular geographic area constitute ………………………. of the place.
Answer:

1. Ecotone,
2. Tansley,
3. Sunlight,
4. Rhizobuim,
5. Solar energy,
6. Ecological balance,
7. Upright,
8. Flora.

3. Match the Following:


Answer:

1. (b)
2. (e)
3. (d)
4. (a)
5. (c).

Answer:

1. (b)
2. (e)
3. (d)
4. (a)
5. (c)

Question 4.
Answer in One Word/Sentence:

1. Mention the two name of biotic components of ecosystem.
2. Who proposed the term ecosystem?
3. Which ecosystem is more stable?
4. Name the relatively loss stable ecosystem.
5. Name the ecosystem showing maximum stratification.
6. Give two examples of artificial ecosystem.
7. Give the name of any two food chains.
8. Write the name of basic unit of ecology.
9. Name the organisms found on the surface of water bodies.
10. Name the transitional zone of two adjacent communities.
11. Name the process of establishment of organisms is any new area.
12. From where xerosere started?
13. Who has proposed the term succession?
14. Name the succession started from naked rock. ‘

Answer:

1. Biotic, Aboitic
2. Tansley
3. Ocean
4. Desert
5. Aquatic
6. Aquarium, crop¬land
7. Grazing, Detritus
8. Producer
9. Benthos
10. Ecotone
11. Succession
12. Rocks
13. Hult(1885)
14. Lithosere.

Ecosystem Very Short Answer Type Questions

Question 1.
Name the process of soil formation.
Answer:
Pedogenesis.

Question 2.
What is the orientation of pyramid of energy?
Answer:
Upright.

Question 3.
Which ecosystem is most established?
Answer:
Complex ecosystem.

Question 4.
When many food chain operate simultaneously and interlock such pattern is formed.
Answer:
Food web.

Question 5.
Name the ecosystem which shows most productivity.
Answer:
Tropical ecology.

Question 6.
What are fungi and bacteria called in an ecosystem?
Answer:
Micro consumer or Decomposer.

Question 7.
Which part of the energy is transferred from one trophic level to other in ecosystem?
Answer:
10 %.

Question 8.
Name the type of chemosynthetic bacteria.
Answer:
Autotrophic.

Question 9.
Name the word which is similar to ecosystem given by Pro. R. Mishra.
Answer:
Ecocosm.

Question 10.
Name the trophic level in which green plants are found.
Answer:
Primary trophic level.

Question 11.
Who gave the word transformer for producer?
Answer:
By E. J. kormondy.

Question 12.
Name any two sedimentary cycle.
Answer:

1. Phosphorus cycle
2. Sulpher cycle.

Question 13.
The energy pyramids are always.
Answer:
Upright.

Question 14.
Give examples of decomposers.
Answer:
Bacteria and Fungi.

Question 15.
Who gave 10% rule of energy?
Answer:
Lindeman.

Question 16.
Which form of nitrogen is absorbed by plants?
Answer:
In the form of nitrate ion (No₃^–).

Question 17.
Name two types of food chain.
Answer:

1. Grazing food chain,
2. Detritus food chain.

Ecosystem Short Answer Type Questions

Question 1.
Differentiate between food chain and food web.
Answer:

Question 2.
Write the names of important components of atmosphere.
Answer:
(A) Abiotic components:

• Energy: Light, temperature, energy of chemical substances.
• Materials: Water, soil, salts etc.

(B) Biotic components:

• Producers: e.g., green plants.
• Consumers: Primary, secondary and tertiary.
• Decomposers: Bacteria, fungi.

Question 3.
Write the name and ratio of different components of biosphere.
Answer:
Name and ratio of different components of biosphere is :

Some gases are also found in biosphere e.g., Helium, Neyon and Crypton are found in less quantity.

Question 4.
Differentiate between detritivore and decomposer.
Answer:
Detritivore are organisms which feed on detritus and break them into smaller particles, e.g., earth worm. And decomposer are organisms which by secreting enzyme’s break down complex organic matter into in organic substance e.g. some bacteria and fungi.

Question 5.
Explain consumers of ecosystems.
Answer:

1. Producers: All the green plants.
2. Consumers: Depends on others for food.
   (i) Primary consumer: Depends on plants called herbivores.
   (ii) Secondary consumers: Depends on herbivores for food.
   (iii) Tertiary consumers: Depends on secondary consumers.
3. Decomposers: They decomposed dead organic matter.

Question 6.
Differentiate between biome and ecosystem.
Answer:
An ecosystem is the interaction of living and non-living things in an environment. A biome is a specific geographic area notable for the species living there.

Question 7.
Draw a pyramid of energy of grass land in ecosystem.
Answer:

Question 8.
Explain nitrogen cycle in nature.
Answer:

Question 9.
Explain sulphur cycle by diagram.
Answer:

Question 10.
Explain the effect of light on plants.
Answer:
Effect of light on plants: Light is the source of energy. It is essential for life. It is an important factor of an ecosystem. The existence of life on earth is because of light obtained from sun. Sunlight is essential for photosynthesis, help in preparation of food for the whole living world. Light effects biological activities of plants by its intensity, period and duration. Plants are classified into following two categories on the basis of requirement of light intensity:

• Heliophytes: Plants, which can grow better in bright light are called heliophytes.
• Sciophytes: Plants, which require relatively less of light and they can grow better in shades are called sciophytes.

Question 11.
Explain the meaning of food web and draw its diagram.
Answer:
Food Web: In nature, food-chains are not isolated sequences, but are interrelated and interconnected with one another. When many food-chains operate simultaneously and interlock such pattern is termed as food web. Thus, the food web is a description of feeding connections between the organisms which make up a community. Energy passes through one trophic level to next via these food web links, e.g., a rat feeds on various kinds of grains, fruits, stems, roots, etc.

A rat in its turn is consumed by a snake which is eaten by a falcon. The snakes feed on both frogs and rats. Thus, a network of food-chains exists and this is called food web. The food web gets more complicated because of variability in taste and preference availability and compulsion and several other factors at each level. For example, tigers normally do not feed on fishes or crabs but in Sunderbans they are forced to eat them.

Question 12.
Explain Calcium cycle with well labelled diagram.
Answer:

Question 13.
Draw ecological pyramid of number of a tree ecosystem and grassland ecosystem.
Answer:

Question 14.
What do you mean by ecosystem? Describe the important components of a pond ecosystem.
Or
Write about role of decomposers in an ecosystem with example.
Answer:
Ecosystem: The system resulting from the interaction between organisms and their environment is called as ecosystem.

Components of a pond ecosystem:
A pond ecosystem should contain all components of ecosystems like:

(a) Producers: Organism, which can synthesize their own food are included under producers, e.g., Volvox, Pandorina, Oedogonium, Saggitaria, Utricularia, Azolla, Trapa, Lemna, Typha, Nymphaea etc. form the producer class of the pond ecosystem.

(b) Consumers:

• Primary consumer: Animals, which feed on producers are included into this category e.g., Daphnia, Cyclops, Paramoecium, Amoeba and small fishes.
• Secondary consumers: Primary consumers also serve as food for water sn’akdls, a few tortoise, few types of fish etc. hence, these are carnivores.
• Tertiary consumers : Secondary consumers also serve as food for aquatic birds like kingfisher, cranes, big fish and these together form a top class carnivorous group and called as tertiary consumers.

(c) Decomposers: All producers and consumers die and accumulate on the floor of the pond. Even the waste material and faeces of these animals get accumulated on the floor of the pond. Similarly, the floor of pond is also occupied by decomposers, which include bacteria and fungi. These decomposers decompose complex organic compounds of then- bodies into simpler forms which are finally mixed with soil of floor of ponds. These are again absorbed by the roots of producer plants and thus matter is recycled.

Question 15.
Explain pyramid of biomass of pond ecosystem.
Answer:
The biomass, i.e., the living weight of the organisms in the food-chain present at different trophic levels in an ecosystem forms the pyramid of biomass.

When biomass of consumers is greater than biomass of producer then pyramid is called as inverted pyramid of biomass. eg. pyramid of biomass of pond ecosysyem is always inverted.

Ecosystem: The system resulting from the interaction between organisms and the environment is called as ecosystem.

Ecosystem Long Answer Type Questions

Question 1.
What are ecological pyramids? Explain various types of ecological pyramids.
Answer:
Trophic level: In an ecosystem, the producer consumer arrangement is a kind of structure known as trophic structure and each food level in the food-chain is called as trophic level or energy level. In other, words each level of food in food-chain is called its trophic level. The first trophic level (T,) in an ecosystem is occupied by producers. Herbivores (primary consumers) form second trophic level (T2), secondary consumers form third trophic level (T3), tertiary consumers form fourth trophic level (T4) and decomposers form fifth trophic level (T5) in an ecosystem. .

Food or Ecological Pyramids: If we express the organisms of various trophic levels according to their number, biomass and ratio of energy stores within it, then we obtain ac6ne or pyramid like structure which is known as food or ecological pyramid. Ecological pyramids represent the trophic structure and function of an ecosystem. In base and successive trophic levels the tiers which make up the apex. Ecological pyramids are of the following three types :

1. Pyramid of Biomass
2. Pyramid of number
3. Pyramid of energy.

1. Pyramid of Biomass : Biomass is the dry weight of living organisms per unit of space. The ecological pyramid, which shows the quantitative relationship of the standing crop at each trophic level. The pyramid of biomass shows gradual reduction in biomass at each trophic level from base to apex. The pyramid of biomass may be:

• Upright: e.g., all terrestrial ecosystems.
• Inverted: e.g., all aquatic ecosystems.

2. Pyramid of Number : The ecological pyramid which shows the number of individual organisms at each trophic level. It represents numerical relationship between different trophic level of a food-chain. In this pyramid more abundant species from the first trophic level and from the base of pyramid and the less abundant species remain near the top. The pyramid of number may be:

• Upright: e.g. grassland, pond, forest ecosystem.
• Inverted :e.g. ecosystem of tree.

3. Pyramid of Energy : It indicates the total amount of energy at each trophic level of the food-chain. At each producer level, the total energy available is relatively more than at the higher trophic levels because of the loss of the energy at each trophic level. Thus, there is a gradual loss of energy at each trophic level. The pyramid of energy of each types of ecosystem is always upright.

Question 2.
What is meant by terrestrial biomes? What are its types? Explain any one biomes in detail.
Answer:
Terrestrial Biome : Large area occupying ecosystems in nature are called biomes. If biomes are on land than they are called Terrestrial biomes.
Terrestrial biomes may be:
(a) Forest Biomes : They may be as below;

• Topical rain forest
• Cold tropical forest
• Taiga forest.

(b) Grassland biomes : They may be as below:

• Tropical rain forest
• Cold tropical forest.

(c) Desert Biomes
(d) Tundra Biomes.
Grassland Biome or Ecosystem has long grasses, Its, land is fertile. It receives approximately 25 to 75 cm average rainfall. Its component are:

(a) Abiotic component: All organic, inorganic substances and climatic factors together form abiotic component.

(b) Biotic component :

• Producers: Grasses, herb, shrubs.
• Primary consumers: Herbivore like cow, buffalo, goats, sheep, deer, rabbit, rat insect.
• Secondary consumers: Carnivore animals which eat primary consumers-like snake, birds, foxes, jackal etc.
• Tertiary consumers: These organism which eat secondary consumers because no other one eats them like Hawk, Peacock, etc.
• Decomposers: Micro-Fungus, Bacteria, actinomycetes are decomposer of grassland biomes and recycle the material back to soil and used by producers.

Question 3.
What are Biogeochemical cycles? Write in short sulphur and calcium cycle.
Answer:
All living organisms get matter from the biosphere components i.e„ lithosphere, hydrosphere and atmosphere. Essential elements or inorganic substances are provided by earth and are required by organisms for their body building and metabolism, they are known as Biogeochemicals or biogenetic nutrients.

Sulphur Cycle : Producers (green plants) need sulphur in the form of sulphates from soil or from water (aquatic plants). The animals get sulphur through food. Some animals get sulphur from water also. Sulphur is found in three amino acids hence, sulphur is component of most proteins, some vitamins and enzymes. Plants pick up sulphur in the form of sulphates. They are converted to organic form mostly as component of some amino acids. It is found in nature as element and also as sulphates in soil, water and rocks. After the death of plants and animals, they are decomposed by microbes like Asperigillus, Neurospora and Escherichia releasing hydrogen sulphide.

Calcium cycle : Calcium is slowly released from the rocks by water and wind action. These are either blown into the air or absorbed by plants through their roots. Animals obtain it directly as compounds and also from plants. Calcium is released from plant and animal bodies by decomposition after death. Molluscs and corals deposit a large quantity of calcium in their shells and skeletons making it unavailable for quick cycling.

MP Board Class 12th Biology Solutions

MP Board Class 12th Biology Solutions Chapter 4 Reproductive Health

Reproductive Health NCERT Textbook Questions and Answers

Question 1.
What do you think is the significance of reproductive health in a society?
Answer:
Significance of reproductive health in a society are :

• Control over the transmission of STDs.
• Less death due to reproduction related diseases like-AIDS, cancer of reproductive tract.
• Control in population explosion.
• Not only this reproductive health of men and women affects the health of the next generation.

Question 2.
Suggest the aspects of reproductive health which need to be given special attention in the present scenario.
Answer:
Special attention need to be given to the following aspect :

• Introduction of sex education in school that to helps in eradicating myths and mis-conceptions regarding sex-related aspects.
• Proper information about reproductive organs, safe and hygienic sexual practices and sexually transmitted diseases.
• Awareness of problems due to uncontrolled population growth, social evils like sex abuse and sex-related crimes etc.
• Strong infrastructural facilities, professional expertise and material support to provide medical assistance and care to people in reproduction related problems.
• Educating people about available birth control options, care of pregnant mothers, post-natal care of mother and child, importance of breast feeding, equal opportunities for the male and female child.

Question 3.
Is sex education necessary in schools? Why?
Answer:
Yes, sex education is necessary in schools because :

• It will provide proper information about reproductive organs, adolescence, safe, hygienic sexual practices and Sexually Transmitted Diseases (STDs).
• It will provide right information to avoid myths and misconceptions about sex related queries.

Question 4.
Do you think that reproductive health in our country has improved in the past 50 year’s ? If yes, mention some such areas of improvement
Answer:
Yes, Reproductive health in our country has improved in the last 50 year’s.

Some areas of improvement are :

• Better awareness about sex-related matters.
• Increased number of medically assisted deliveries and better post-natal care of child and mother leading to decreased maternal and infant mortality rates.
• Increased number of couples with small families.
• Better direction and cure of STDs and overall increased medical facilities for all sex-related problems.

Question 5.
What are the suggested reasons of population explosion?
Answer:
The situation where population exceeds productive capacity is known as population explosion. In nature, the amount of resources are limited hence, if the population increases in the present rate and increasing beyond the limit, they (Resources) would get exhausted.
Reasons of population explosion : Following are the reasons of population explosion:

• Increasing birth rate.
• Decreasing death rate.
• Higher rate of reproduction.
• Medical services have brought down mortality due to fatal diseases and epidemics.
• Lack of predator in the civilized world today, the only predator of man is man himself.

Question 6.
Is the use of contraceptives justified ? Give reasons.
Answer:
Yes, use of contraceptive is justified because it helps to control the rapid growth of human population. It will also help in preventing unwanted pregnancies and STDs. Contraceptive also help in controlling the population growth rate.

Question 7.
Removal of gonads can not be considered as a contraceptive option, why?
Answer:
Removal of gonads not only stops the production of gametes but will also stop the secretions of various important hormones, which are important for bodily functions. This method is irreversible and thus, can not be considered as a contraceptive method.

Question 8.
Amniocentesis for sex determination is banned in our country. Is this ban necessary? Comment
Answer:
Yes, the ban is necessary because amniocentesis is misused for determining the sex of the fetus and then aborting the child of it is a female. This process is illegal it causes harm to the fetus as well as mother it can also disturb the sex ratio.

Question 9.
Suggest some method to assist infertile couples to have children.
Answer:
If the couples are enable birth the children and corrections are not possible, the couples could be assisted to have children through certain special techniques, commonly known as Assisted Reproductive Technologies (ART). Some methods are given as :

1. In Vitro Fertilization (IVF) : In this method, ova from the female and the sperm from the male are collected and induced to form zygote under stimulated conditions in the laboratory. This process is called In Vitro Fertilization (IVF). Some method given as follows :

(i) Zygote Intrafallopian Transfer (ZlFT) : The zygote or early embryo with up to 8 blastomeres is transferred into the fallopian tube.

(ii) Intra Uterine Transfer (IUT) : Embryo with more than 8 blastomeres is transferred into the uterus in females who cannot conceive embryos formed by fusion of gametes in another female are transfered.

(iii) Test tube baby : In this method, ova from the donor (female) and sperm from the donor (male) are collected and are induced to form zygote under stimulated conditions in the laboratory. The zygote could then be transferred into the fallopian tube and embryos transferred into the uterus, to complete its further development. The child born from this method is called test tube baby.

(2) Gamete Intra Fallopian Transfer (GIFT) : It is the transfer of an ovum collected from a donor into the fallopian tube 8 another female who cannot produce one, but can provide suitable environment for fertilization and further development of the embryo.

(3) Intra Cytoplasmic Sperm Injection (ICSI) : It is a procedure to form an embryo HI* the laboratory by directly injecting the sperm into an ovum.

(4) Artificial Insemination (AI) : In this method, the semen collected either from the husband or a healthy donor is artificially introduced into the vegina or into the uterus (Intra Uterine Insemination, IUI). This technique is used in cases where the male is unable to inseminate sperms in the female reproductive tract or due to very low sperm counts in the ejaculation.

(5) Host Mothering : In this process, the embryo is transferred from the biological mother to a surrogate mother. The embryo then develops till it is fully developed or partially developed. It is then transferred to the biological mother or into any other. This technique is useful for females in which embryo forms but is not able to develop.

Question 10.
What are the measures one has to take to prevent from contracting STDs ?
Answer:
STDs can be prevented by the following methods :

• Avoid sex with unknown partners/multiple partners.
• Always use condoms during coitus.
• Always contact a qualified doctor for any doubt in early stage of infection and get complete treatment if diagnosed with disease.

Question 11.
State True/False with explanation.
(a) Abortions could happen spontaneously too. (True/False)
Answer:
False, Abortion does not happen under normal conditions. It happens accidently or under the will of Parents.

(b) Infertility is defined as the inability to produce a viable offspring and is always due to abnormalities/defects in the female partner. (True/False)
Answer:
False, Sterility always does not occur due to female sometimes. Males are also responsible for this.

(c) Complete lactation could help as a natural method of contraception. (True/False)
Answer:
True, Menstrual cycle does not occur after parturition which can act as natural
contraception but this method is functional for a period of six months from parturition.

(d) Creating awareness about sex related aspects is an effective method to improve reproductive health of die people. (True/False)
Answer:
True, this creates better reproductive health among people.

Question 12.
Correct the following statements :
(a) Surgical methods of contraception prevent gamete formation.
Answer:
It prevents the transportation of gametes not their formation.

(b) All sexually transmitted diseases are completely curable.
Answer:
Hepatitis-Band AIDS are not curable.

(c) Oral pills are very popular contraceptives among the rural women.
Answer:
Oral pills are not popular among rural women. They require sex education.

(d) In E.T. techniques, embryos are always transfered into the uterus.
Answer:
In E.T. techniques 8-called blastomere is transfered into the fallopian tube. While more than 8-celled blastomere is transfered into the uterus.

Reproductive Health Other Important Questions and Answers

Reproductive Health Objective Type Questions

1. Choose the Correct Answer
Question 1.
Removal of Fallopian tube in females are called :
(a) Vasectomy
(b) Tubectomy
(c) Ovariectomy
(d) Castration (Gonadectomy).
Answer:
(b) Tubectomy

Question 2.
Main region ofthe population growth are :
(a) Less death rate
(b) Growth of birth rate
(c) Drought
(d) Less war.
Answer:
(a) Less death rate

Question 3.
The causes of popülatîon explosion in large cities is :
(a) Chances of education
(b) Available facilities
(c) Sources of income
(d) All of these.
Answer:
(d) All of these.

Question 4.
Population density is more in :
(a) USA
(b) India
(c) China
(d) Japan.
Answer:
(c) China

Question 5.
AIDS disease caused by :
(a) From bacteria
(b) From protozoa
(c) From virus
(d) From fungus.
Answer:
(c) From virus

Question 6.
Sex transmitted diseases are caused by :
(a) Virus
(b) Bacteria
(c) Protozoa
(d) All of these.
Answer:
(a) Virus

Question 7.
Population calculated in India :
(a) In 1891
(b) In 1947
(c) In 1950
(d) In 1961.
Answer:
(a) In 1891

Question 8.
The technique of the control of birth rate is called :
(a) TUD
(b) GIFT
(c) MIF
(d) IVEET.
Answer:
(a) TUD

Question 9.
Alcohol affected organ is :
(a) Liver
(b) Cerebrum
(c) Cerebellum
(d) Heart
Answer:
(a) Liver

Question 10.
Population growth rate of world is :
(a) 2-4%
(b) 2%
(c) 3%
(d) 4%.
Answer:
(b) 2%

2. Fill in the Blanks :

1. Statistical study of population is called ……………….
2. According to MALTHUS, Population grows ……………….whereas the means of its subsistences grows ……………….
3. The entry and exit of member in any population is called ……………….
4. Cutting and ligating ends of segments of vas deferens is called ……………….
5. The population density of terrestrial animals, the area is represented by ……………….
6. Birth rate and migration ………………. the population density.
7. Revised birth fate is always greater than ………………. birthrate.
8. Vital index = ………………. /Mortality x 100.
9. Population ………………. with time and place.
10. From the population point of view, every ………………. person in the world, is an Indian.

Answer:

1. 1. Demography
   2. Geometrically
   3. Migration
   4. Vasectomy
   5. Meter2 (m2)
   6. Growth
   7. Unrevised
   8. Natality
   9. Changes
   10. Sixth.

3. Match the Following :

Answer:

1. (c)
2. (e)
3. (a)
4. (b)
5. (d).

Answer:

1. (c)
2. (d)
3. (e)
4. (b)
5. (a).

III. Answer in One Word/Sentence:

1. Write two such causes by which unchecked growth takes place. (SSCE 1992)
2. Write the full name of IUCD. (SSCE 1992!)
3. What we called the study of human population?
4. What type of chemical contraceptive is found in Mala-D and N?

Answer:

1. Early marriage, illiteracy
2. Intra-Uterine Contraceptive Devices
3. Demography
4. Oestrogen and Progesteron hormone.

Reproductive Health Very Short Answer Type Questions

Question 1.
What is the other name of family planning?
Answer:
The other name of family planning is “Parivar Kalyan”.

Question 2.
Where is Central Drug Research Institute located ?
Answer:
Central Drug Research Institute (CDRI) is located in Lucknow (Uttar Pradesh).

Question 3.
Write one benefit of condom.
Answer:
Condom provided protection from Sexually Transmitted Diseases (STDs).

Question 4.
What is the name of contraceptive pills which is taken only in once in a week ?
Answer:
“Saheli.”

Question 5.
Write the full form of IUCD.
Answer:
Intra Uterine Contraceptive Device.

Question 6.
Write the full form of STDs.
Answer:
Sexually Transmitted Disease.

Question 7.
What is the legal age for marriage of male and female in India ?
Answer:
For male 21 Year and for female 18 years.

Question 8.
Write the name of two STDs which are spread through infected blood.
Answer:
AIDS, Hepatitis-B.

Question 9.
Write the name of two disease which are caused by sexual contact
Answer:
Gonorrhoea, Syphilis.

Question 10.
Write the full form of HIV and AIDS.
Answer:
HIV : Human Immunodeficiency Virus.
AIDS : Acquired Immuno Deficiency Syndrome.

Question 11.
Write the full form of ZIFT.
Answer:
Zygote Intra Fallopian Transfer.

Question 12.
What is the process for surgical sterilization in males called ?
Answer:
Vasectomy.

Reproductive Health Short Answer Type Questions

Question 1.
What is test-tube baby ?
Answer:
In some cases, a woman is unable to have a normal fertilization to bear the child. In such cases, test-tube technique may be successful. In this technique, the unfertilized eggs of such woman is isolated in aseptic condition and fertilized it in test-tube by the sperms of her husband. The fertilized egg or blastocyst can be maintained in vitro till it gets 32 celled stage. It can be implanted in the uterus of the female. The female remains under the supervision of doctor till completion of gestation period of 280 days. The baby produced in such a way is called a test-tube baby.

Question 2.
What is GIFT ? Explain in brief.
Answer:
GIFT (Gametes Intra Fallopian Transfer): It is a latest technique to produce a child. In this technique, the gametes are kept separately in a catheter and injected directly into the fallopian tube of the woman using laproscopy. Thus, in this case, fertilization occurs inside the body of woman. Prior to injection of gametes, the mother would be given hormones for about a week to stimulate follicle formation. This causes development of several eggs i.e,, super ovulation. The first GIFT in India was done in Mumbai and twins were born in August, 1990.

Question 3.
Explain the following:

1. Tubectomy
2. Vasectomy.

Answer:

1. Tubectomy : The surgical removal of a segment of oviduct and then ligating the cut end is called tubectomy. It is applied in females to check the pregnancy.
2. Vasectomy : Surgical cutting and ligating ends of segments of vas deferens is called vasectomy.

Question 4.
What is amniocentesis ? Write its ill effects and two advantages.
Answer:
Amniocentesis : It is prenatal diagnostic technique in which amniotic fluid of uterus is isolated by a surgical needle and foetus cells are cultured on a culture medium and chromosomes are examined. This technique is used to understand the following things or Advantages :

• Chromosomal abnormalities like that of Down’s syndrome, Philadelphia syndrome and Edward’s syndrome.
• Metabolic disorders like that of PKV, Cretinism, Alkaptonuria, etc.
• Sex of the embryo can be examined by this technique.
• Effects of amniocentesis: Due to this type of test, the female embryos are being eradicated. This leads into the
• decrease in number of females which may cause a serious problem.

Question 5.
Explain the social causes of human population growth.
Answer:
Social causes of human population growth rate are:

• Illiteracy in society.
• Low level of society.
• Various orthodox tradition like son leads to progeny.
• Social barriers.
• Early child marriage presuming that after mid-age marriage reproductive capacity degenerates.
• Social backwardness.
• Social set-up that “Putra Ratan se Moksh milta hai”.

MP Board Class 12th Biology Solutions

MP Board Class 12th Biology Solutions Chapter 15 Biodiversity And Conversation

Biodiversity and Conversation NCERT Text Book Question and Answers

Question 1.
Name the three important components of biodiversity.
Answer:
Three important components of biodiversity are :

1. Genetic diversity.
2. Species diversity.
3. Ecosystem diversity.

Question 2.
How do ecologists estimate the total number of species present in the world?
Answer:
The diversity of living organisms present on the earth is very vast. According to an estimate by researchers, it is about seven millions. The total number of species present in the world is calculated by ecologists by statistical comparison between a species richness of a well studied group of insects of temperate and tropical regions. Then, these ratios are ‘ extrapolated with other groups of plants and animals to calculate the total species richness present on the earth.

Question 3.
Give three hypotheses for explaining why tropics show greatest levels of species richness.
Answer:
There are three different hypotheses proposed by scientists for explaining species richness in the tropics :

1. Tropical latitudes receive more solar energy than temperate regions, which leads to high productivity and high species diversity.
2. Tropical regions have less seasonal variations and have a more or less constant environment. This promotes the niche specialization and thus, high species richness.
3. Temperate regions were subjected to glaciations during the ice age, while tropical regions remained undisturbed which led to an increase in the species diversity in this region.

Question 4.
What is the significance of the slope of regression in a species-area relationship?
Answer:
The slope regression (z) has a great significance in order to find a species-area relationship, it has been found that in smallar areas (where the species-area relationship is analyzed), the value of slopes of regression is similar regardless of the taxonomic group or the region. However, when a similar analysis done in larger areas, then the slope of regression is much steeper.

Question 5.
What are the major causes of species losses in geographical regions?
Answer:
The following are the major causes for the loss of biodiversity around the world:
1. Habitat loss and fragmentation: Habitats of various organisms are altered or destroyed by uncontrolled and unsustainable human activities such as deforestation, slash and burn agriculture, mining, and urbanization. This results in the breaking up of the habitat into small pieces, which effects the movement of migratory animals and also, decreases the genetic exchange between populations leading to a declination of species.

2. Over-exploitation: Due to over-hunting and over-exploitation of various plants and animals by humans, many species have become endangered of extinct (such as the tiger and the passenger pigeon).

3. Alien species invasions: Accidental or intentional introduction of non-native species into a habitat has also led to the declination or extinction of indigenous species. For example, the Nile perch introduced in lake Victoria in Kenya led to the extinction of more than two hundred species of native fish in the lake.

4. Co-extinction: In a native habitat, one species is connected to the other in an intricate network. The extinction of one species causes the extinction of other species, which is associated with it in an obligatory way. For example, the extinction of the host will cause the extinction of its parasites.

Question 6.
How is biodiversity important for ecosystem functioning?
Answer:
An ecosystem with high species diversity is much more stable than an ecosystem with low species diversity. Also, high biodiversity makes the ecosystem more stable in productivity and more resistant towards disturbances such as alien species invasions and floods.

If an ecosystem is rich in biodiversity, then the ecological balance would not get affected. Various tropic levels are connected through food chains. If any one organism or all organisms of any one trophic level is illed, then it will disrupt the entire food chain. For example, in a food chain, if all plants are killed, then all deer’s will die due to the lack of food.

If all deer’s are dead, soon the tigers will also die. Therefore, it can be concluded that if an ecosystem is rich in species, then there will be other food alternatives at each trophic level which would not allow any organism to die due to the absence of their food resource. Hence, biodiversity plays an important role in maintaining the health and ecological balance of an ecosystem.

Question 7.
What are sacred groves? What is their role in conservation?
Answer:
Sacred groves are forest patches for worship in several parts of India. All the trees and wildlife in them are again treated and given total protection. They are found in khasi and jointia hills in Meghalaya. Westen Ghat regions of Karnataka and Maharashtra, etc. Tribals do not allow anyone to cut even a single branch of tree in these sacred groves thus sacred groves have been free form all types of exploitations.

Question 8.
Among the ecosystem services are control of floods and soil erosion, how is this achieved by the biotic components of the ecosystem?
Answer:

• Control of soil erosion: Plant roots hold the soil particles tightly and do not allow the top soil to be drifted away be winds or moving water. Plants increase the porosity and fertility of the soil.
• Control of floods: It is carried out by retaining water and preventing run off rain water. Litter and humus of plants function as sponges thus, retaining the water which percolates down and get stored as underground water. Hence, the flood is controlled.

Question 9.
The species diversity of plants (22 %) is much less than that of animals (72 %). What could be the explanations to how animals achieved greater diversifications?
Answer:
Animals have achieved greater diversification than plants due to following reasons:
1. They are mobile and thus can move away from their predators or unfavourable environments. On the other hand plants are fixed and have fewer adaptations to obtain optimum amount of raw materials and sunlight therefore, they show lesser diversity.

2. Animals have well developed nervous system to receive stimuli against external factors and thus can respond to them. On the other hand, plants do not exhibit any such mechanism, thus they show lesser diversity than animals.

Question 10.
Can you think of a situation where we deliberately want to make a species extinct? How would you justify it?
Answer:
Yes, there are various kinds of parasites and disease causing microbes that we deliberately want to eradicate from the earth. Since these micro-organisms are harmful to human beings, scientists are working hard to fight against them. Scientists have been able to eliminate smallpox virus from the world through the use of vaccinations. This shows that humans deliberately want to make these species extinct. Several other eradication programmes such as polio and hepatitis B vaccinations are aimed to eliminate these disease causing microbes.

Biodiversity and Conversation Other Important Questions and Answers

Biodiversity And Conversation Objective Type Questions

Choose the Correct Answer:

Question 1.
Wildlife conservation act was inforced in India in:
(a) 1883
(b) 1972
(c) 1973
(d) 1982.
Answer:
(b) 1972

Question 2.
Indian board of wildlife was established in:
(a) 1952
(b) 1981
(c) 1971
(d) 1972.
Answer:
(a) 1952

Question 3.
NBPGR is situated at:
(a) Delhi
(b) Kolkata
(c) Lucknow
(d) Mumbai.
Answer:
(a) Delhi

Question 4.
Number of biosphere in our country is :
(a) 73
(b) 7
(c) 416
(d) 23
Answer:
(b) 7

Question 5.
National park related with white tiger is:
(a) Kanker
(b) Satipada
(c) Bandhavgarh
(d) Kanha.
Answer:
(c) Bandhavgarh

Question 6.
The first national park of Madhya Pradesh is :
(a) Shivpuri
(b) Bandhavgarh
(c) Kanha
(d) Kanker.
Answer:
(c) Bandhavgarh

Question 7.
Plant fossils national park is situated in :
(a) Shivpuri
(b) Mandala
(c) Kanha
(d) Kanker.
Answer:
(b) Mandala

Question 8.
Kanha national park is famous for:
(a) Rhinoceros
(b) Tiger
(c) Birds
(d) Aligator.
Answer:
(b) Tiger

Question 9.
Bandipur national park is the habitat of:
(a) Deer Project
(b) Peacock Project
(c) Elephant Project
(d) Tiger Project
Answer:
(d) Tiger Project

Question 10.
Animal which is extinct in india:
(a) Hippopotamus
(b) National Park
(c) Cheetah
(d) Wolf
Answer:
(c) Cheetah

Question 11.
Which is in-situ conservation method:
(a) Tissue culture’
(b) National park
(c) Botanical garden .
(d)Cryotest.
Answer:
(b) National park

Question 12.
Which of the following are not done in a wild sanctuary:
(a) Conservation of flora
(b) Conservation of fauna
(c) Use of soil and flora
(d) Prohibition of hunting.
Answer:
(c) Use of soil and flora

Question 13.
In India maximum area covered by forest
(a) Odisha
(b) Arunachal Pradesh
(c) Madhya Pradesh
(d) All of the above
Answer:
(b) Arunachal Pradesh

Question 14.
Forest destruction:
(a) Destruction of natural sources
(b) Environmental Pollution
(c) Genetic disorder
(d) All of the above
Answer:
(b) Environmental Pollution

Question 15.
Forest Research Institute (FRI) is situated in:
(a) Shimla
(b) Chennai
(c) Dehradun
(d) Kolkata.
Answer:
(c) Dehradun

Question 16.
World environmental day is celebrated on :
(a) 15th March
(b) 15th April
(c) 4th May
(d) 5th June.
Answer:
(d) 5th June.

Question 17.
Species which are continuously distinct:
(a) Long lasting animal
(b) Dangerous animal
(c) Simple animal
(d) None of these.
Answer:
(c) Simple animal

Question 18.
Kaziranga national park is situated in:
(a) West Bengal
(b) Kerala
(c) Assam
(d) Umariya.
Answer:
(c) Assam

Question 19.
Bandhavgarh national park is situated in:
(a) Satana
(b) Shivpuri
(c) Mandla
(d) Umariya.
Answer:
(d) Umariya.

Question 20.
Kanha national park is located in :
(a) Uttar Pradesh
(b) Rajasthan
(c) Gujrat
(d) Madhya Pradesh.
Answer:
(a) Uttar Pradesh

Question 21.
National wildlife (Protection) Act was formulated during:
(a) 1972
(b) 1974
(c) 1976
(d) 1978.
Answer:
(a) 1972

Question 2.
Fill in the Blanks:

1. Planting of trees and forests on waste land is called ……………………..
2. Wildlife protection act is come in force in …………………….
3. UNESCO has started Man and Biosphere programme in ……………………..
4. ………………….. is the first Biosphere Reserve of India.
5. Kajiranga wildlife sanctuary is famous for ………………………
6. Red Data book is related with ……………………..
7. World Environment Day is celebrated on ………………………… of every year.
8. FRI is situated at ……………………..
9. …………………….. is the main source of energy.
10. National parks are made for the conservation of ……………………….
11. ………………………….. is the main region of forest depletion.
12. Indian Lion and Cheetah is ……………………….. animal.
13. ………………………….. is called the development of forest on barren land.
14. World environment day celebrated on ………………………

Answer:

1. 1. Afforestation
   2. 1972
   3. 1971
   4. Nilgiri
   5. Rhinoceros
   6. Endangered species
   7. 5th June
   8. Dehradun
   9. Sun
   10. Threatened species

1. Growing population
2. Rare
3. Forestration
4. 5th June.

Question 3.
Match the Following:

Answer:
1. (c)
2. (d)
3. (e)
4. (b)
5. (a).

Answer:
l.(e)
2. (d)
3. (a)
4. (b)
5. (c).

Question 4.
Answer in One Word/Sentence:

1. In which place of India, lion is found?
2. When does World Environment Day is celebrated?
3. When does Wildlife Protection Act was formed in India?
4. In which state Ghana bird Sanctuary is situated?
5. Where is Tiger Project situated?
6. Name any two National Parks of India.
7. Where does Kanha National Park situated?
8. Name any two threatened species.
9. Name the state having maximum forest area.
10. Name the National Animal and National Bird of India.
11. Name any one book associated with the conservation of wildlife.

Answer:

1. Gir forest, Gujarat
2. 5th June
3. 1972
4. Bharatpur, Rajasthan,
5. Kanha, M.P.
6. Rajaji Park and Gir National Park
7. M.P.
8. Lion, Wild buffalo
9. Chattisgarh (C.G.)
10. Tiger and Peacock
11. Red Data Book.

Biodiversity And Conversation Very Short Answer Type Questions

Question 1.
When does WLF-India was established?
Answer:
1962.

Question 2.
Where does Tiger project is established in Madhya Pradesh?
Answer:
Kanha national park.

Question 3.
Where does wild Ass is found?
Answer:
Runn of Kutch.

Question 4.
Where does great Indian bustards are found in India?
Answer:
Rajasthan, Punjab, Gujrat.

Question 5.
Write other name of biodiversity.
Answer:
Biological diversity.

Question 6.
Which part of the world are known as lesser biodiversity?
Answer:
Poles has lesser biodiversity.

Question 7.
What is the basic concept of biodiversity of biosphere?
Answer:
Gene.

Question 8.
Name the two plants which are worshiped any two states.
Answer:

1. Kadamba in Rajasthan.
2. Mango in Odisha.

Question 9.
Which part of the world which has more biodiversity?
Answer:
In Brazil.

Question 10.
Write the full form of IUCN.
Answer:
International Union for Conservation of Nature and Natural Resources.

Question 11.
Who perform important role in nature balancing?
Answer:
Forest animals.

Question 12.
Name the branch of science in which done the study of forest animal conservation.
Answer:
Forestry.

Question 13.
When, started the programme of social forestry?
Answer:
1976

Question 14.
Write the modern name of sanctuary.
Answer:
Shelter.

Biodiversity And Conversation Short Answer Type Questions

Question 1.
Explain conservation of biodiversity.
Answer:
Conservation of biodiversity: India is one of the richest (among the 12 mega centres of the world) countries in biological diversity. This rich biodiversity is due to a variety of climatic conditions prevailing on different ecological habits ranging from tropical, subtropical, temperate, alpine to desert. These varied conditions harbour a plethora of organisms, which forms an important natures wealth, responsible for socio-economic development of life in our country. But the biodiversity of organisms are under serious threat and there is an urgent need for biodiversity conservation on war foot level.

Question 2.
What is social forestry?
Answer:
The planning of social forestry started in India since 1976, which is related with the conservation of forests. This project is useful for local people in various ways, such as it fulfil their requirements, provides work to unemployed, use of wasteland and help to maintain O₂ and CO₂ balance in the atmosphere, etc. Thus, project is started by Indian government, the chief objectives of this project are as follows :

• Plantation of useful plants in the forest.
• Development of forests on personal lands by the cooperation of government.
• To prevent the harmful effects of pollution by development of artificial forest.
• Preservation of endangered wild animals.

Question 3.
Write importance of forests.
Answer:
Importance of forests :
1. Forests play a vital role in the life and economy of all tribes living in forests, by providing food, medicines and other products of commercial value.

2. Forests are large biotic communities. It provides shelter and sustenance to a larger number of diverse species of plants, animals and microorganisms.

3. Forests prevent soil erosion by wind and water. The trees provide shade which prevents the soil from drying during summer. Trees reduce the velocity of raindrops or wind striking the ground so that dislodging of the slil partiles is reduces. The root system of plants firmly binds the soil.

 

Question 4.
Write any five features of Indian forests.
Answer:
Indian forests are characterized by :

1. Indian forests are mainly tropical forests.
2. Himalayan forests are characterized by the presence of coniferous trees.
3. In few parts of our country having temperate forests.
4. Our forests contain a large number of useful varieties of plants and animals.
5. A great variations are present in indian forests.

Question 5.
Enumerate any five reasons for the destruction of wildlife (animals).
Answer:
The main reason of destruction of wildlife (animals) are:

• Entertainment, personal profit, earning money by wrong methods are the human illattitudes, unkindness toward wild animals has brought the animals at endanger level.
• Huge reduction in the natural habitat of wild animal so.it has reduced their living area due to urbanization, industrialization and deforestation.
• Exhorbitant extraction and consumption is harmful for wild animals like skin of animals, Teeth of elephant etc.
• Various types of pollution has force the reduction of wild animals. .
• Very loose and unpunishable, wildlife act which has increase poaching, huntidg of wild animals.

Biodiversity And Conversation Long Answer Type Questions

Question 1.
What do you understand by Threatened species? Explain its types.
Answer:
Species which have been greatly reduced in their number or whose natural habitats have been disturbed due to which these are near extinction and may become extinct if the causative factors continue are called threatened species. It is estimated that about 25,000 plant species and 1,000 vertebrate species and subspecies and many invertebrate species are threatened with extinction. It is believed that at least 10% of the living species are in danger.
The organisms which are near extinction are of following types :

1. Endangered (E) species: The species which are facing danger of extinction and whose survival is unlikely if the causal factors continue to operate. These are the species whose number have been reduced to a critical level or whose habitats have been so drastically reduced that they are deemed to be in immediate danger of extinction. For example, Indian rhinoceros, Asiatic lion and the great Indian bustard, snow leopard etc.

2. Vulnerable (V) species: These are the species having sufficient number of individuals in their natural habitats. However, in the near future, they might represent the category of endangered species if unfavourable factors in the environment continue to operate. e.g„ Musk deer, black buck, golden langur, etc.

3. Rare (R) species: These are species with small population in the world. At present these are not endangered and vulnerable but are at risk. These species are usually localize within geographical areas or habitats or are thinly scattered over a more extensive range. e.g., Indian elephant, Asiatic wildass, gharial, wild yak etc.

4. Threatened (T) species: The species which do not fall under the endangered or vulnerable categories but indications are available that such species may come under any of these two categories if appropriate measures are not taken to protect them.

Question 2.
What are National Parks? Explain any five National Parks found in India.
Answer:
Natinal park is an area which is strictly reserved for the betterment of the wildlife and where activities like forestry, grazing or cultivation are not permitted.
Five national parks of India are :

1. Shivpuri park: It is located at Shivpuri near Gwalior (Madhya Pradesh). Wildlife present in this park tiger, cheetal, sambhar.
2. Gundi deer park: It is locssssated near Chennai (Madras) in Tamil Nadu. Wildlife found here are Alvino deer, black buck, cheetal and famous snake park.
3. Betia national park: It is located in Palamu at Bihar. Wildlife found in this national park are elephant, tiger.
4. Dachigham national park: It is located at Srinagar in Jammu and Kashmir. Wildlife
   leopard, black beer, brown bear, musk deer, hangul, scrow, etc.
5. Bandhavgarh national park: It is located at Shahdol in Madhya Pradesh. Wildlife such as white tiger, panther, cheetal, bison, nilgai, barking deer, wild boar, etc. are found here.

Question 3.
Write in brief, the reasons necessary for conservation of wild species.
Answer:
Necessity for wildlife conservation : The conservation of wildlife is required . for the following reasons:

1. To maintain balance in nature: The wildlife helps us in maintaining the balance of nature. Once this equilibrium is disturbed it leads to many problems. The destruction of carnivores or insectivores often leads to an increase in the herbivores which in turn affects the forest vegetation or crop.

2. Economic value: The wildlife can be used commercially to earn money e.g., Animal products like hides, ivory, fur etc. are of tremendous economic value. The collection and supply of dead or living specimens of wildlife for museums and zoos fetches good amount of money. Wildlife can increase our earning of foreign exchange if tourism is promoted properly.

3. Scientific value: The preservation of wildlife helps many naturalists and behaviour biologists to study morphology, anatomy, physiology, ecology and behaviour biology of the wild animals under their natural surroundings.

4. Recreational value: The wildlife of any country provides best means of sports and recreation. Bird-watching is a hobby of many people all over the world. A visit to the parks and sanctuaries is an enjoyable proposition for children as well as for adults.

5. Cultural value: The wildlife of India is our cultural asset and has deep rooted impact on Indian art, sculpture, literature andreligion. Indus valley civilization shows the use of animals symbols in their seals.

6. Preservation of human race: The destruction of wildlife in an area may eventually lead to the end of human civilization.

Question 4.
Describe the National and International efforts prescribed for the conservation of forests.
Answer:
The forest conservation is started in India on national level since British government. In 1856, Lord Dalhousi had formulated a policy for the conservation of forest in Burma. In 1894, Indian government also prepared a forest policy on national level. The main points of this policy are:

• Forest management,
• Proper use of forest land,
• Policy for protected forests,
• Improved forest production.

Indian government established national parks, sanctuaries and zoological parks. The F.A.O. of United Nations is also functioning on forest conservation on international level. This organization also provides financial help for this purpose. In 1952, Indian government also prepared India’s New National Forest Policy under the direction of F.A.O. Forest policy has been planned for

• Prevention of deforestation of hill plants.
• Reforestation of grazing land.
• Development of grazing land,
• Plantation of economically useful forest trees.
• Increase in the profit of government from forests.

Question 5.
Write a short note on wild animals in India.
Answer:
India as a country has a diverse range of wildlife. India is home for many species of wild animals. More than 25% land are dense forest in India and around 400 national parks. Some of the most important and popular wild animals in India are as follows :
(A) Animals: In Indian forest, below mentioned animals are found :

1. Deer: Its many species are found in India-e.g. Musdeer, Sambhar deer, chital, etc.
2. Antelope: These are same as deer e.g.-Nilgai, Barasingha (Swamp deer), four- homed antelope (chousingha) etc.
3. Elephant: Elephants are large mammals of the family elephantidae. It is found in Kerela and North India.
4. Rhinoceros: It is found in Himalaya region and in the forest of Bengal and Assam. Humans are the biggest threat to
5. the Indian rhinoceros as the have been hunted to the brink of extinction for their horns.
6. Wild Ass: Wild asses are not found in any part of the world. Now in India, it is found in die little Rann of Kutch in the Gujrat state of India.

Carnivorous animals: Some India wild carnivores are :

(a) Indian lion (Asiatic lion): Now it is confined to forests in the fall.
(b) Cheetah: It is on the verge of extinction.
(c) Lion: Lion is a national animal, at present its population in our country are more than 3,000.
(d) Leopard: It is similar in cheetah but smaller than cheetah.

(B) Birds: Peacock, wild fowl, many types of duck, stork, pigeons, partridge, quail, vulture, kite, piquant, owl, indian paradise flycatcher (dudhraj) are found in forests of our country.

(C) Reptiles: Crocodiles, alligators, tortoise, lizards, snakes and other reptilians are found in Indian forest.
Many vertebrates and invertebrates are also found in Indian forest.

Question 6.
What is the main rules of Indian forest act?
Answer:
The Indian forest act, 1927 was largely based on previous Indian forest acts implemented under the British. Things which are included in this act are as follows :

• Forest arrangement: Due to this act give the protection and arrangement to forest and wildlife.
• Appropriate use of forest land: Uses of extra land for forest animals and grow some plant these are useful in wild animals.
• Act for protection of forest: This act, stop passion of deforestation and must be conservation of forest and wild animals.
• Increasing of forest product: Due to this act try to increasing of forest product and discovered new information which are better for wildlife.

Question 7.
Write an essay on measures of forest conservation.
Answer:
Forest conservation: Forest conservation and management are essential to maintain the forests in their natural state and also to prevent the depletion of wildlife and forest wealth. For the success of conservation it is necessary to know the cause of depletion and destruction of forests. Forests are generally destroyed by fire, improper cutting of trees and by animals.

Essentiality of forest conservation: Forest is a complex system which is responsible for the ecological balance in nature. Deforestation causing natural imbalance and affects the biotic components of the environment resulting floods, drought, epidemics, environmental pollution. Many ecologically important species of plants and animals are lost due to which economically important substance like wood, medicines, resin, lac and various food materials will not be available for us.

Measures of forest conservation: The following measures or efforts are prescribed for reforestation:

• Establishment of conserved forests and their conservation in proper way.
• Reforestation on deforested land. Old and damaged plants would be replaced by new plants.
• Proper management of forests.
• By promoting public awareness about forests.
• Replacement of burnt off areas of the forests.
• Plantation of trees that increase forest productivity.
• Forestation of plants on hills and wastelands and prevention of grazing by cattle.
• Prevent forests from fire, diseases and insects.
• Providing basic protection for all forests by law.
• Regulating human activity in the forest such as grazing by cattle and collection of firewood and fodder etc.
• Provide special attention for the conservation of endangered plant and animal species under the inspection of specialists.
• Removal of undesirable trees and vegetation for the better growth of desirable species.
• Forestation of industrially useful plants.
• The government will arrange the management of useful forests.

MP Board Class 12th Biology Solutions

MP Board Class 12th Biology Solutions Chapter 3 Human Reproduction

Human Reproduction NCERT Textbook Questions and Answers

Question 1.
Fill in die Blanks:

1. Humans reproduce …………………….. (asexually/ sexually)
2. Humans are …………………….. (oviparous, viviparous, ovoviviparous)
3. Fertilization is …………………….. in humans, (external / internal)
4. Male and female gametes are …………………….. (diploid / haploid)
5. Zygote is …………………….. (diploid / haploid)
6. The process of release of ovum from a mature follicle is called ……………………..
7. Ovulation is induced by a hormone called ……………………..
8. The fusion of male and female gametes is called ……………………..
9. Fertilisation takes place in ……………………..
10. Zygote divides to form …………………….. which is implanted in uterus.
11. The structure which provides vascular connection between fetus and uterus is called ……………………..

Answer:

1. Sexually
2. Viviparous
3. Internal
4. Haploid
5. Diploid
6. Ovulation
7. LH and FSH
8. Fertilisation
9. Follopian tube
10. Embryo
11. Placenta.

Question 2.
Draw a labelled diagram of male reproductive system.
Answer:

Question 3.
Draw a labelled diagram of female reproductive system.
Answer:

Question 4.
Write two major functions each of testis and ovary
Answer:
Functions of testis functions:

• Production of sperms by seminiferous tubules.
• Production of male sex hormone, testosterone by leydig cells.

Functions of Ovary

• Production of ova (eggs).
• Production of female sex harmones, estrogen and progesterone.

Question 5.
Describe the structure of a seminiferous tubuls.
Answer:
Seminiferous tubules are highly coiled tubes, which are lined on the inside by :

• Male germ cells called spematogonia that undergo meiotic division to form sperm celts.
• Sertoli cells provides nutrition and molecular signals to the germ cells.
  

Question 6.
What is spermatogenesis? Briefly describe the process of spermatogenesis.
Answer:
Spermatogenesis : Formation of sperms in the testis is called as spermatogenesis. It involves in the following steps :

1. Multiplication phase : In this phase, sperm cells are formed in testes.
The inner layer of seminiferous tubules of testes is formed of germinal epithelium.
Some of these cells called primary germ cells divide mitotically into spermatogo¬nia which become separated in the germi¬nal layer. Other cells of this layer serve as nutrition for the dividing cells.

2. Growth phase : In this phase, spermatogonia starts growing, absorbing nutrient substances. These large cells are called primary spermatocytes.

3. Maturation phase : It is a very important phase. Primary spermatocytes divide twice. The first division is meiotic due to which the number of chromosomes is reduced to half. In this process, primary spermatocyte divides into two halves which are known as secondary spermatocytes. The second division is mitotic and no change takes place in the number of chromosomes. Thus, from two secondary spermatocytes four spermatids are formed. In this manner from one primary spermatocyte four spermatids are formed. These spermatids change into sperm cells of spermatozoa by a process called metamorphosis.

Question 7.
Name the hormones involved in regulation of spermatogenesis.
Answer:
The hormones involved in regulation of spermatogenesis are:

• Gonadotropin releasing hormone
• Luteinizing hormone (LH)
• Follicle stimulating hormone
• Testosteron.

Question 8.
Define spcrmiogenesis and spermiation.
Answer:
Spermiogenesis : The process involving transformation of spermatid into spermatozoa is called spermiogenesis.
Spermiation: After spermiogenesis sperm heads became embedded in the sertoli cells and are finally released from the seminiferous tubules by the process called spermiation.

Question 9.
Draw a labelled diagram of human sperm and explain its defferent parts.
Answer:
Structure of sperm: A mature sperm is a delicate microscopic, motile structure. A typi¬cal mammalian sperm consists of the following three parts:

1. Head,
2. Middle piece and
3. Tail.

(1) Head: Head is knob like terminal part of the sperm. It is composed of a large nucleus and an acrosome. At die time of entry of the sperm into egg acrosome Secretes spermlysin which dis¬solve the egg membrane and thus facilitates entry of sperm into the egg or ovum.

(2) Middle Piece : It is short and lies be¬tween head and tail. It contains two granules called the proximal and distal centrioles in front side and towards posterior side cylindrical middle part of sperm. It is considered as the power house of sperm as it contains compact mass of mitochondria, which provides energy for metabolism and movement of sperm.

(3) Tail: It is situated on posterior part of sperm. It moves with the help of axial filament. The posterior part of the tail is called as end piece and it is not covered by membrane.

Question 10.
What are the major components of seminal plasma?
Answer:
The main components of the seminal plasma are fructose, calcium ion, some enzymes and prostagladines.

Question 11.
What are the major functions of male accessory ducts and glands?
Answer:
The main functions of male accessory ducts and glands are as follows :

1. Functions of accessory ducts:

(a) Rete Testis : They transport sperms from seminiferour tubule to Vas efferentia.
(b) Vas efferentia : Transports sperms to epdidymis.
(c) Epididymis : Sperms are stored here. Maturation of sperms occur.
(d) Vas deference : Transports sperms from epididymis to the urethra.

(2) Functions of glands:

(a) Prostate gland : It produces milky secretion which forms considerable part of the semen. It makes sperm motile.
(b) Bulbourethral gland : Its secretion make the penis lubricated.
(c) Seminal vesicle: It secrete mucus and watery alkaline fluid which provide energy to the sperm.

Question 12.
What is oogenesis ? Give a brief account of oogenesis. .
Answer:
Oogenesis is the process of formation of mature female gametes from primordial germ cells.

• This process is initiated during embryonic developmental stage when about two million gamete mother cells (oogonia) are formed in each foetal ovary.
• Oogonia start meiotic division which gets arrested at prophases-I stage. They are referred to as primary oocytes.
• Each of these gets covered with layers of granulose cells and are then called primary follicle.
• Many of the primary follicles degenerate from birth to puberty, leaving about 60000-80000 in each ovary at puberty.
• More layers of granulose cells and another theca layer surround it and now it is called secondary follicle. Theca layer is arranged as inner theca-intema and outer theca- extema.
• Secondary follicle transforms into tertiary follicle that has a fluid filled cavity called antrum.
• The primary oocyte within the tertiary follicle grows in size and completes its first meiotic division now.
• This is an unequal division resulting in the formation of:
  (a) A large haploid cell (that keeps the majority of nutrient rich cytoplasm) called secondary oocyte.
  (b) A tiny cell, with haploid nucleus and almost no cytoplasm called first polar
  body.
• The tertiary follicle undergoes certain changes to mature into graafian follicle.
  Secondary oocyte forms a new membrane around it, called zona pellucida.
• Under the influence of LH, the Graaffian follicle now ruptures to release secondary oocyte from the ovary by a process called ovulation.

Summary of oogenesis:

Oogonia Meiosis-I initiated -4 Primary oocyte (arrested at prophase-I) → Granu¬losa layer builds → Primary follicle → More granulose and theca layer added → Secondary follicle → Fluid filled cavity develops → Tertiary follicle → Primary oocyte completes meio- sis-I → Secondary oocyte (haploid)+ polar body → Tertiary follicle transforms to Graafian follicle → Zona pellucida builds around secondary oocyte Graafian follicle ruptures → Secondary oocyte (ovum) released.
Meiosis-II will occur only at the time of penetration of sperm into the ovum.

Question 13.
Draw a labelled diagram of a section through ovary.
Answer:

Question 14.
Draw a labelled diagram of a graafian follice.
Answer:

Question 15.
Name the function of the following:
(a) Corpus luteum
(b) Endometrium
(c) Acrosome
(d) Sperm tail
(e) Fimbriae.
Answer:
The functions of the following :
(a) Corpus luteum Secretes large amount of progesterone which is essential for the maintenance of endometrium of the uterus.
(b) Endometrium is necessary for the implantation of the fertillised ovum, for contrib¬uting towards making of placenta and other events of pregnancy.
(c) Acrosome is filled with enzymes that help in dissolving the outer cover of the ovum and entry of sperm nucleus.
(d) Sperm tail facilitates motility of the sperm essential for reaching the ovum to fertilise it.
(e) Fimbriae are fmgers-like projections at the mouth of fallopian tubules that help in
collection of the ovum after ovulation.

Question 16.
Identify true/ false statement to make it true.

1. Androgens are produced by sertoli cells. (True / False)
2. Spermatozoa get nutrition from sertoli cells. (True / False)
3. Leydig cells are found in ovaiy. (True / False)
4. Leydig cells synthesise androgens. (True / False)
5. Oogenesis takes place in corpus luteum. (True / False)
6. Menstrual cycle ceases during pregnancy. (True / False)
7. Presence or absence of hymen is not a reliable indicator of virginity or sexual experience. (True /False)

Answer:

1. Flase
2. True
3. False
4. True
5. False
6. True
7. True.

Question 17.
What is mentrual cycle? Which hormones regulate menstrual cycle?
Answer:
The reproductive cycle in the female primates is called menstrual cycle. The uterus linings becomes thick and spongy to receive fertilised egg. If the egg is not fertilised, this lining is not needed any longer so, it slowly breaks and comes out through vagina along with blood and mucous. This is called menstruation. It is repeated at an average interval of about 28/29 days.
Following hormones are regulate this cycle:

• Gonadotropin
• strogen
• Luteinizing hormone
• Follicular stimulating hormone
• Progesteron.

Question 18.
What is parturition? Which hormones are involved in induction of parturition?
Answer:
The process of delivery of the foetus (Child birth) at the end of the pregnancy is called parturition. The signals for parturition originate from the fully developed foetus and the placenta, which trigger the release of oxytocin from the maternal pitutary. Oxytocin acts on the uterine muscles and induces stronger uterine contractions leading to expulsion of the baby. Relaxin hormone released by the ovary widens the vagina to facilitate birth.
Following hormones are involved in induction of parturition:

1. Cartisol
2. Estrogen
3. oxytocin.

Question 19.
In our society the women are often blamed for giving bird) to daughters. Can you explain why this is not correct?
Answer:
Women are blamed for giving birth to daughters. This is wrong because sex of the baby is determined by the sperm that can have either X or Y-chromosome. Women have only one type of chromosome (X) in all the ova.
If the sperm having X-chromosome fertillises the ovum (X), the resulting zygote (XX) will become a female.
If the sperm having Y-chromosome fertillises the ovum (X), the resulting zygote (XY) will become a male.

Question 20.
How many eggs are released by a human ovary in a month? How many eggs do you think would have been released if the mother gave birth to identical twins? Would your answer change if the twins born were fraternal?
Answer:
Only one egg is released by a human (female) ovary in a month. Only one egg is released if the mother gave birth to identical twins. Yes two or more eggs are released in case fraternal twins are born.

Question 21.
How many eggs do you think were released by the ovay of the female dog which gave birth to 6 puppies?
Answer:
Six eggs are released by the ovary of a female dog if it gave birth to six puppies.

Human Reproduction Other Important Questions and Answers

Human Reproduction Objective Type Questions

1. Choose the Correct Answers:

Question 1.
Fertilization is related by: (CBSE PMT 2007)
(a) Realizing & gamete cells from gonad
(b) Transfer of male gametophy te to female gamete
(c) Fusion of male and female sex organs
(d) Fusion of nucleus of male gametes and nucleus of female gamete.
Answer:
(d) Fusion of nucleus of male gametes and nucleus of female gamete.

Question 2.
Cleavage is a process of fertilized egg, in which egg.
(a) Does not divide, but grows in sizes
(b) Divides continuously but does not grow in size
(c) Divided continuously and grows in size
(d) None of these.
Answer:
(b) Divides continuously but does not grow in size

Question 3.
Foetal membranes provide:
(a) Protection of embryo
(b) Nutrition to embryo
(c) Protection and nutrition to embryo
(d) None of these.
Answer:
(c) Protection and nutrition to embryo

Question 4.
Science of ageing is called:
(a) Chronology
(b) Odontology
(c) Gynecology
(d) Gerontology.
Answer:
(d) Gerontology.

Question 5.
The female counterpart of prostate gland in male (man) is:
(a) Bertholin’s gland
(b) Uterus
(c) Clitoris
(d) None of these
Answer:
(d) None of these

Question 6.
Humanis:
(a) Oviparous
(b) Viviparous
(c) Ovoviviparous
(d) None of these
Answer:
(b) Viviparous

Question 7.
Periodic cycle is:
(a) Of menstrual phase
(b) Of estrogen secretion
(c) Of fertilization
(d) None of these
Answer:
(a) Of menstrual phase

Question 8.
Ageing in mammals including man is due to:
(a) Adverse changes in environment
(b) Interaction between hereditary factors (genes) and the environment
(c) Malnutrition and stress
(d) All of these.
Answer:
(b) Interaction between hereditary factors (genes) and the environment

Question 9.
The part of the human body shows regeneration is:
(a) Spleen
(b) Kidney
(c) Brain
(d) Liver
Answer:
(d) Liver

Question 10.
Fertilization in mammals occurs in:
(a) Oviduct funnel
(b) Fallopian tubule
(c) Uterus
(d) Vagina.
Answer:
(b) Fallopian tubule

Question 11.
The capsule enclosing testes of mammal is called:
(a) Tunica albugenia
(b) Tunica membrana
(c) Tunica vaginalis
(d) Tunica vesculosa
Answer:
(a) Tunica albugenia

Question 12.
Sertoli cells are found in:
(a) Testes of Earthworm
(b) Testes of Frog
(c) Testes of Mammals
(d) Testes of Cockroach
Answer:
(a) Testes of Earthworm

Question 13.
The cavity of gastrula is known as:
(a) Blastocoel
(b) Coelome
(c) Archenteron
(d) Haemocoel
Answer:
(c) Archenteron

Question 14.
Implantation is the process in which
(a) Fertilization of egg
(b) Movemènt of egg
(c) Disappear of egg
(d) Blastosyst is formed by uterus.
Answer:
(a) Fertilization of egg

Question 15.
Seminiferous tubule is found in: ‘
(a) In testes
(b) In ovary
(c) In kidney
(d) In lungs.
Answer:
(a) In testes

2. Match the Following:

Answer:
1. (e)
2. (d)
3.(a)
4. (c)
5.(b).

Answer:

1. (b)
2. (c)
3. (d)
4. (e)
5. (a).

3. Answer in One Word/Sentence:

1. How many sperms will be produced from 24 spermatocytes during spermatogenesis ?
2. Where does fertilization takes place in mammals ? (SSCE1993, CBSE 95)
3. Write the name of various phases of embryogenesis.
4. How many polar bodies are formed during the formation of one gamete?
5. Write die name of three layers of gastrula.
6. How many polar bodies are formed during the formation of ovum during oogenesis? (CBSE 1993)
7. Name the substance formed in sperms and which helps the sperms to enter into ovum. (AISB1991)
8. How many sperms and ova are formed from 100 primary spermatocytes and primary oocyte respectively ? (SSCE 1992)
9. Name the part of sperm secreting enzyme for the entrance of sperms into ovum. (SSCE 1992)
10. Name the organ where corpus luteum is formed. (SSCE 1995)
11. Write the duration of gestation period in human cases.
12. How many autosomes are found in human sperm ?
13. Where is corpus luteum formed ?
14. Name the developmental stage of man in which it is transplanted of uterus wall.(SSCE 1993)
15. Name the process of release of ovum from graafian follicle.

Answer:

1. 96,
2. Fallopian tube
3. Cleavage
4. Blastula and Gastrula Infant, 4.3
5. Ectoderm, mesoderm and endodenn
6. 2
7. Spermlysin
8. 400,100
9. Head
10. Ovary
11. 240 days
12. 22
13. Ovary
14. Blastula
15. Ovulation.

Human Reproduction Very Short Answer Type Questions

Question 1.
By which term, the process of the formation of morulla from zygote is referred?
Answer:
Cleavage.

Question 2.
What is called first menstrual stage or phase in the girls age 12-14 years?
Answer:
Menarche.

Question 3.
What is the example of spermatogenesis?
Answer:
Male gametogenesis.

Question 4.
What provides nourishment to foetus inside the uterus?
Answer:
Placenta.

Question 5.
How many germinal layers are there in gastrula stage?
Answer:
Three.

Question 6.
By which term, the middle germinal layer of gastrula is referred?
Answer:
Mesoderm.

Question 7.
After Fertilization, how many days are needed for the birth of human child?
Answer:
280 days (9 months and 10 days).

Question 8.
To produce the new organisms of their own kind is called by a term, name it
Answer:
Reproduction.

Question 9.
By which name, the reproduction happens by means of fusion of two different gametes?
Answer:
Sexual reproduction.

Question 10.
Which gametogenesis goes on till life span in human beings after attaining puberty?
Answer:
Spermatogenesis.

Question 11.
The stoppage of menstrual cycle in a 50 yrs old female is known as.
Answer:
Menopause.

Question 12.
What is pregnancy?
Answer:
The time period between fertilization to the birth of child is called pregnancy.

Question 13.
Where is carpora cavernosa found?
Answer:
Carpora cavernosa is found in penis.

Question 14.
What is the gestation period in elephant, dog and cat ?
Answer:
Elephant 641 days dog 58-68 days, cat 63 days.

Question 15.
Name the hormone that relaxes public symphysis during parturition.
Answer:
Relax in hormone.

Human Reproduction Short Answer Type Questions

Question 1.
Explain menarchy or menopause.
Answer:
Menopause: In every human female, puberty period starts from 12-13 yrs of age to 45-50 yrs of the age. During this period except pregnancy at every interval of a month during 26th day to 28th day. If pregnancy does not occur then the internal wall of the uterus secretes out mucilaginous liquid along with blood. Secretion continues for 3-4 days called menses. As it comes at definite period so, it is called menstruation cycle. At the age of 40-50 yrs. menses stop and females reach to a stage called menopause. Ability pregnancy also stops after attaining menopause.

Question 2.
Draw a well labelled diagram of the T.S. of human testis.
Answer:

Question 3.
Draw a well labelled diagram of Oogenesis.
Answer:

Question 4.
What is the position of fallopian tubule in female reproductive organs? What are their significance ?
Answer:
Fallopian tubules are a pair of small muscular tubes, one each on either side ol*the uterus. These tubules extend from the vicinity of the ovary to the ovary. Each tubule is about 10 cm in length. The free end of each tube lies near the ovary of its side. This end is funnel shaped and fimbriated. It is called ostium and infundibulum. Infundibulum opens in the abdominal cavity by means of abdominal ostium. The fallopian tubule is kept in position by a mesentery which is attached to the uterus.

Significance of Function of Fallopian Tubes:

• By their lashing movement of the cilia present in the lining of infundibulum and nearby area help in pulling the released ovum into fallopian tube.
• Passage of ovum into uterus is aided by muscular movement of fallopian tube as well as beating of cilia present in the lining layer of tube.
• Fertilization of ovum mostly takes place in the ampulla part of fallopian tube.

Human Reproduction Long Answer Type Question

Question 1.
Write differences between spermatogenesis and oogenesis
Answer:
Differences between Spermatogenesis and Oogenesis:

Spermatogenesis	Oogenesis
1. Sperms are produced by this process.	1. Ovums are produced by this process.
2. In this process primary spermatocytes are formed by maturation of germinal epithelium cells.	2. In this process primary oocytes are formed by maturation of germinal epithelium.
3. Primary spermatocyte divides to form four spermatids.	3. Primary oocytes divides to form one ovum and three polar bodies.
4. There is equal division.	4. There is unequal division.
5. Large number of sperms are formed by this	5. Less number of ovums are formed by this process.

Question 2.
Describe the process of the formation and functions of corpus luteum.
Answer:
Corpus luteum is formed within ovary. It is a yellow body or structure which develops from ruptured Graafian follicle after the release of ovum. The cells become enlarged and conical. They are filled with a fluid called as luteum. It is developed under influence of L.H. of anterior pituitary. If fertilization do not occur it degenerates but if fertilization occurs, it remains for seven months during pregnancy and is responsible for the formation of some hormones which stimulates pregnancy and lactation.

Question 3.
Describe the structure and function of fallopian tubes.
Answer:
Fallopian tubules are a pair of small muscular tubes, one each on either side of the uterus. These tubules extend from the vicinity of the ovary to the ovary. Each tubule is about 10 cm in length. The free end of each tube lies near the ovary of its side. This end is funnel shaped and fimbriated. It is called ostium and infundibulum. Infundibulum opens in the abdominal cavity by means of abdominal ostium. The fallopian tubule is kept in position by a mesentery which is attached to the uterus.

Function of Fallopian Tubes:
By their lashing movement of the cilia present in the lining of infundi-bulum and nearby area help in pulling the released ovum into fallopian tube. ,
Passage of ovum into uterus is aided by muscular movement of fallopian tube as well as beating of cilia present in the lining layer of tube.
Fertilization of ovum mostly takes place in the ampulla part of fallopian tube.

Question 4.
In our society the women are often blamed for giving birth to daughters. Can you explain why this is not correct ?
Answer:
It is not correct to blame women for giving birth the daughters. The male sperm contains either X or Ychromosome whereas the female egg contains only x chromosomes. At the time of fertilisation when sperm carrying x chromosome combines with egg carring x chromosome of female Xygote z is formed which would be a female and when sperm with Y chromosome combines with egg containing X chromosome XY zygote is formed which would be a male. Thus scientifically sex of the baby is determined by the father and not by the mother as blamed in our society.

Question 5.
Describe the structure of ovary.
Answer:
These are a pair of female gonads or primary sex-organs lying one on each side of uterus. Ovary is attached to abdominal wall as well as uterus by means of ligaments. It is surrounded by a fold by peritoneum named mesovarium. Ovary is internally differentiated into four parts: germinal epithelium, tunica albuginea, cortex and medulla. Germinal epithelium is the outermost layer of cuboidal to flattened cells. Germinal epithelium is followed by a sheath of condensed connective tissues which is termed as tunica albuginea. It is followed by cortex. The central part of ovary contains medulla. A large number of groups of specialized cells are present in the cortex which are termed as ovarian follicles. These follicles are found in four development stages :

Incipient follicle : The central part of these follicles contain a large cell which is covered by smaller cells.
Primary follicle: These follicles are developed from incipient follicles.
Vascular follicle: It is formed from primary follicles. The oocyte of these follicle is covered by a many layered thick wall.

Graafian follicle: Mature ovarian follicle is termed as graafian follicle. It is covered by two sheaths derived from cortex. The follicle contains a single oocyte. A group of follicular cells surrounds the oocyte or ovum. It is called cumulus ovaricus. Another group produces membrane granulosa. Oocyte has two non-cellular membranes, inner vitelline membrane and outer zona peUucida.

Question 6.
Describe the process of fertilization and give its significance.
Answer:
Fertilization: Fertilization is the fusion of male and female gametes to produce a single diploid cell, called zygote. Fertilization in human female takes place in fallopian tube.

In a sexual mating or coitus the male ejaculates semen into the vaginal passage of the female using the copulatory organ, the penis. In a single coitus as many as 200 million sperms are introduced into the female genital tract but out of this huge number of sperms only one is destined to fuse with the ovum, provided the fallopian tube lodges of fully developed seqondary oocyte.Sperms travel through the vaginal passage and enter the uterus through the cervix.

They travel further through the uterus and finally enter the fallopian tube.The vaginal passage is highly acidic to prevent any bacterial infection but this acidic medium is not suitable for the survival of sperms. Many sperms die on the way. The liquid medium of the semen is alkaline which can neutralize the acidity of vagina to some extend and keep the. sperms alive and active. The sperms move with the speed of 1 -5 to 3 mm per minute.

The ovum gets surrounded by a large number of sperms but usually only one fuses with the ovum. The sperm penetrates the ovum using certain chemical substances of enzymatic nature.These chemicals are called spermlysins which are present in the acrosome. Certain receptors on the cell surface of the ovum enable the sperms to penetrate the wall of ovum. The ovum is surrounded by follicle cells. These cells are joined together by a glue like substance known as mucopolysaccharide, an acid, called hyaluronic acid. The sperm pro¬duces spermlysin, known as hyaluronidase. The over all changes in a sperm before the fertilization is called capacitation.

The hyaluronidase enzyme facilitates the sperm to pen¬etrate through the corona radiata (follicle cells), zona pellucida and the plasma membrane of ovum. The nucleus and the cytoplasmic components get inside the ovum, leaving the tail outside. The entry of sperm stimulates the ovum and the signal is transmitted to the egg surface incapacitating all the other cells surrounding the ovum. Nucleus of sperm move towards the nucleus of ovum and they fuses with each other to form zygote. It takes 2 \(\frac { 1 }{ 2 }\) hours to complete fertilization process. Once the ovum has been fertilized a barrier forms around it that normally prevents other sperms from entering.

Now fertilized egg reaches to the uterus and within seven days of fertilization it is transplanted to the wall of the uterus.

Significance of Fertilization
Egg become active after entry of sperm and completes its second maturation division.
Formation of fertilization membrane prevent entry of other sperms in the ovum. In human this membrane is not formed.
It restores the diploid number (2n) of chromosomes in the zygote.
It combines characters of male and female resulting in the introduction of variations. These variations make the offspring better equipped for struggle against environmental conditions to ensure the existence.
The ovum is stimulated to cleavage.
After fertilization ovum rotate inside the membrane.
Ovum do not contain centriole and obtain it from sperm during this process thus zygote continuously divides.
It is necessary for the egg to attain maturity.

Question 7.
Describe development of embryo up to the formation of three germ layer. Give the names of organs formed by three germ layer.
Or
Define cleavage. Describe the changes that occur in embryo till gastrulation.
Answer:
The term cleavage refers to a series of rapid mitotic divisions of the zygote following fertilization forming a many celled blastula. Following are the various steps of embryonic development in human up to the formation of three germ layer:

1. Formation of morula : The fertilized zygote divides. It undergoes successive quick mitotic cell divisions called cleavage. First cleavage is holoblastic, unequal and meridional. It divides the ovum completely into two unequal blastomeres. The plane of cleavage passes through animal vegetal axis, i.e., it is meridional. Large blastomere divides little earlier than the small one giving a transitional three cell stage. As a result of further cleavages, a solid mass of mulberry-shaped embryo is formed called morula.
Morula is of the size of zygote but consists of 32 cells. These cells are of two types : The outer layer of smaller cells around, inner larger cells. Within 72 hours of fertilization, morula reaches the uterus.

2. Formation of blastula : Transformation of morula into a blastula starts by the rearrangement of blastomeres. This leads to the formation of a central cavity inside the morula. The outer cells of morula absorb the nutritive fluid secreted by the uterine mjueous membrane and transform into trophoblast. The fluid absorbed by these cells collects in the central cavity called blastocoel. This cavity separates the trophoblast from the inner mass of larger cells except on one side and is termed blastocyst. The inner cell mass is pushed to one pole as a small knob. This knob gives rise to the embryo and is termed as embryonal knob.

3. Formation of gastrula : In this embryonic stage development of three germ layer occurs. In this stage morphogenic movement of cells of embryo occurs, as a result of this three germ layers are formed. A cavity develops at the centre called as archenteron which open outside through blastopore.

4. Formation of three germ layers :

Formation of endoderm : The enlargement of blastodermic vesicle is followed by the separation of few cells from the inner cell mass. These cells push out from the blastocoel to become the initial cells of the innermost layer of gastrula, the pattern of a tube within a tube. The inner tube is called primitive gut. It is differentiated into gut tract which is within the body and a yolk sac that communicates with the gut of the embryo. The remaining cells of the inner Cell mass are organized to form the embryonic disc.

Formation of mesoderm : After the formation of endoderm an increased rate of cell proliferation takes place at the caudal end of the embryonic disc. This results in the localised increase in the thickness of the disc. These cells subsequently get detached from the embryonic disc and get organized to a well demarcated mesodermal layer.
Formation of ectoderm: After the formation of endoderm and mesoderm, the remain¬ing cells of the embryonic disc arrange themselves in a layer to form ectoderm.

Fate of three germinal layer : Three germ layers differentiated at the time of gastrula- tion give rise to all the tissues and organs of the body of adult by the process of differentia¬tion and organogenesis.
Germ layers

1. Germ layers : Ectoderm
Tissue or organs of adult :

• Epidermis and its derivatives.
• Cutaneous sensory organs.
• Olfactory organs.
• Lens of eye.
• Membranous labyrinth (internal ear).
• Anterior lobe of pituitary gland.
• Lining of buccal cavity.
• Enamel of teeth.
• Endoderm
• Lining of proctodaeum.
• Brain, spinal cord, spinal and cranial nerves.

2. Germ layer : Endoderm
Tissue or organs of adult :

• Lining of alimentary canal except buccal cavity and rectum.
• Lining of larynx, trachea and lungs.
• Urinary bladder.
• Parathyroid, thyroid and thymus.
• Liver and pancreas.

3. Germ layer : Mesoderm
Tissue or organs of adult :

• Dermis.
• Vertebral column.
• Muscles of the body.
• Excretory organs.
• Reproductive tracts.
• Peritoneum.
• Circulatory system, heart, blood vessels, blood, lymph and spleen.

MP Board Class 12th Biology Solutions

MP Board Class 12th Chemistry Solutions Chapter 5 Surface Chemistry

Surface Chemistry NCERT Intext Exercises

Question 1.
Why are substance like platinum and palladium used for carrying electrolysis of aqueous solutions ?
Answer:
These metals are not attacked by the ions of the electrolytes or the products of electrolysis. Electrodes of such metals are called inert electrodes.

Question 2.
Why does physisorption decreases with the increase of temperature ?
Answer:
It is an exothermic process

Thus, when temperature is raised, reaction proceeds in backward direction and gas adsorbed gets released. It is accordance to Le-Chatelier’s principle.

Question 3.
Why are powdered substances more effective adsorbent than their crystal line forms ?
Answer:
Powdered form has greater surface area. Greater the surface area, greater is the adsorption.

Question 4.
Why is it necessary to remove CO when ammonia is obtained by Haber’s process ?
Answer:
For the preparation of ammonia in Haber’s process solid catalyst is used. It is necessary to remove the CO produced because the gas reacts with iron and forms Fe(CO)₅ which exist in liquid state at the temperature of the chamber and obstructs in the production of NH₃ because at high temperature CO and H₂ react by which production of ammonia decreases.
In short CO acts as poison for the iron catalyst used in the process. It is therefore, necessary to remove CO.

Question 5.
Why is the ester hydrolysis slow in the beginning and becomes faster after sometime ?
Answer:
CH₃COOC₂H₅ + H₂O → CH₃COOH + C₂H₅OH
Infact, this reaction is catalysed by an acid (H+). Acetic acid formed during the reac¬tion catalyses the hydrolysis of ester. Therefore, reaction becomes fast. It is called autocatalyst.

Question 6.
What is the role of desorption in the process of catalysis ?
Answer:
The product formed leaves the surface of catalyst and makes it available for adsorption of mole reactants molecules.

Question 7.
What modifications can you suggest in the Hardy-Schulze law ?
Answer:
The coagulating ion has charge opposite to that on the colloidal particles. Thus, when coagulating ion is added to colloidal solution, the change on colloidal particle is neutralised and coagulation occurs. According to Hardy-Schulze rule, greater the volume of the oppositely charged ions of the electrolyte faster is the coagulation the Hardy-Schulze law, consider the coagulation of colloidal sols because of neutralisation of charge on colloidal particles. We know that neutralisation and coagulation also takes place by mixing two oppositely charged colloidal solutions.

Thus, Hardy-Schulze law should also include the following when oppositely charged sols are mixed in right proportions, they neutralize charges of each other and undergo coagulation.

Question 8.
Why is it essential to wash the precipitate with water before estimating it quantitatively ?
Answer:
Some amount of impurities remains adsorbed on the surface of the precipitate. It is essential to remove the sticking impurities by washing with water.

Surface Chemistry NCERT TextBook Exercises

Question 1.
Distinguish between the meaning of the terms adsorption and absorption.
Answer:
Differences between Adsorption and Absorption :

Adsorption:

1. It is a process as a result of which one substance get concentrated only on the surface of the other.
2. Concentration of adsorbate on the surface of adsorbent is different than in the bulk.
3. It is a surface phenomenon.
   Example : Adsorption of water vapour on silica gel.

Absorption:

1. It is a process as a result of which one substance gets uniformly distributed in the volume of the other.
2. Concentration is uniform in the entire solid system.
3. It is a bulk phenomenon.
   Example : Adsorption of water vapour by dry calcium chloride.

Question 2.
What is the difference between physisorption and chemisorption ?
Answer:
Differences between Physical adsorption and Chemical adsorption :

Physical adsorption:

1. Low value of enthalpy of adsorption (20-40 kJ mol^-1)
2. This type of adsorption involves weak vanderWaals’ forces between adsorbent and adsorbate.
3. Usually takes place at low temperature and decreases with increase in temperature.
4. It is reversible in nature.
5. The extent of adsorption is approximately related to the case of liquification of the gas.
6. Forms multimolecular layers.
7. On increasing pressure, adsorption also increases.

Chemical adsorption:

1. High value of enthalpy of adsorption (40-400kJmol^-1 ).
2. This type of adsorption involves strong forces of attraction due to chemical bond formation.
3. Takes place at high temperature.
4. It is irreversible.
5. No such correlation.
6. Forms monomolecular layers.
7. No any effect of pressure.

Question 3.
Give reason why a finely divided substance is more effective as an adsorbent ?
Answer:
With the increase in surface area of adsorbent adsorption increases. Thus, in powdered state (finely divided substance) or in porous state surface area of metals is more. Therefore, adsorption is more in these states.

Question 4.
What are the factors which influence the adsorption of a gas on a solid ?
Answer:
Factors which affect the adsorption of gas on a solid are as follows :

1. Nature of gas
2. Surface area of adsorbent
3. Pressure
4. Temperature
5. Activity of adsorbent.

Question 5.
What is an adsorption isotherm ? Describe Freundlich adsorption isotherm.
Answer:
The graph showing the extent of adsorption versus pressure at constant tempera¬ture is known as adsorption isotherm. Adsorption isotherm graphs are of two types :
(a) Freundlich isotherm graph.
(b) Langmuir isotherm graph.

Freundlich isotherm: Freundlich gave an experimental relation between the amount of gas adsorbed by unit mass of adsorbent with pressure at a definite temperature. This relation can be represented by the following equation :
\(\frac{x}{m}=\mathrm{K.P}^{1 / n}(n>1)\) …..(1)
Where m is the mass of gas adsorbed on adsorbent x at pressure P, K and n are con¬stants which depend on the nature of adsorbent and gas at a definite temperature.
These graphs indicate at the definite pressure, physical adsorption decreases with the increase in temperature.
Taking log of equation (1)
log \(\frac { x }{ m } \) = log K + \(\frac { 1 }{ n } \) log P …..(2)
When a graph is drawn by taking log \(\frac { x }{ m } \) on y-axis and log P on x-axis, a straight line is obtained. This verifies Freundlich isotherm.
Slope = \(\frac { 1 }{ n } \) and intercept on y-axis = log K
value of \(\frac { 1 }{ n } \) can be between 0 and 1, thus eqn. (2)

can be applicable only upto a limited extention of pressure.
(i) When \(\frac { 1 }{ n } \) = 0, \(\frac { x }{ m } \) = constant, then adsorption is independent of pressure.
(ii) When \(\frac { 1 }{ n } \) = 1, \(\frac { x }{ m } \) = Kp, \(\frac { x }{ m } \) α P, then change in adsorption is proportional to pressure.

Question 6.
What do you understand by activation of adsorbent ? How is it achieved ?
Answer:
It means increasing the adsorption power of an adsorbent; it is done (i) by increasing the surface area, (ii) by making the surface rough, (iii) by removing the gas already adsorbed.

Question 7.
What role does adsorption play in heterogeneous catalysis ?
Answer:
In heterogeneous catalysis, the reactants are generally gases while catalysts are solids. The reactant molecules are adsorbed on the surface of solid catalyst by physical adsorption or chemical adsorption. As a result, the concentration of the reactant molecules on the surface of the catalyst increases and hence the rate of reaction also increases.

Question 8.
Why is adsorption always exothermic ?
Answer:
Adsorption leads to decrease in disorder, thus ∆S = +ve. For the process to be performed value of ∆G should be -ve. Thus, in equation ∆G = ∆H – T∆S, ∆G will be negative when ∆H will be negative i.e., exothermic. Thus, adsorption is an exothermic process.

Question 9.
How are the colloidal solutions classified on the basis of physical states of the dispersed phase and dispersion medium ?
Answer:
Classification on the basis of physical state of dispersed phase and dispersion medium : Depending upon the physical state of dispersed phase and dispersion medium whether these are solids, liquids or gases, eight types of colloidal systems are possible. The examples of the various types of colloids and their typical names are given in Table.

It may be noted that a gas mixed with another gas forms a homogeneous mixture and therefore it is not a colloidal system.

Different Types of Colloidal Systems

S.No.	Dispersed phase	Dispersion medium	System name	Example
1.	Solid	Solid	Solid sol	Some coloured glasses, gemstone.
2.	Solid	Liquid	Sol	Gold or silver sol, muddy water, paint, cell fluids.
3.	Solid	Gas	Aerosol of solid	Smoke, dust.
4.	Liquid	Solid	Gel	Jelly, curd, cheese
5.	Liquid	Liquid	Emulsion	Milk, hair cream
6.	Liquid	Gas	Aerosol of liquid	Fog, cloud, mist, insecticide spray.
7.	Gas	Solid	Solid foam	Pumice-stone, foam, rubber cork
8.	Gas	Liquid	Foam or froth	Froth, whipped cream, soap lather.

Out of the different types of colloids, the most common are sols (solid in liquids), gels (liquid in solids) and emulsions (liquid in liquid).

Question 10.
Discuss the effect of pressure and temperature on the adsorption of gases on solids.
Answer:
Effect of pressure: Adsorption is a reversible process and is accompanied by a decrease in pressure. Therefore, adsorption increases with an increase in pressure.
Effect of temperature: Adsorption is an exothermic process. Thus, in accordance with Le-Chatelier’s principle the mangnitude of adsorption decreases with an increase in temperature.

Question 11.
What are lyophilic and lyophobic sols ? Give one example of each type. Why are hydrophobic sols easily coagulated ?
Answer:
Lyophilic sols : Those sols in which there are forces of attraction between dispersed phase and dispersion medium, are called lyophilic sols. Lyophilic means liquid loving. They are directly prepared by mixing substances like gum, gelatine, starch with suitable dispersion medium like water, e.g., starch in water, albumin in water. They are reversible sols.

Lyophobic sols : The word ‘lyophobic’ means liquid hating. Substances like metals, their sulphides etc. when mixed with dispersion medium, do not form sols. They are prepared by special methods, e.g., Gold sol, As2S3 sol etc. In these sols, the particles of disperesed r phase have no affinity for dispersion medium and they are irreversible sols.

Reasons for coagulation of lyophobic sols : Lyophobic sols are easily precipited or coagulated on addition of small amounts of electrolytes, by heating or by shaking because they are not stable due to less force of attraction between dispersed phase and dispersion medium.

Question 12.
What is the difference between multimolecular and macromolecular col-loids ? Give one example of each. How are associated colloids different from these two types of colloids ?
Answer:
(i) Multimolecular colloids: In this type of colloids the colloidal particles consist of aggregates of atoms or small molecules with diameter of less than 1 nm. For example, a gold sol may contain particles of different sizes having several atoms of gold. Similarly sulphur sol contains about one thousand of S₈ molecules. These are held together by van der Waals’ forces.

(ii) Macromolecular colloids : In macromolecular colloids the dispersed particles themselves are big molecules, usually polymers. The molecular masses of these macro molecules range from thousands to millions. Synthetic compounds e.g. polyethylene, polystrene, nylon, rubber etc. are macromolecules. Since these molecules have dimensions comparable to those of colloidal particles, there dispersions are known as macromolecular colloids. Most lyophillic sols are of this category.

(iii) Associated colloids (Micelles): There are certain substances which behave as normal, strong electrolytes at low concentration, but exhibit colloidal properties at higher concentrations due to the formation of aggregated particles. These are called Micelles. These substances are also called Associated Colloids. Surface active agepts like soaps and detergents are of this class.

Question 13.
What are enzymes ? Write in brief the mechanism of anzyme catalysis.
Answer:
Enzymes are complex nitrogeneous organic compounds present in living beings. Enzymes catalyse many biochemical reactions taking place inside the human body like digestion, i.e., why enzymes are also called biocatalysts. For example,

Inversion of cane sugar is catalysed by invertase.

Mechanism of enzyme catalysis : There are present a number of cavities of characteristic shape on the surface of enzymes. The molecules of the reactant (substrate) which have complementary shape, fit into these cavities just as a key fits into a lock. An activated enzyme-substrate complex is formed which then decomposes to yield products. It involves following steps :

Step-I → Binding enzyme to substrate (reactant) to form a complex.

Step-II → Product formation from the complex

Step-III → Release of the product from the enzyme product complex.

Question 14.
How are colloids classified on the basis of:
(i) Physical states of components
(ii) Nature of dispersion medium and
(iii) Interaction between dispersed phase and dispersion medium ?
Solution:
Colloids can be classified on various bases as :
(i) On the basis of the physical state of the components (by components we mean the dispersed phase and dispersion medium). Depending on whether the components are solids, liquids, or gases, we can have eight types of colloids.
(ii) On the basis of the dispersion medium, sols can be divided as :

No.	Dispersion medium	Name of sol
1.	Water	Aquasol or hydrosol
2.	Alcohol	AIcosol
3.	Benzene	Benzeosol
4.	Gases	Aerosol

(iii) On the basis of the nature of the interaction between the dispersed phase and dispersion medium, the colloids can be classified as lyophilic (solvent attracting) and lyophobic (solvent repelling).

Question 15.
Explain, what is observed :
(i) When a beam of light is passed through a colloidal sol ?
(ii) An electrolyte, NaCl is added to hydrated ferric oxide sol ?
(iii) Electric current is passed through a colloidal sol ?
Answer:
(i) Scattering of light by colloidal particles takes place and path of the light becomes visible (Tyndall effect).
(ii) The positively charged colloidal particles of Fe(OH)₃ get coagulated by the oppositely charged Cl^– ions provided by NaCl.
(iii) On passing.electric current, the colloidal particles move towards the oppositely charged electrode where, they lose their charge and get coagulated. This is electrophoresis process.

Question 16.
What are emulsions ? What are their different types ? Give examples of each type.
Answer:
The colloidal system in which dispersed phase and dispersion medium both are liquid, is called emulsion.

Types of emulsions:
1. Oil in Water type (O/W) : In this type of emulsion small droplets of oil are dispersed in the water or dispersion medium, e.g., Milk, vanishing cream.

2. Water in Oil (W/O): In this type of emulsion, small quantity of water is dispersed in the form of droplets in oil (dispersion medium), e.g., Butter, Cod-liver.

Question 17.
What is demulsification ? Name two demulsifiers.
Answer:
The process of separation of constituent liquids of an emulsion is called demulsification. Demulsification can be done by centrifuging or boiling.

Question 18.
Action of soap is due to Emulsification or formation of micelle formation. Comment
Answer:
Cleaning action of soaps: Cleaning action of soap and detergents are based on miceller activity. Soaps are sodium salt of higher fatty acids e.g., sodium stearate which ionises as:

The anionic head of stearate ion (-COO^–) is hydrophilic and hence has great affinity for water. The hydrocarbon part is hydrophobic and has great affinity for oil, grease etc.

When soap dissolves in water the anions (C₁₇H₃₅COO^–) form micelle encapsulating oil or grease inside. These micelles are removed by rinsing with water. Thus the main function of soap is to convert oily and greasy dirt to colloidal particles by forming an emulsion. Soaps therefore, act as emulsifying agents. This mechanism of cleaning is also applicable to synthetic detergents like sodium lauryl sulphate CH₃(CH₂)₁₁ SO^–₄ Na⁺. Repulsion of similar charge -COO^– or -SO^–₄ covering each oil (grease) micelle prevents them to come together. Thus oil or grease remains in the suspension.

Question 19.
Give four examples of heterogeneous catalysis.
Answer:
Four examples of heterogeneous catalysis: (i) Oxidation of sulphur dioxide to form sulphur trioxide. In this reaction, Pt acts as catalyst.

(ii) Formation of ammonia by the combination of dinitrogen and dihydrogen in the presence of finely divided iron.

This process is called the Haber’s process.
(iii) Ostwald’s process : Oxidation of ammonia to nitric oxide in the presence of platinum.

(iv) Hydrogenation of vegetable is in the presence of Ni.

Question 20.
What do you mean by activity and selectivity of catalysts ?
Answer:
(a) Activity of a catalyst: The activity of a catalyst is its ability to increase the rate of a particular reaction. Chemisorptions is the main factor in deciding the activity of a catalyst. The adsorption of reactants on the catalyst surface should be neither too strong nor too weak. It should just be strong enough to make the catalyst active.
(b) Selectivity of the catalyst: The abilitiy of the catalyst to direct a reaction to yield a particular product is referred to as the selectivity of the catalyst. For example, by using different catalyst, we can get different products for the reaction between H₂ and CO.

Question 21.
Describe some features of catalysis by zeolites.
Answer:

1. Zeolites are hydrated alumino-silicates. They have three-dimensional network structure. They contain water molecules in their pores,
2. Zeolites are heated to remove water of hydration. The pores become vacant and zeolites are ready to act as catalyst.
3. The size of the pores varies from 260 pm to 760 pm. This shows that only those molecules can be adsorbed in these pores whose size is small enough to enter these pores. Thus, zeolites as molecular sieve and the shape selective catalysts.

Question 22.
What is shape selective catalysis ?
Answer:
A catalyst reaction is very specific, which depends upon the pore structure of the catalyst and on the size of the reactant and the product. Molecules is called shape-selective catalysis. For example: catalyst by zeolite is shape-selective catalysis.The pore size present in the zeolite ranges from 260-740 pm. Molecules having a pore size more than this cannot enter the zeolite and undergo the reaction.

Question 23.
Explain the following terms :
(i) Electrophoresis
(ii) Coagulation
(iii) Dialysis
(iv) Tyndall effect.
Answer:
(i) Electrophoresis : Colloidal particles are either positively charged or negatively charged. When this colloidal solution is put in electric field, colloidal particles move towards the electrodes of opposite charge and on reaching there deposited and get precipitated As, AS2S3 particles being negatively charged move towards anode and precipitated there.

The movement of colloidal particles towards the electrodes of opposite charge is called electrophoresis.This electrophoresis is also known as cataphoresis and anaphoresis depending upon movement towards cathode and anode respectively.

(ii) Coagulation : Colloidal particles are either positively charged or negatively charged. It is seen that on adding some oppositely charged ions or electrolyte, which cancels the charge of colloidal particles and these particles aggregate and change into precipitates. Precipitation of colloidal particles by electrolytes is called coagulation.

(iii) Dialysis: The process of separating impurity of crystalloids from colloidal sol by means of diffusion of the former through an animal or vegetable membrane, placed in running water, is called dialysis and the apparatus used for effecting such separation is called dialyser.

Graham’s dialyser consist [See Fig] of a parchment (or cellophone or cellulose acetate) bag, half immersed in water. The impure colloidal solution (i.e., a mixture of colloidal solution and crystalloids) is placed in the dialyser and the outside water is continuously renewed. The crystalloids slowly pass freely through the membrane into outside water, while pure colloidal solution is left inside the dialyser. This is, however, a very slow process. By allowing the process to continue over a period and pumping fresh water continually into the container, most the ions are eventually removed and the sols get purified. The membrane used is called semipermeable membrane, because it allows selectively the passage of only crystalloids particle and not colloidal particles.

(iv) Tyndall effect: In 1869 Tyndall noted that when a beam of light passes through colloidal solution, in a dark place, path of light is illu¬minated by bluish light. Colloidal particles scatter light and due to this scattering the light path, way is seen like a bright cone.

This effect is known as Tyndall effect. The same phenomenon is observed when a beam of sunlight passes through a small slit or hole in a dark room. This cone is perpendicular to light path.

Question 24.
Give four uses of emulsions.
Answer:
Applications or uses of emulsion :

1. Cleaning action of soaps and detergents are based on emulsification.
2. Emulsions are used as medicines e.g., codliver oil.
3. Many disinfectants like phenyl, dettol, lysol etc., are when mixed with water, form emulsions like oil.
4. Froth floatation process for concentration of ore is based on the principle of emulsification.
5. Digestion of fat by intestine also involves emulsification.

Question 25.
Explain the terms with suitable examples :
(i) Alcosol
(ii) Aerosol
(iii) Hydrosol.
Answer:
(i) Alcosol: It is a colloidal solution in which alcohol is the dispersion medium. For example, colloids which has cellulose nitrate as dispersed phase and ethyl alcohol as dispersion medium.
(ii) Aerosol: It is a colloidal solution in which liquid is a dispersed phase and gas is a dispersion medium e.g., fog, mist, cloud etc..
(iii) Hydrosol: It is a colloidal solution in which solid is a dispersed phase and water is a dispersion, e.g., gold sol, arsenious sulphide sol, ferric oxide sol etc.

Question 27.
Comment on the statement that “Colloid is not a substance but a state of substance”.
Answer:
The given statement is true. It is because colloidal is not the property of substance. Colloidal is a state in which all the substance can be brought by suitable methods. If the size of the particle lies in the range 1 nm to 1000 nm, it is in the colloidal state.

Surface Chemistry Other Important Questions and Answers

Surface Chemistry Objective Type Questions

Question 1.
Choose the correct answer :

Question 1.
In the adsorption process of acetic acid on activated charcoal, acetic acid is :
(a) Adsorber
(b) Absorber
(c) Adsorbent
(d) Adsorbate.

Question 2.
Cause of stability of lyophobic sol is :
(a) Brownian movement
(b) Tyndall effect
(c) Electric charge
(d) Brownian movement and Electric charge.

Question 3.
In the coagulation of As₂S₃ colloidal solution value of whose coagulating power will be minimum:
(a) NaCl
(b) KCl
(c) BaCl₂
(d) AlCl₃.

Question 4.
Adsorption process is :
(a) Endothermic
(b) Exothermic
(c) No heat change
(d) None of these.

Question 5.
Size of colloidal particles in the range of:
(a) 10^-7 to 10^-9 cm
(b) 10^-9 to 10^-1 cm
(c) 10^-5 to 10^-7 cm
(d) 10^-2 to 10^-8 cm.

Question 6.
Which of the following is not used for the preparation of lyophilic colloid :
(a) Starch
(b) Gum
(c) Gelatin
(d) Metal sulphide.

Question 7.
Sol which can act like a protective colloid :
(a) As₂S₃
(b) Gelatin
(c) Au
(d) Fe(OH)₃

Question 8.
Fog is an example of colloidal system of:
(a) Liquid dispersed in gas
(b) Gas dispersed in gas
(c) Solid dispersed in gas
(d) Solid dispersed in liquid.

Question 9.
Gelatin is mostly used in making ice creams in order to :
(a) Prevent forming a colloidal sol.
(b) Enrich the fragrance
(c) Prevent crystallization and stabilize the mixture
(d) Modify the taste.

Question 10.
In the reaction

(a) Auto catalyst
(b) Poison
(c) Negative catalyst
(d) Positive catalyst.

Question 11.
The migration of colloidal particles under the influence of electric fields is :
(a) Cataphoresis
(b) Electrodialysis
(c) Electrophoresis
(d) Electrical dispersion.

Question 12.
Hardy-Schulze law is related with :
(a) Solution
(b) Coagulation
(c) Solids
(d) Gases.

Question 13.
How many phases are present in a colloidal solution :
(a) 1
(b) 2
(c) 3
(d) 4.

Question 14.
Which is an emulsion among the following :
(a) Air
(b)Wood
(c) Butter
(d) Milk.

Question 15.
Butter is:
(a) A gel
(b) An emulsion
(c) A sol
(d) Not a form of colloid.

Question 16.
Sol which acts as protective colloid is :
(a) Gelatin
(b) Au
(c) As₂S₃
(d) Fe(OH)₂

Question 17.
Which is not correct for physisorption :
(a) A reversible process
(b) Needs low heat of adsorption
(c) Needs activation energy
(d) Needs low temperature.

Question 18.
In which among the following is Tyndall effect not expected :
(a) Suspension
(b) Emulsion
(c) Sugar solution
(d) Gold sol.

Answers:

1. (d), 2. (d), 3. (d), 4. (b), 5. (c), 6. (d), 7. (b), 8. (a), 9. (c), 10. (b), 11. (c), 12. (b), 13. (b), 14. (d), 15. (a), 16. (a), 17. (c), 18. (c).

Question 2.
Fill in the blanks :

1. Rate of physical adsorption ………………………… with the increase in temperature.
2. Particles of As₂S₃ sol are …………………………
3. In the contact process of manufacture of H₂SO₄ for Pt catalyst ………………………… act as …………………………
4. Oxidation of oxalic acid by KMnO₄ is an example of …………………………
5. Biological catalysts are necessarily …………………………
6. Movement of colloidal particles under the effect of electric field is called …………………………
7. Scattering of light by colloidal particles is called ………………………… effect|
8. Intermediate compound theory is applicable to ………………………… catalyst
9. The substance on whose surface adsorption takes place is called an …………………………
10. Milk is an example of …………………………
11. Blood is a ………………………… charged colloid.
12. Adsorption is an ………………………… process.
13. Colloidal solution of solid in liquid is called …………………………
14. Catalytic promoter substance is …………………………
15. On adding electrolyte, precipitation of colloidal particles is known as …………………………
16. According to Hardy Schulze law, coagulating capacity of ions depend on the ………………………… of ions

Answers:

1. Decreases
2. Negatively charged
3. As₂O₃, poison
4. Auto catalysis
5. Enzyme
6. Electrophoresis
7. Tyndall effect
8. Homogeneous
9. Adsorbent
10. Emulsion
11. Negatively
12. Exothermic
13. Gel
14. Molybdenum
15. Coagulation
16. Charge.

Question 3.
Match the following :

I.

Answers:

1. (f)
2. (d)
3. (a)
4. (c)
5. (g)
6. (e)
7. (b).

II.

Answers:

1. (d)
2. (a)
3. (b)
4. (e)
5. (c)
6. (f)
7. (g).

Question 4.
Answer in one word/sentence :

1. What happen when gelatin is mixed into gold sol ?
2. The substance which increases the strength of the catalyst but do not work as catalyst.
3. Dissociation of emulsion into its constituent liquid is known as :
4. The catalyst which is used for hydrogenation of oils ?
5. The decomposition of hydrogen peroxide by phosphoric acid represents which kinds of catalysis ?
6. Which catalyst converts glucose into alcohol ?
7. Among Na⁺, Ba⁺², Al⁺³, Sn⁺⁴ ions which one has the strongest coagulation power ?
8. Cl₂ gas mask works on which principle ?
9. Conversion of a precipitate into colloidal particles is known as:
10. Cleansing action of soap based on which principle ?
11. Who used the word catalyst for the first time ?
12. Write the size of colloidal particles.
13. Write nature of catalyst used in oxidation of oxalic acid by KMnO₄.
14. Give an example of catalytic poisoning.
15. Movement of particles of colloids is called.
16. Which one catalyst is used for hydrolysis of cane sugar.

Answer:

1. Protection
2. Catalyst promotor
3. Demulsification
4. Ni
5. Negative catalyst
6. Zymase
7. Sn⁺⁴
8. Adsorption
9. Peptization
10. Emulsification
11. Bergellius
12. 10^-5 to 10^-7 cm
13. Auto catalyst
14. As₂O₃ in contact process
15. Brownian motion
16. Invertase enzyme.

Surface Chemistry Very Short Answer Type Questions

Question 1.
Which inert gas is adsorbed in (i) Minimum amount and (ii) Maximum amount on the surface of gas charcoal ?
Answer:

1. Helium because of its lower atomic mass and the weakest van der Waals’ forces of attraction is adsorbed on gas charcoal in minimum amount.
2. Xenon because of its high atomic mass and the strongest van der Waals’ forces of attraction is adsorbed on gas charcoal in maximum amount.

Question 2.
Why is sky blue in colour ?
Answer:
Dust particles present in air forms colloidal solution whose particles shows Tyndall effect and hence sky appears blue in colour.

Question 3.
KMnO₄ decolourises slowly initially and then rapidly when added to oxalic acid. Why ?
Answer:
Addition of KMnO₄ to oxalic acid oxidises it. Mn⁺² ion produced in this reaction acts as autocatalyst and hence decolourisation occur rapidly.
2MnO^–₄ + 5C₂O^-2₄ + 16H^– → 2Mn⁺² + 10CO₂ + 8H₂O

Question 4.
What is Colloidal solution ?
Answer:
The heterogeneous solution in which solute particles of 10^-7 cm to 10^-4 cm diameter and solvent particles are within 10^-8 cm to 10^-7 cm are called colloidal solution.
e.g. Milk, blood, cloud, smoke, etc.

Question 5.
What is adsorbent ?
Answer:
Solid substances which adsorb the gases or solution are called adsorbent. Like : animal charcoal, silica etc.

Question 6.
What are adsorbate ?
Answer:
Gas molecules, vapours or ions which are adsorbed on the surface of solids are called adsorbate.

Question 7.
Delta is formed when river water meets sea water. Explain.
Answer:
In the river water negatively charged particles of soil and sand are present. When river water meets sea-water, various ions Na⁺, K⁺ or Mg⁺⁺ present in sea water causes coagulation and soil particles etc. are settle down. Thus a delta is formed.

Question 8.
How is rain possible by spraying silver iodide on clouds ?
Answer:
Clouds are charged due to colloidal nature. Silver iodide is an electrolyte. Spray¬ing it on clouds lead to coagulation by which it rains.

Question 9.
How is the adsorption of a gas related to its critical temperature ?
Answer:
Higher is the critical temperature of a gas, greater is the ease of liquification of gas i.e., larger are the van der Waals’ forces of attraction. Therefore, greater is the adsorption.

Question 10.
What happen when a freshly precipitated Fe(OH)₃ is shaken with little amount of dilute solution of FeCl₃ ?
Answer:
A reddish brown colloidal solution of Fe(OH)₃ is obtained. This process is called peptization. The Fe⁺³ ions from FeCl₃ are absorbed on the surface of the precipitate and form positively charged colloidal solution.
Fe(OH)₃ + Fe⁺³ → [Fe(OH)₃]Fe⁺³

Surface Chemistry Short Answer Type Questions

Question 1.
What is meant by colloidal solution ? What is dialysis ? What is its principle ?
Answer:
Colloidal solution: The solutions in which solute particles are of 10^-7 cm. to 10^-4 cm. iameter and solvent particles are within 10^-8 cm. to 10^-7 cm., are called colloidal solution. Colloidal solutions are heterogeneous in nature.
Dialysis : The process by which dissolved impurities are removed with the help of parchment paper or membrane, is called dialysis.
Colloidal solution is filled in a bag, made of parchment paper and suspended in distilled water. Particles of dissolved crystalloids come out of the bag and are diffused in the water. Thus, the colloidal solution is purified.

Question 2.
Define Sol, Gel and Emulsion with example.
Answer:
When the dispersed phase of colloidal solution is solid and dispersion medium is liquid, it is called sol.
e.g., Colloidal solutions of ferric hydroxide, gold etc. in water.
Gel: When any liquid is dispersed in solid and form colloidal solution, is called gel.
e.g., Paneer, butter etc.
Emulsion : When dispersed state and dispersion medium both are liquid, it is called emulsion.
e.g., Milk, Cream etc.

Question 3.
What is homogeneous and heterogeneous catalysis ? Explain with example.
Answer:
Homogeneous catalysis : The chemical reaction in which reactants and catalysts are in same physical state, are example of homogeneous catalysis.
Example : In lead chamber process of manufacturing of sulphuric acid reactant and catalyst NO are in same physical state – gaseous.

Heterogeneous catalysis : The chemical reactions in which reactants and catalysts are in different physical state, are examples of heterogeneous catalysis.
Example: In Haber process manufacture of Ammonia.

Question 4.
What is ‘Gold number’ ? Explain with example.
Answer:
Gold Number: Protective actions of different lyophilic colloids are compared with gold number. Gold number can be defined as :

“Gold number is the number of miligrams of protective colloid (Lyophilic) which on adding prevents the coagulation of 10 ml. standard gold sol by addition of 1 ml. of 10% NaCl solution.”

Thus smaller the value of gold number, higher is it’s protecting action.

For example, gold number of gelatin and gum arobic are 0.005 and 015 respectively. It means gelatin is better protective colloid because it’s only 0-005 mg quantity is required to prevent coagulation if 10 ml Au sol by addition of 1 ml. 10% NaCl.

Question 5.
What is the importance of emulsifying agents in emulsifications ?
Answer:
The process of making emulsions is called emulsification. Emulsions are formed when suitable liquids are mixed and shaked, but the emulsions are thus formed are not stable. To make these emulsions stable some other substances are added, which are known as emulsifying agents. Soap, gum, starch etc. act as emulsifying agents. In absence of emulsifying agents, disperse drops of liquid meet each other to distroy emulsion state. It is supposed that emulsifying agents form membrane at interphase of oil and water which checks the union of droplets.

Question 6.
What is adsorption ? Give its two example and explain its mechanism.
Answer:
Adsorption is a surface phenomenon in which particles of different substances or gases are temporary linked with the surface of liquid or solids to satisfy the free valencies of solid surfaces.
Examples of adsorption :
(i) In sugar industry, animal charcoal adsorbs coloured materials.
(ii) In permutit process, Ca²⁺, Mg²⁺ ions are adsorbed and Na+ ion are released by which hardness of water is removed.

Mechanism of adsorption : Atoms or molecules present on the surface of solid con¬tain free valencies. These free valencies attract the molecules of adsorbate.

Question 7.
What do you understand by Electro-dialysis ?
Answer:
Electro-dialysis : Particles of true solutions pass through parchment paper or cellophane but sol particles cannot pass through such membranes. In dialysis, the sol filled in a bag of parchment or cellophane is suspended in pure water. This process is very slow and takes a long time for completion. However, it can be quickened under the influence of an electric field and the process is known as Electro-dialysis.

Artificial kidney used in medical science works on the principle of dialysis.

Question 8.
What do you understand by protective colloids ?
Answer:
Protective colloid: On adding small quantity of electrolyte, Lyophobic colloids easily coagulated but if some quantity of hydrophillic colloid is added in Lyophobic colloids, it minimize the effect of addition of electrolyte and coagulation is prevented or very slowly coagulated. This process is called protection of colloid. The hydrophillic colloid which is responsible for protection against coagulation is called protective colloid.

Example: If a small amount of gum, gelatin or starch is added to As₂S₃ sol, its coagulation of NaCl solution is prevented. Thus starch, gum or gelatin protects the As₂S₃ sol.

Question 9.
Give the method of preparation of colloidal solution of ferric hydroxide and sulphur in water.
Answer:
(i) To prepare sol of ferric hydroxide, FeCl₃ solution is added in the boiling water dropwise with shaking. Excess of FeCl₃ and HCl are separated by electrodialysis and sol is also stabilized by this.
FeCl₃ + 3H₂O → Fe(OH)₃ + 3HCl

(ii) H₂S gas is passed in the solution of nitric acid (oxidising agent) and colloidal solution of sulphur is obtained.
2HNO₃ + H₂S → S + 2H₂O + 2NO₂.

Question 10.
Explain physical and chemical adsorption.
Answer:
In physical adsorption the adsorbate molecules are all reacted by van der Waals’ forces on the surface of adsorbent. These van der Waals’ forces are weak in nature. The physical adsorption is also known as van der Waals’ adsorption or physical adsorption.
In chemical adsorption, the adsorbate molecules are attached with adsorbent through some chemical bonds, because some unsatisfied free valencies exist m the surface of adsorbent. This adsorption is also known as chemisorption.

Question 11.
What do you understand with enthalpy of adsorption ?
Answer:
In adsorption process, when one mole of adsorbate is adsorbed on the surface of adsorbent, the enthalpy change in this is called enthalpy of adsorption or heat of adsorption. The enthalpy of adsorption for chemisorption as about 400 kJ/mol while in physical adsorption it is about 40 kJ/mol.

Question 12.
What is catalysis ? Explain induced catalysis with an example.
Answer:
Catalysis : A catalyst is a substance which alters the rate of chemical reaction without being used in the reaction and the phenomenon is known as catalysis.
Induced Catalysis : In induced catalysis, one reaction already taking place, catalyse the other reaction also which does not occur separately.
Example : Sodium sulphite (Na₂SO₃) oxidise in the atmosphere easily while sodium arsenite (Na₃AsO₃) does not oxidise in atmosphere separately. When (Na₂SO₃) and Na₃AsO₃ both are kept together, both are oxidised.

Question 13.
Explain positive and negative catalysis with example.
Answer:
Positive Catalysis : When the velocity of any chemical reaction increases with the presence of catalyst, this type of catalysis is called positive catalysis.

Negative Catalysis : Catalysts when decrease the velocity of chemical reaction are called negative catalysts or retarders and the process is known as negative catalysis.

Question 14.
What is peptization ? Explain.
Answer:
Peptization : Peptization is a good method of preparing colloidal sols from precipitates. A fresh precipitate is taken for the purpose and a suitable reason or peptizing agents are added. These peptizing agents are generally dilute solutions of electrolytes of common ion. Peptization process is op-posite of the process of coagulation.

Example : When fresh precipitate of aluminium hydroxide is boiled with dilute HCl mixed water, colloidal solution of Al(OH)₃ is obtained.

When an electrolyte is added to a fresh precipitate then the particles of the electrolyte preferentially adsorbs an ion and due to electrostatic repulsion undergo in colloidal state. On adding electrolyte ferric chloride to ferric hydroxide precipitate, sol of ferric hydroxide is obtained.

Question 15.
Deduce the origin of electrical charge on colloidal particles.
Answer:
Colloidal particles have electrical charge and all colloidal particles of any colloidal solution have similar positive or negative charge. To explain origin of charge, following theories are given :
(i) Due to internal friction : According to this theory charge on colloidal particles originates due to mutual friction of dispersion medium and dispersed phase.
(ii) By ionisation of groups present in surface: Colloidal particles may also acquire charge by direct ionisation of different groups present in the surface. These groups may be either colloidal particles or any electrolyte added to prevent coagulation.
(iii) Electrical double layer theory : According to this theory electrical charge on colloidal particles is double layered. One layer is consist of absorbed ions and other layer is diffused layer which is consist of oppositely charged ions in dispersion medium.

Question 16.
Give reason :
(i) Milk turns sour on adding acid to it.
(ii) Alum is added to purify water.
(iii) Delta is formed where river water meets sea.
Answer:
(i) Milk is an emulsion of fats dispersed in water. Albumin and caesin are emulsifiers. Addition of acid destroys emulsifiers and hence milk gets coagulated.
(ii) In impure water, soil particles, bacteria and other soluble impurities are dissolved.
When alum is added, the Al⁺³ ion present in alum destroys the negative charge of impure water. Due to neutralization of charge the impurities are coagulated and settle down.
(iii) In the river water negatively charged particles of soil and sand are present. When river water meets sea-water, various salts present in sea water causes coagulation and soil particles etc. are settle down. Thus a delta is formed.

Question 17.
Write characteristics of catalysts.
Answer:
Characteristics of catalysts :

1. No participation : Catalysts do not participate in the chemical reaction. Only it’s physical state may be changed.
2. Small quantity : A small quantity of catalyst is always required for catalysing reaction.
3. No effect in equilibrium: Catalysts do not affect equilibrium state because catalyse both forward and backward reactions.
4. Specific nature: Catalysts are of specific nature and catalyse only definite reaction not all.
5. Effective temperature : There is a optimum temperature in which catalyst’s activity is maximum
6. Promotors and Catalytic poisons : There are some substances which increase the activity of catalyst, by their presence. These substances are known as promotors. Catalytic poisons are substances which destroy the catalytic activity.

Question 18.
Coloured glass, smoke, milk, cream, fog, jelly, pumic stone and soap lather belongs to which type of colloidal system? Name them.
Answer:

Question 19.
Compare the properties of true solution, colloidal solution and suspension.
Answer:
Distinction between True solution, Colloidal solution and Suspension :

Question 20.
What do you understand by activation of the adsorbent ? How is it obtained ?
Answer:
Activation of adsorbent means, increasing the activation power of adsorbent. It can be done by increasing the surface area of adsorbent which can be obtained as follows :

1. By removing the adsorbed gases or by heating charcoal in vacuum to extremely high temperature in steam at 650K to 1330K temperature.
2. By breaking the adsorbate into small pieces.
3. By making the surface of adsorbent rough.

Question 21.
What is the role of adsorbent in heterogenous catalysis ?
Answer:
Generally in heterogenous catalysis, adsorbate is in gaseous where as catalyst is in solid state. Adsorbate molecules are adsorbed on the surface of solid catalyst by physical or chemical adsorption. Due to increase in concentration of adsorbed molecules or by the formation of active species due to breaking up of adsorbed molecules due to reaction occurs fast. Product molecules are desorbed and catalytic surface again becomes available for the adsorption of reactant molecules. This principle is known as adsorption of heterogenous catalysis.

Surface Chemistry Long Answer Type Questions

Question 1.
Explain the following :
(i) Brownian movement
(ii) Autoca-talysis.
Answer:
(i) Brownian movement : It is observed by an ultra-microscope that colloidal particles move in a zig-zag path in all possible directions. Thus, zig-zag or random motion of sol particles is called Brownian movement. It is caused due to unequal bombardment of Small particle the molecules of dispersion medium on the sol particles. First of all this type of movement is reported by Robert Brown so it is known as Brownian movement. On increasing the size of particles, their movements also decreases and in suspension it is finished.

(ii) Autocatalysis: In autocatalysis, one of the product behave as catalyst and increases the velocity of reaction.
Example : Hydrolysis of Ethyl acetate forms Acetic acid which act as autocatalyst.
CH₃COOC₂H₅ + H₂O → [CH₃COOH] + C₂H₅OH
Acetic acid

Question 2.
Write differences between lyophilic and lyophobic colloids.
Answer:
Differences between Lyophilic and Lyophobic colloids :

 

Property	Lyophilic colloid	Lyophobic colloid
1. Stabilization	Self stabilized. Do not need any electrolyte for stabilization.	Low stability, carry small quantities of electrolytes added for stabilization.
2. Method of preparation	Easily prepared by dissolving in the solvent.	Colloidal solution is prepared by special methods.
3. Nature	Reversible. It can be re con­verted to the sol state by simply agitating them with the dis­persion medium.	Irreversible. Once coagulated cannot be reconverted.
4. Hydration	Particles are heavily hydrated.	Particles are usually poorly hydrated.
5. Viscosity and surface tension	Surface tension generally lower and viscosity much higher than that of water.	Surface tension and viscosity almost equal to that of water.

Question 3.
Write Hardy Schulze’s law.
Answer:
Hardy-Schulze’s law : Coagulating power of an ion is governed by this law according to which, “Greater the valency of an ion greater will be its coagulating power.”

Thus, to coagulate negative sol, the coagulating power of different cations are found to be in the order :
\(\mathrm{Sn}^{4+}>\mathrm{Al}^{3+}>\mathrm{Ba}^{2+}>\mathrm{Na}^{+}\)
Similarly for the coagulation of a positive sol of Fe(OH)3, the coagulating power of different anions is found to be in the order :
\(\mathrm{PO}_{4}^{3-}>\mathrm{SO}_{4}^{2-}>\mathrm{Cl}^{-}\)

Question 4.
Explain intermediate compound theory of catalysis.
Answer:
Intermediate compound theory of catalysis : Various theories are given to explain the mechanism of catalysis. This theory explains the mechanism of liquid and gaseous catalysts. According to this theory catalyst combines with one of the reactant and form an intermediate compound. This intermediate compound then reacts with other reactant and form aspected compound and catalyst is released which again acts as catalyst.

For example, if A and B combine and form a compound AB where X is catalyst then AX is intermediate compound.
A + X → AX (intermediatecompound)
AX + B → AB + X
The time in this reaction is less than time required when A and B combine directly.

Example: In lead chamber process of manufacturing of H₂SO₄, NO acts as catalyst. NO combines with oxygen to form NO₂ as intermediate compound. NO₂ now reacts with other reagent SO₂ and form SO₃, the catalyst NO released which further enhance the chain.

Question 5.
Write any five differences between enzyme catalyst and normal catalyst.
Answer:
Differences between enzyme catalyst and normal catalyst:

Enzyme catalyst:

1. Is the catalyst for biochemical reactions.
2. These are active at normal body temperature and pH.
3. These are produced in living cells and are protein in normal form.
4. Their molecular mass are high.
5. These become inactive at low temperature.

Normal catalyst

1. Is the catalyst for normal chemical reactions.
2. These function at a definite favourable temperature.
3. These can be metals, non-metals or compounds of non-metals.
4. Their molecular mass are low. These are also ineffective at low temperature.

Question 6.
What is adsorption ? Explain the factors affecting it
(a) On what factors does the extent of adsorption of gases on solid depend ?
(b) Write five applications of adsorption.
Answer:
Adsorption: Refer Short Answer Type Q. No. 6.
(a) The extent of adsorption of a gas on a solid adsorbent is affected by the following factors:

1. Nature of the gas: Under given conditions of temperature and pressure, the easily liquefiable gases like NH3, C02, HC1, etc. are adsorbed to a greater extent than permanent gas.
2. Nature of the adsorbent: Activated charcoal is the most common adsorbent for the gases which are easily liquefied.
3. Specific area of the solid : Greater the specific area of the solid, greater will be its adsorption power.
4. Pressure of the gas : The extent of adsorption increases with increase in pres¬sure.
5. Effect of temperature: Adsorption at a surface initially increases till a saturation point is achieved and to this point equilibrium is developed. The magnitude of adsorption decreases with rise in temperature.
6. Activation of adsorbent: The adsorption power can be increase by making the surface of adsorbent rough or by breaking it into small pieces. Adsorption power decreases if the particles are made very small because the interparticle space will be two small to allow penetration.

(b) Various applications of adsorption are in our daily life. Some important applications are:

1. In Catalysis : In industries various catalysts are used to promote the reaction. These catalysts are generally based on adsorption principle. e.g., Haber process of ammonia, preparation of sulphuric acid by contact process etc.
2. In gas masks : Activated charcoal is used to adsorb harmful gases as CO,CH₄ etc. Activated charcoal or any other suitable adsorbent are kept in gas masks.
3. In creating vacuum : High vacuum can be created by adsorbing gases by adsorbents.
4. For decolourising and de-odourising sugar : Animal charcoal is used for decolourising sugar and in de-odourising process.
5. In chromatography: Purification of compounds by chromatography is also based on adsorption theory.

Question 7.
Write five applications of colloidal chemistry.
Answer:
The five applications of colloidal chemistry are as follows :
1. In medicines : Colloidal medicines are easily adsorbed by body tissue and are more effective, e.g., Argyrol, colloidal antimony, colloidal gold etc.

2. Smoke precipitation : Smoke and dust are also colloidal in nature and smoke precipitation is based on the principle of electrophoresis. Cottrell precipitator is nowadays commonly used in various industries.

3. Colloids in nature : Different forms of colloidal solutions can be seen in nature. Delta formation, fertile soil, rain, blue colour of sky are some examples of colloidal solutions.

4. Action of Soap: Cleaning action of soap is explained on the basis that soap solution is colloidal. Soap emulsifies greasy and oily materials sticking on the surface of body or clothes.

5. In leather industry: The colloidal particles in hides are positively charged and on soaking the hide in tannin solution (a negative solution) mutual coagulation takes place. This process is called tanning and it makes the hide hard. Solutions of chromium salts are used in place of tannin with advantage and the process is called chrome-tanning.

MP Board Class 12th Chemistry Solutions

MP Board Class 12th Biology Solutions Chapter 16 Environmental Issues

Environmental Issues NCERT Textbook Question and Answers

Question 1.
What are the various constituents of domestic sewage? Discuss the effects of sewage discharge on a river.
Answer:
Domestic sewage are the waste originating from the kitchen, toilet, laundry and other sources. They contain impurities such as suspended solid (sand, salt, clay), colloidal materials (faecal matters, bacteria, plastic and cloth fiber), dissolved materials (nitrate, phosphate, calcium, sodium, ammonia) and disease-causing microbes.

When organic wastes from the sewage enter the water bodies, they serve as a food source for microorganisms such as algae and bacteria. As a result, the population of these microorganisms in the water body increases. Here, they utilize most of the dissolved oxygen for their metabolism. This results in an increase in the levels of BOD in river water and results in the death of aquatic organisms. Also, the nutrients in the water lead to the growth of planktonic algal, causing algal bloom. This causes deterioration of water quality and fish mortality.

Question 2.
List all the wastes that you generate at home, school or during your trips to other places, could you very easily reduce. Which would be difficult or rather impossible to reduce?
Answer:
Wastes generated at home include plastic bags, paper napkin, toiletries, kitchen wastes (such as peelings of vegetables and fruits, tea leaves), domestic sewage, glass, etc.

Wastes generated at school include waste paper, plastics, vegetable and fruit peels, food wrapping, sewage, etc. Wastes generated at trips or picnics include plastic, paper, vegetable and fruit peels, disposable cups, plates, spoons etc.

Yes, wastes can be easily reduced by the judicious use of the above materials. Wastage of paper can be minimized by writing on both sides of the paper and by using recycled paper.

Plastic and glass waste can also be reduced by recycling and re-using. Also, substituting plastics bags with biodegradable jute bags can reduce wastes generated at home, school or during trips. Domestic sewage can be reduced by optimizing the use of water while bathing, cooking, and other household activities.

Non-biodegradable wastes such as plastic, metal, broken glass, etc. are difficult to decompose because microorganisms do not have the ability to decompose them.

Question 3.
Discuss the causes and effects of global warming. What measures need to be taken to control global warming?
Answer:
Global warming is defined as an increase in the average temperature of the Earth’s surface due to greenhouse effect.

Causes of global warming: Global warming occurs as a result of the increased concentration of greenhouse gases in the atmosphere. Greenhouse gases include carbon dioxide, methane and water vapour. These gases trap solar radiation released back by the earth. Global warming is a result of industrialization, burning of fossil fuels, and deforestation.

Effects of global warming: Global warming is defined as an increase in the average temperature of the Earth’s surface. It has been observed that in the past three decades, the average temperature of the Earth has increased by 0-6°C. As a result, the natural water cycle has been disturbed resulting in changes in the pattern of rainfall. It also changes the amount of rainwater. Also, it results in the melting of polar ice caps and mountain glaciers, which has caused a rise in the sea level, leading to the inundation of coastal regions.

Control measures for preventing global warming:

• Reducing the use of fossil fuels
• Use of bio-fuels
• Improving energy efficiency
• Use of renewable source of energy such as CNG, etc.
• Reforestation.
• Recycling of materials.

Question 4.
Match the items given in column A and B :

Answer:

1. (b)
2. (a)
3. (c)
4. (d)

Question 5.
Write critical notes on the following :
(a) Eutrophication.
(b) Biological magnification.
(c) Groundwater depletion and ways for its replenishment
Answer:
(a) Eutrophication : It is the natural ageing process of lake caused due to nutrient enrichment. It is brought down by the runoff of nutrients such as animal wastes, fertilizers, and sewage from land which leads to an increased fertility of the lake. As a result it causes a tremendous increase in the primary productivity of the ecosystem. This leads to an increased growth of algae, resulting into algal blooms. Later, the decomposition of theses algae depletes the supply of oxygen, leading to the death of other aquatic animal life.

(b) Biological magnification : The increase in concentration of harmful non- biodegradable substances into higher tropic level is called biological magnification. DDT used to protect the crops reach the soil and are absorbed by plants with water and minerals from the soil. Due to rain, these chemicals can also enter water sources and into the body of aquatic plants and animals. As a result, chemicals enter the food chain. Since, these chemicals cannot be decomposed, they keep on accumulating at each trophic level. The maximum concentration is accumulated at the top carnivore’s level.

The producers (phytoplankton) were found to have 0 04 ppm concentration of DDT. Since many, types of phytoplankton were eaten by zooplankton (consumers), the concentration of DDT in the bodies of zooplankton as found to be 0-23ppm. Small fish that feed on zooplankton accumulate more DDT in their body. Thus, large fish (top carnivore) that feed on several small fish have the highest concentration of DDT.

(c) Groundwater depletion and ways for its replenishment : The level of ground¬water has decreased in the recent years. The source of water supply is rapidly diminishing each year because of an increase in the population and water pollution. To meet the demand of water, water is withdrawn from water bodies such as ponds, rivers, etc.

As a result, the source of groundwater is depleting. This is because the amount or groundwater being drawn for human use is more than the amount replaced by rainfall. Lack of vegetation cover also results in very small amounts of water seeping through the ground. An increase in water pollution is another factor that has reduced the availability of groundwater.

Measures for replenishing groundwater:

• Preventing over-exploitation of groundwater.
• Optimizing water use and reducing water demand.
• Rainwater harvesting.
• Preventing deforestation and plantation of more trees.

Question 6.
Why ozone hole forms over Antarctica? How will enhanced ultraviolet radiations affect us?
Answer:
The ozone hole is more prominent over the region of Antarctica. It is formed due to an increased concentration of chlorine in the atmosphere. Chlorine is mainly released ‘from Chlorofluorocarbons (CFC’s) widely used as refrigerants. The CFC’s release chlorine atoms by the action of UV rays on them. The release of chlorine atoms causes the conversion of ozone into molecular oxygen. One atom of chlorine can destroy around 10,000 molecules of ozone and causes ozone depletion.
CF₂Cl₂ → CF₂Cl+ Cl
Cl + O₃ → ClO+O₂
ClO + O₂ → Cl+O₂
The formation of the ozone hole will result in an increased concentration of UV-B radiation on the Earth’s surface. UV-B damages DNA and activates the process of skin ageing. It also causes skin darkening and skin cancer. High levels of UV-B cause corneal cataract in human beings.

Question 7.
Discuss the role of women and communities in protection and conservation of forests.
Answer:
Women and communities have played a major role in environmental conservation movements.

The Bishnoi community in Rajasthan strictly believes in the concept of living peacefully with nature. In 1731, the King of Jodhpur ordered his ministers to arrange wood for the construction of his new palace. For this purpose, the minister and the workers went to bishnoi village. There, a Bishnoi woman called Amrita Devi along with her daughter and hundreds of other Bishnoi’s showed the courage to step forward and stop them from cutting trees. They embraced the trees and lost their lives at the hands of soldiers of the king. This resistance by the people of the village forced the king to give up the idea of cutting trees.

The Chipko movement was started in 1974, in die Garhwal region of the Himalayas. In this movement, the women from the village stopped the contractors from cutting forest trees by embracing them.

Question 8.
What measures, as an individual you would take to reduce environmental pollution?
Answer:
The following initiatives can be taken to prevent environmental pollution:

Measures for preventing air pollution:

• Planting more trees.
• Use of clean and renewable energy sources such as CNG and Bio-fuels.
• Reducing the use of fossil fuels.
• Use of catalytic converters in automobiles.

Measures for preventing water pollution :

• Optimizing the use of water.
• Using kitchen waste water in gardening and other household purposes measures for controlling noise pollution:
  • Avoid burning crackers on Diwali,
  • Plantation of more trees. ‘

Measures for decreasing solid waste generation:

• Segregation of waste.
• Recycling and reuse of plastic and paper.
• Composting of biodegrable kitchen waste.
• Reducing the use of plastics.

Question 9.
Discuss briefly the following:
(a) Radioactive wastes. ‘
(b) Defunct ships and e-wastes.
(c) Municipal solid wastes.
Answer:
(a) Radioactive wastes : Radioactive wastes are generated during the process of generating nuclear energy from radioactive materials. Nuclear waste is rich in radioactive materials that generate large quantities of ionizing radiation such as gamma rays. These rays cause mutation in organisms which often results in skin cancer. At high dosage, these rays can be lethal. Safe disposal of radioactive wastes is a big challenge. It is recommended that nuclear wastes should be stored after pre-treatment in suitable shielded containers, which should then be buried in rocks.

(b) Defunct ships and e-wastes : Defunct ships are dead ships that are no longer in use. Such ships are broken down for scrap metal in countries such as India and Pakistan. These ships are a source of various toxicants such as asbestos, lead, mercury etc. Thu$,4hey contribute to solid wastes that are hazardous to health. E-wastes or electronic wastes generally include electronic goods such as computers, etc.

Such wastes are rich in metals such as copper, iron, silicon, gold, etc. These metals are highly toxic and pose serious health hazards. People of developing countries are involved in the recycling process of these metals and therefore, get exposed to toxic substances present in these wastes.

(c) Municipal solid wastes : Municipal solid wastes are generated from schools, offices, homes and stores. It is generally rich in glass, metal, paper waste, food, rubber, leather and textiles. The open dumps of municipal wastes serve as a breeding ground for flies, mosquitoes and other disease-causing microbes. Hence, it is necessary to dispose municipal solid waste properly to prevent the spreading of diseases. Sanitary landfills and incineration are the methods for the safe disposal of solid wastes.

Question 10.
What initiatives were taken for reducing vehicular air pollution in Delhi? Has air quality improved in Delhi?
Answer:
Delhi has been categorized as the fourth most polluted city of the world in a list of 41 cities. Burning of fossil fuels has added to the pollution of air in Delhi. Various steps have been taken to improve the quality of air in Delhi:

• Introduction of CNG (Compressed Natural Gas): By the order of the supreme court of India, CNG-powered vehicles were introduced at the end of year 2006 to reduce the levels of pollution in Delhi. CNG is a clean fuel that produces very little unbumt particles.
• Phasing out of old vehicles.
• Use of unleaded petrol.
• Use of low-sulphur petrol and diesel.
• Use of catalytic converters.
• Application of stringent pollution-level norms for vehicles.
• Implementation of Bharat stage I, which is equivalent to euro II norms in vehicles of major Indian cities.
• The introduction of CNG-powered vehicles has improved Delhi’s air quality, which has lead to a substantial fall in the level of CO₂ and SO₂. However, the problem of Suspended Particulate Matter (SPM) and Respiratory
• Suspended Particulate Matter (RSPM) still persists.

Question 11.
Discuss briefly the following:
(a) Green house gases
(b) Catalytic converter
(c) Ultraviolet-B.
Answer:
(a) Green house gases: The greenhouse effect refers to an overall increases in the average temperature of the earth due to the presence of greenhouse gases. Greenhouse gases mainly consist of carbon dioxide, methane and water vapour. When solar radiation reach the Earth, some of these radiation are absorbed. These absorbed radiation are released back into the atmosphere. These radiation are trapped by the greenhouse gases present in the atmosphere. This helps in keeping our planet warm and thus, helps in human survival. However an increase in the amount of greenhouse gases can lead to an excessive increase in the Earth’s temperature, thereby causing global warming.

(b) Catalytic converter: Catalytic converters are devices fitted in automobiles to reduce vehicular pollution. These devices contain expensive metals such as platinum, palladium and rhodium that act as catalysts. As the vehicular discharge passes through the catalytic converter, the unburnt hydrocarbons present in it get converted into carbon dioxide and water. Carbon monoxide and nitric oxide released by catalytic converters are converted into carbon dioxide and nitrogen gas (respectively).

(c) Ultraviolet-B: Ultraviolet-B is an electromagnetic radiation which has a shorter wavelength than visible light. It is a harmful radiation that comes from sunlight and penetrates through the ozone hole on to the earth’s surface. It induces many health hazards in humans. UV-B damages DNA and activates the process of skin ageing. It also causes skin darkening and skin cancer. High levels of UV-B cause corneal cataract in human beings.

Environmental Issues Other Important Question and Answers

Environmental Issues Objective Type Questions

1. Choose the Correct Answer:

Question 1.
It is a greenhouse gas:
(a) H₂
(b) CO
(c) CO₂
(d) N₂
Answer:
(c) CO₂

Question 2.
Combustion of fissil fuel resulting in:
(a) SO₂ pollution
(b) NO₂ pollution
(c) N₂O pollution
(d) NO pollution.
Answer:
(a) SO₂ pollution

Question 3.
The causes of greenhouse effect is the increase in the concentration of:
(a) CO₂
(b) CO
(c) O₃
(d) Nitrogen oxide.
Answer:
(a) CO₂

Question 4.
Which of the following is responsible for the reduction of 03 from the atmosphere :
(a) CFC
(b) NO₂
(c) CO₂
(d) SO₂
Answer:
(a) CFC

Question 5.
Which of the following is highly dangerous radioactive pollutant:
(a) Strontium-90
(b) Phosphorus-32
(c) Sulphur-35
(d) Calcium-40.
Answer:
(a) Strontium-90

6. Causes of acid rain is:
(a) SO₂ pollutant
(b) CO
(c) Insecticide pollution
(d) Dust pollution.
Answer:
(a) SO₂ pollutant

Question 7.
Carbon monoxide is the chief pollutant of:
(a) Water
(b) Air
(c) Noise
(d) Soil.
Answer:
(b) Air

Question 8.
Plants are the purifier of air because:
(a) Respiration
(b) Photosynthesis
(c) Transpiration
(d) Drying.
Answer:
(a) Respiration

Question 9.
Bhopal gas tragedy of 1984 took place because methyl isocyanate related with:
(a) DDT
(b) Ammonia
(c) CO₂
(d) Water.
Answer:
(d) Water.

Question 10.
Maximum ozone layer depletion is caused by :
(a) CO₂
(b) CFC
(c) SO₂
(d) CH4.
Answer:
(b) CFC

Question 11.
Minimata disease is caused by the pollution of:
(a) Mercury and Lead
(b) Mercury and Cadmium
(c) Lead and Tin
(d) Lead and Strontium.
Answer:
(b) Mercury and Cadmium

Question 12.
Taj Mahal is affected by :
(a) Air pollution due to Mathura refinery
(b) Decomposition of marble
(c) Pollution of Yamuna
(d) All of the above.
Answer:
(a) Air pollution due to Mathura refinery

Question 13.
Which of the following is not a pollutant:
(a) Thermal energy plant
(b) Automatic vehicles
(c) Nuclear power energy plant
(d) Hydroelectric project.
Answer:
(d) Hydroelectric project.

Question 14.
Green house effect is increase in temperature of earth due to :
(a) High concentration of NO₂
(b) High concentration of SO₂
(c) High concentration of CO₂
(d) High concentration of CO.
Answer:
(c) High concentration of CO₂

Question 15.
Green house gases are:
(a) CO₂, CFC, CH_4, NO₂
(b) CO₂, O₂, N₂, NO₂, NH₃
(c) CH₄, N2, CO₂, NH₃
(d) CFC, CO_2, NH₃, H₂
Answer:
(d) CFC, CO₂, NH₃, H₂.

Question 16.
Which of the following is an indicator of water pollutant:
(a) BOD
(b) COD
(c) E. coli
(d) All of the above
Answer:
(a) BOD

Question 17.
Cause of water pollution is :
(a) 2,4-D and insecticides
(b) Smoke
(c) Automatic engines
(d) Aeroplanes.
Answer:
(a) 2,4-D and insecticides

Question 18.
Polluted water is treated by :
(a) Lichen
(b) Fungi
(c) Fern
(d) Phytoplankton
Answer:
(d) Phytoplankton

Question 19.
Which country produce maximum green house gas:
(a) India
(b) Brazil
(c) USA
(d) France.
Answer:
(c) USA

Question 20.
Which are not affected by acid rain :
(a) Lithosphere
(b) Plants
(c) Ozone layer
(d) Animals.
Answer:
(c) Ozone layer

Question 21.
Ozone hole causes:
(a) Global warming
(b) Reduction in the rate of photosynthesis
(c) More UV rays come to earth
(d) All of the above.
Answer:
(c) More UV rays come to earth

Question 22.
Highly polluted river of India is :
(a) Ganga
(b) Yamuna
(c) Gomti
(d) Hugh.
Answer:
(a) Ganga

Question 23.
Effect of pollution is forst marked on:
(a) Microorganism
(b) Vegetation
(c) Food crops
(d) None of the above
Answer:
(b) Vegetation

Question 24.
Ozone hole enhances:
(a) UV-radiations reaching earth
(b) Number of characters
(c) Skin cancer
(d) All of the above.
Answer:
(d) All of the above.

2. Fill in the Blanks :

1. …………………… is everything that is around us.
2. …………………. Nature of environmental study is
3. …………………. is the highest layer of the earth.
4. An interacting group of various species in a common location is called……………………..
5. …………………….. is a layer or a set of layers of gases surrounding a planet.
6. ……………………….. is electromagnetic radiation within a certain portion of the electromagnetic spectrum.
7. The is defined as a vertical section of the soil. ……………………….
8. …………………… water is available in plants easily.
9. ……………………. is essential for respiration of animals which are found in the soil.
10. …………………… is essential part of the earth for continuity of life.
11. …………………… gas is essential for life.
12. …………………….. fish is used to eat the larva of mosquitoes.
13. Quantity of atmospheric C02 is …………………… by forestation.
14. Soil pollution is caused by ……………………..
15. ………………….. rays are absorbed by ozone layer.

Answers:

1. Environment
2. Multidisciplinary
3. Biosphere
4. Bio-community
5. Atmosphere
6. Light
7. Soil profile
8. Capillary
9. Oxygen
10. Death
11. Oxygen
12. Gambusia
13. Balanced
14. Chemical fertilizers
15. Ultraviolet rays.

3. Match the Following :
(i)

Answer:

1. (c)
2. (a)
3. (d)
4. (b).

Answer:

1. (c)
2. (a)
3. (b)
4. (d).

Environmental Issues Very Short Answer Type Questions

Question 1.
The surroundings in which a person, animal or plant lives are called.
Answer:
Environment.

Question 2.
When two individuals can produce fertile offsprings, typically by sexual reproduction is called.
Answer:
Species.

Question 3.
What called, a biological community of interacting organisms and their physical environment?
Answer:
Ecosystem.

Question 4.
Name the lower part of the atmosphere which has found more than 90% gases.
Answer:
Troposphere,

Question 5.
Rays of light which are low wavelength from purple colour rays?
Answer:
Ultraviolet rays.

Question 6.
Light effect of flowering in plants.
Answer:
Photoperiodism.

Question 7.
Smallest particle which are found in soil.
Answer:
Clay.

Question 8.
Water which are absorbed from the atmosphere and held very tightly by the soil particles.
Answer:
Hygroscopic water.

Question 9.
Plants are one marked by short life-cycle.
Answer:
Ephemeral plant.

Question 10.
When an animal or plant resembles another creature or in animate object?
Answer:
Mimicry.

Question 11.
Expand BOD.
Answer:
Biological Oxygen Demand.

Question 12.
Name two gases which are caused air pollution.
Answer:
SO₂ and CO₂.

Question 13.
How much is hearing capacity of man?
Answer:
10 to 12 decibels.

Question 14.
Write the name of highly polluted river of India.
Ans.
Ganga.

Question 15.
What is called the increase in atmospheric temperature due to increased C02 concentration?
Answer:
Greenhouse effect.

Question 16.
Write the full form of DDT.
Answer:
Dichloro Diphenyl Trichloroethane.

Question 17.
How much quantity of CO₂ in atmosphere.
Answer:
0 03%.

Question 18.
Smoke which is caused eye irritation.
Answer:
No.

Question 19.
When the World Environment Day is celebrated?
Answer:
5th June.

Question 20.
Write the full form of PAN.
Answer:
Peroxy Acetyle Nitrate.

Question 21.
Write the full form of CFCs.
Answer:
Chlorofluourocarbons.

Question 22.
How much percent found of CO₂ in atmospheric temperature?
Answer:
60 %.

Environmental Issues Short Answer Type Questions

Question 1.
What is the definition of pollution?
Answer:
Pollution is defined as an undesirable change in physical, chemical or biological characteristics of air, land, water and soil.

Question 2.
What are the cause of air pollution?
Answer:
The causes of air pollution: The main causes of air pollutions are fossil fuels industries, factories and particulate matter are produced due to combustion of petrol, diesel, kerosene etc. in vehicles, houses and factories which pollute air.

In thermal power plants, steel and glass industries, paper and sugar mills etc. combustion of coal and furnace oil produce carbon monoxide, carbon dioxide, sulphur dioxide, ash, dust particles and some heavy metals which are released into atmosphere. Similarly various types of chemicals released from cloth mills, cement industries, asbesters industries, pesticides, industries etc. also causes air pollution.

Question 3.
What is acid rain? Write any two effects of acid rain on human beings.
Ans.
Acid rain: SO₂ gas is released into the environment by burning of fossil fuels containing sulphide from industries. e.g., Coal. In presence of moisture SO₂ reacts with water and forms the droplets of sulphurous and sulphuric acid in the environment. Likewise nitrogen oxides released from motor vehicles, burning materials and chemical industries . also react with water to produce the droplets of nitric acid. The droplets of sulphurous, sulphuric acid and nitric acids fall down on the earth with rainwater and thus, it is known as acid rain.
SO₂ + \(\frac { 1 }{ 2 }\)O₂ → SO₃
H₂O +SO₃ →H₂SO₄
H₂O + NO₂ → HNO₃
Effects on human beings: Skin diseases, irritation, metabolic diseases.

Question 4.
Write short note on pollution caused due to combustion activities.
Answer:
Combustion of fuel, such as wood, coal, natural gas for cooking and for some other purposes gives out gases like CO₂, CO, SO₂ and consumes oxygen from the air.

Question 5.
Write the effect of air pollution in plants.
Answer:
Effect of air pollution on plants :

• Increase in the concentration of SO₂ causes chlorosis of leaves in plants.
• The cells and chlorophyll of leaves are degraded and fall down.
• Vegetative and reproductive growth is inhibited.
• The development of plant is inhibited.

Question 6.
Write preventive measures to control air pollution.
Answer:
Measures for the control of air pollution :

• Industrial smokes must be filtered before releasing it into the atmosphere.
• Tree plantation should be increased and deforestation prevented.
• Use of automobiles should be minimized which reduce the nitrogen contents in the atmosphere.
• The use of crude fuels should be avoided and use of high quality fuels should be recommended.
• Nuclear explosions should be avoided.
• Legal control of air pollution.
• Plantation of air purifying plants.
• Development of parks and gardens in cities.

Question 7.
What is global warming? List four strategies for reducing global warming.
Answer:
Increase in the level of green house gases in the atmosphere causes the rise in global mean temperature called global warming. Four strategies for reducing global warming are:

1. Reducing deforestation.
2. Planting trees.
3. Slowing down the growth of human population.
4. Reduction in the emission of greenhouse gases.

Question 8.
Write any four measures to control green house effect
Answer:
Following important measures can be sited as the base steps towards controlling greenhouse effect:

• The aim is achieved to some extent by reducing the consumption of fossil fuels such as coal and petroleum. This can be achieved by depending more on non-conventional renewable sources of energy such as solar, wind, tidal, biogas and nuclear energies.
• Disposing of the greenhouse gases as they are formed elsewhere than in the atmosphere.
• By recovering greenhouse gases present already in the atmosphere and disposing them off elsewhere.
• Preventation of deforestation and planting of more trees.

Question 9.
Write short note :

1. Bio-magnification.
2. UV rays.
3. Bio digradable pollutants.
4. Non-biodegradable.

Answer:
1. Bio-magnification : Bio-magnification, also known as bio-amplification or biological magnification is the increasing concentration of a substance, such as a toxic chemical, in the tissues of organisms at successively higher levels in a food chain.

2. UV rays : Sunlight is the chief source of ultraviolet rays. The rays of sunlight having a wavelength range from 200 to 390 nm are called as UV rays.

Effect of UV rays: They have a direct effect on living cells. DNA and other chemical substances in cells are inactivated due to UV rays. Prevention of replication of the DNA molecule and its distortion cause many ill effects.

3. Non-biodegradable: The pollutants which cannot be purified by natural methods are called non-biodegradable pollutants. Plastic products, many chemicals, DDT, long chain detergents, glass aluminium, mercury salt and other synthetic products manufactured by man come under this category. These non-biodegradable pollutants not only accumulate but often “biologically magnified” as they move in biochemical cycles and along food chains.

4. Biodegradable: The pollutants which are degraded by natural factors and decomposed by natural activities are known as biodegradable pollutants, e.g., Domestic sewage, heat. The domestic sewage can be rapidly decomposed by natural processes or in engineered system (sewage treatment plant) that enhance natures great capacity to decompose and recycle.

Question 10.
What is the effect of SOz in the Environment?
Answer:

Question 11.
Write only the sources of water and air pollution.
Answer:
1. Sources of Water pollution: Following are the chief sources of water pollution:
(a) Human sources :

• Domestic sewage,
• Industrial effluents,
• Agricultural wastes,
• Oil pollution,
• Thermal and nuclear power station.

(b) Natural sources: Water pollution takes place by natural ways like soil erosion, mixing of metallic substances, plant leaves, humus and faecal matter of animals etc.

2. Sources of Air pollution: Following are the chief sources of air pollution:
(a) Human sources:

• Combustion activities,
• Industrial activities,
• Agricultural works,
• Use of solvents,
• Activities concerned with atomic energy.

(b) Natural sources: Volcano and its lava, ash, dust, smoke of forest fire, winds, cyclone. Decomposition of matters in the swamp water and liberation of methane gas and different compounds of hydrogen from forests plants, various pollen grains etc.

Question 12.
Write a note on the effect of water pollution on aquatic organisms.
Answer:
Effect of water pollution on aquatic plants:

• Inorganic nitrates and phosphates in excess amount stimulates excessive plant growth in lakes and reservoirs. These plants deplete the oxygen contents of the water during night. This leads to suffocation of fish and other aquatic life.
• The rapid algal growth leads to the diminishing of nutrient in the medium causing rapid decay of algal filament. This increases productivity of lake and stream water brought about by nutrient enrichment is called eutrophication.
• The number of microorganisms increases in polluted water.
• Siltation occurs in water.
• Temperature of water increases and 02 ratio is reduced.

Effect of water pollution on aquatic animals: Animal life depends on aquatic plants. Aquatic animals are affected from water pollution as follows :

• Decrease in the value of B.O.D. resulting in the number of aquantic animals.
• Animals found in freshwater and killed.
• Animal diversity is also decreased and fishes suffer from various types of diseases.
• Terrestrial animals are also affected by the use of polluted water.

Question 13.
Write the measures for control and prevention of water pollution.
Answer:
Measures for control and prevention of water pollution are:
Preventive measures:

• Use of harmful pesticides and weedicides must be stopped completely.
• Discharge of effluents into rivers, lakes and sea should be strictly prohibited without treatment.
• Oil spill should be prevented.
• Proper disposal of sewage so, that it does not find its way into water bodies.
• Preventing bathing, washing cloths, throwing dead bodies and other wastes into water source.

Curative measures:
1. Adequate waste water treatment: The domestic sewage and the industrial waste should be properly treated before its disposal into water ways.
Waste water treatment involves three steps :

(a) Primary treatment: During this treatment large objects and suspended undissolved solids are removed and converted into the sludge, a valuable fertilizer.

(b) Secondary treatment: Aeration is supplied to promote bacterial decomposition, followed by chlorination to reduce its content of bacteria.

(c) Tertiary treatment: During this phase nitrates and phosphates are removed. The treated water is then released. Sewage treatment is quite expensive and in many developing countries only the first two steps are followed.

2. Treatment of industrial effluents: Industrial effluents should be properly treated to remove the pollutants. These involve neutralization of acids and alkalies, removal of harmful chemicals, coagulation of colloidal impurities, precipitation of metallic compounds and reducing the temperature of wastes to decrease thermal pollution. Chemical oxidation can be achieved by chlorination through reaction with ozone. However, there are certain chemicals which are difficult to remove.

3. Recycling: One of the best methods of prevention and control of water pollution is the recycling of the various kinds of pollutants and wastes, e.g., Dung of cow and buffalo can be used for the production of gobar gas a cheap source of fuel and also as manure.

Question 14.
Write short notes on air pollution caused due to industries.
Answer:
Industrial pollution is caused by industrial pollutants which are released by the industries such as SO_2, CO₂ , CO, H₂S and hydrocarbons together with dust and smoke. These are produced by the burning of coal and petroleum.

The chemical industries releases HCl, Cl₂, nitrogen oxide, oxides of copper, zinc, lead, arsenic etc. Industrial pollutants causes air pollution and water pollution.

Question 15.
Write preventive measures of sound pollution.
Answer:
Preventive measures of noise pollution:

• Noise pollution can be controlled by designing quieter machines, proper lubrication and better maintenance of machines. Noise producing parts of machines may be covered by suitable insulating materials.
• Noise producing industries should be installed away from residential areas.
• Use of public addressing systems should be restricted at a fixed intensity and hours of the day.
• Stuffing of cotton plugs in the ear or use of ear-muffs and minimize the danger of occupational exposure of noise.
• Trees absorb sound vibrations and thus, reduce the noise pollution. Thus, plantation of trees along highways, establishment of parks help in reducing noise pollution.
• By use of silencer in all automobiles and engines.

Question 16.
Write the effects of noise pollution.
Answer:
Effects of Noise pollution :

• The more acute and immediate effect of noise pollution is impairing of hearing leading to auditory fatigue and may finally lead to deafness.
• Interference with speech communication.
• Noise pollution leads to neurosis, anxiety hypertension, cardiovascular disease, hepatic stress, giddiness.
• Annoyance leading to ill-temper, bickering, mental disorientation and violent behaviour.
• The high intensity of noise pollution can cause blood vessels to contract, skin becomes pale, muscles to contract and adrenaline to be short into blood stream with conse¬quence rise in blood pressure. This ultimately results in tension and nervousness.
• Affects different metabolic activities.

Question 17.
How many types of pollution are there ? Explain in brief.
Answer:
Pollution are of following five types :

1. Air pollution,
2. Noise pollution,
3. Water pollution,
4. Radioactive pollution,
5. Soil pollution.

1. Air pollution: Pyrotechnics’ results in the release of harmful gases like CO₂, CO and SO₂ in the environment which produces various types of diseases in living beings.

2. Noise pollution: Pyrotechnics produces the unwanted sound dumped into the atmosphere leading to health hazards.

3. Water pollution: Pyrotechnics produces some waste materials, on reaching water it causes water pollution.

4. Radioactive pollution: Pollution created due to radioactive substance is called radioactive pollution. Atomic energy centres and bombarding also causes radioactive pollution.

5. Soil pollution: Any change in physical and chemical characteristic of soil due to addition of unwanted substance which adversely affects productivity of soil it termed as soil pollution.

Environmental Issues Long Answer Type Questions

Question 1.
Describe the diseases caused due to radioactive pollution.
Answer:
Following diseases are caused by radioactive pollution:

• Leukaemia and bone cancer: In human beings and other animals, radioactive pollution causes blood and bone cancer.
• Ageing: The reproductive capacity of organisms is decreased due to radioactive
  pollution and ultimately causes ageing.
• Epidemic disease: Radioactive pollution causes the decreased rate of antitoxin production which affects the immune system and results in the production of epidemic diseases.
• Nervous system and sensory cells become irritated.
• Radioactive pollution results skin cancer.
• Mutations also take place due to radioactive pollution.
• Thyroid cancer is also produced due to radioactive iodine.

Question 2.
Burning of crackers spread pollution in the environment. Explain.
Answer:
Explosive substances are used in crackers. Crackers are burned for celebration but it causes many harms to the living organisms. Some of the harm effects of burning of crackers are as follows :

1. Air pollution: It releases harmful gases such as CO₂, CO, SO₂ etc. into the atmosphere. Which causes respiratory diseases.

2. Noise pollution: Burning of crackers produces noise which causes noise pollution which effects our hearing capacity, causes headache, increases heartbeat and blood pressure.

3. Water pollution: Waste of burning of crackers are drained into the pond, river with rainwater or through drain which causes harm to aquatic organisms.

4. Soil pollution: Burning of crackers not only produces smoke of harmful gases but its harmful chemicals mixes with soil and pollute it, which makes the soil sterile and reduced growth of plants.

Question 3.
Write an essay on air pollution.
Answer:
Air pollution : Any change in the composition of air is called pollution. The chief reason of air pollution is the releasing of harmful gas in the environment that affectdur eyes, lungs, skins, heart and brain and’produce various disorders in them. Sources of Air polution:

1. Sources of Water pollution: Following are the chief sources of water pollution:
(a) Human sources :

• Domestic sewage,
• Industrial effluents,
• Agricultural wastes,
• Oil pollution,
• Thermal and nuclear power station.

(b) Natural sources: Water pollution takes place by natural ways like soil erosion, mixing of metallic substances, plant leaves, humus and faecal matter of animals etc.

2. Sources of Air pollution: Following are the chief sources of air pollution:
(a) Human sources:

• Combustion activities,
• Industrial activities,
• Agricultural works,
• Use of solvents,
• Activities concerned with atomic energy.

(b) Natural sources: Volcano and its lava, ash, dust, smoke of forest fire, winds, cyclone. Decomposition of matters in the swamp water and liberation of methane gas and different compounds of hydrogen from forests plants, various pollen grains etc.

(A) Effects of air pollution :

• Air pollutant like SO₂ enter the soft tissues causing drying of the mouth, scratching throat and smarting eyes.
• Hydrocarbons and many other pollutants are responsible for causing cancer.
• Oxides of carbon, sulphur and nitrogen diffuse into the blood stream to combine with haemoglobin causing reduction in its oxygen carrying capacity. CO severely damages cardiovascular system and disturbs psychometry functions.
• P.A.N. inhibits Hill reaction and thus, decreases photosynthetic production of an ecosystem.

Control of Air pollution:  Measures for the control of air pollution :

• Industrial smokes must be filtered before releasing it into the atmosphere.
• Tree plantation should be increased and deforestation prevented.
• Use of automobiles should be minimized which reduce the nitrogen contents in the atmosphere.
• The use of crude fuels should be avoided and use of high quality fuels should be recommended.
• Nuclear explosions should be avoided.
• Legal control of air pollution.
• Plantation of air purifying plants.
• Development of parks and gardens in cities.

Question 4.
Name the major air pollutants and their individual effects.
Answer:
Major air pollutants and their individual effects are as follows :

1. Carbon monoxide: It is highly poisonous gas. On entering blood stream, it combines with hemoglobin to block oxygen transport function. It causes laziness, headache, disturbance of psychometry functions, decrease in visual perception, serious effects on cardiovascular system etc.

2. Sulphur dioxide: The animals and human population when exposed to SO₂, suffer from respiratory diseases. It causes chest constriction, headache, vomiting and death from respiratory ailments.

3. Hydrogen sulphide: Its rotten egg like smell cause nausea, irritation in eyes and throat.

4. Nitrogen oxide: It inhibits cilia action so that soot and dust penetrate far into the lungs and finally resulting respiratory diseases in human beings and animals. In plants, it causing chlorosis.

5. Aerosoles: These are the chemicals affecting ozone layer of the atmosphere due to which UV rays enter in the atmosphere and causing various diseases in plants and animals.

6. Ammonia : It inflame upper respiratory passage in human beings. In plants, it inhibits seed germination, destruction of chloroplast and inhibition of the growth of roots and shoots.

7. Hydrogen chloride: It affects the leaves of the plants, eyes, respiratory organs of animals and human beings.

8. Hydrocarbons: It causes yellowing of plants, drying of buds, whereas in man and other animals, mucous glands of eyes and nose are irritated.

Question 5.
Write down the methods to control soil pollution.
Answer:
Control of Soil pollution: By following methods soil pollution can be prevented:

• Government should make provisions for latrines and people should not be allowed to litter in open fields.
• Solid wastes such as tin, copper, iron, glass etc., should not be dumped into soil.
• The solid wastes should be recycled to form new materials.
• Fertilizers and pesticides should be judiciously used.
• Instead of pesticides to kill pests, biological control methods should be adopted-*
• The excretory waste of man an’d cattle should be used to prepare biogas.
• Clean and well covered dustbins should be used in villages and cities.
• Closed hollow pipes should be used to collect and discharge liquid wastes.
• To prevent soil erosion, grass and small plants should be grown.
• Soil management should be adopted.

Question 6.
What are the sources of soil pollution?
Answer:
Sources of soil pollution:

• Acid rainwater and water from mines are main sources of soil pollution.
• Mixing of debris, waste products with the soil cause soil pollution.
• By excessive use of pesticides and fertilizers, pollute the soil.
• When industrial wastes are discharged in the soil, they also pollute the soil.
• Heavy metals e.g., Cadmium, Zinc, Nickel, Arsenic etc., are mixed with the soil
  from mines. These metals are harmful for plants as well as primary and secondary consumers, in a food chain. ’
• Bones of dead animals, paper putrified flesh and food, iron, copper, mercury etc., pollute the soil.
• In our villages and rural areas, where there are no latrines, people go in fields for being at ease. From their stool also the soil is polluted.
• Insecticides like D.D.T. is very dangerous substance. When these enter the body of consumers from producers, their concentration is increased because these are non-degradable substances. Moreover, these can remain in the atmosphere for upto 15.years.

Question 7.
Explain non-ionising and ionising radiation.
Answer:
Types of Radiations on the basis of their action on cells, radiations are of two types:
1. Non-ionising radiations: These include ultraviolet rays (UV rays; 100-300 nm), these have low penetration capacity. These affect only those cells which absorb them. The cause are as following :

• Sunburn: It includes rupturing of sub-cutaneous blood capillaries, blisters, reddening of skin and injury to stratum germinativum.
• Snow blindness: It damages eyesight due to damage of corneal cells.
• Inactivation of organic bio-molecules arid formation of thymin dimer in DNA.
• However they cause cancer, tumor, skin disease, etc.

2. Ionizing radiations : These include X-rays, cosmic rays and atomic radiations. These radiations have low wavelengths but high penetration power. These damage the living cells shifting the electron from one to other bio-molecule. Their harmful effects are as follows :

• Short range effects: These may appear within few days or a few weeks after exposure. The effects include loss of hair, nails, subcutaneous bleeding, metabolic changes, change in proportion of blood cells, dead tissues or death of the organisms inliigh dose.
• Long range effects: These appear in several months or even several years after their exposure. These cause tumours, cancers, mutations, genetic deformities, shorter life span and developmental defects.

Question 8.
What are sources of noise ’ pollution? Write any four effects of noise pollution.
Answer:
Sources of noise pollution: Noise is either natural such as thunder or man-made. The common sources of noise pollution are :

• Industries such as textile mills, printing-press, engineering establishments, etc.
• Defence equipment and vehicles such as tanks, artillery and rocket launching explosions, practise firing, etc.
• Transport vehicles as trains, trucks, buses, two-wheelers, jet planes, etc. mid accessory noise produced by horns, sirens.
• Other applications as dynamite blasting, use of jack hammers, pile drivers, bulldozer, lawn mowers, etc.

Effects of noise pollution:

• The more acute and immediate effect of noise pollution is impairing of hearing leading to auditory fatigue and may finally lead to deafness.
• Interference with speech communication.
• Noise pollution leads to neurosis, anxiety, hypertension, cardiovascular disease, hepatic stress, giddiness.
• Annoyance leading to ill-temper, bickering, mental disorientation and violent behaviour.
• The high intensity of noise pollution can cause blood vessels to contract, skin becomes pale, muscles to contract and adrenaline to be shot into blood stream with consequence rise in blood pressure. This ultimately results in tension and nervousness.
• Affects different metabolic activities.

Question 9.
What is Green house effect? Write any four impacts of Green house effect
Answer:
Green house effect: The Green house effect may therefore, be defined as “The progressive warming up of the earth’s surface due to blanketting effect of man-made CO₂ in the atmosphere. It means the excessive presence of those gases blocked in the infrared radiation from earth’s surface to the atmosphere leading to an increase in temperature, which in turn would make life difficult on earth to forthcoming future generations.
Four impacts of Green house effects are :

1. Effect on global climate : The climate of earth has never been free of change. Its composition, temperature and self-cleansing ability have all varied since, the planet first formed. Yet the pace in the past two countries has been remarkable. The atmosphere’s composition in particular has changed significantly faster than it has at any time in human history.

Increase in Green house gases does not increase die temperature of the earth i.e„ it is not uniform. Temperature is normal at poles and is very less at tropics. In Iceland, Greenland, Sweden, Norway, Finland, Alaska, Siberia, temperature is more, thus at poles, ice starts melting.

2. Effect of Green house Effect on forests: When the atmospheric temperature increases, only those plants can survive which can bear high temperature. Because of this, new species of plant also come into existence, Herbaceous plant can not survive in this high temperature. Plants with high wood Will increase in number. According to a survey if the a nount of CO₂ in the atmosphere is doubled, there will be a great decrease in a green biomass.

3. Effect on crops: The positive aspect of greenhouse effect will be on agriculture. Because, CO₂ is a natural fertilizer, the plants will grow larger and faster with increasing CO₂ in the atmosphere. At first sight, the abnormal growth of plants might be expected to be beneficial because the yields of major crops might increase, however chances of depletion of characters and productivity of soil are also associated with this.

4. Effect on ozone layer : During depletion, the chlorine, fluorine, or bromine molecules of CFCs and halogens are converted into reactive free radical form by photochemical reactions from their intial non-reactive sites. Oxides of nitrogen generally inactivate Cl but the lowering of stratospheric temperature changes. NO₂ into non-reactive ritric acid. Thus, Cl or F are free to react with ozone, distintegrating it into O₂ + O.

The tiny ice particles during winter favours the conversion of chlorine into chlorine monoxide, which behaves as a catalytic compound. The abundance of chloromonoxide rich air in stratosphere continues to rise. Chlorine monoxide react with nascent oxygen and thereby gets converted into chlorine. Thus, the cycle continues destroying the ozone-level.

MP Board Class 12th Biology Solutions

MP Board Class 12th Biology Solutions Chapter 2 Sexual Reproduction in Flowering Plants

Sexual Reproduction in Flowering Plants NCERT Textbook Questions and Answers

Question 1.
Name the parts of an angiosperm flower in which development of male and female gametophyte take place.
Answer:
Development of male gametophyte takes place in anther and female gametophyte in ovary.

Question 2.
Differentiate between microsporogenesis and megasporogenesis. Which type of cell division occurs during these events? Name the structure formed at the end of these two events.
Answer:
Differences between Microsporogenesis and Megasporogenesis:

No.	Microsporogenesis	Megasporogenesis
1.	In this process haploid microspores are formed from diploid microspore motto’cell.	In this process, haploid megaspores are formed from diploid megaspore mother cell.
2	The four microspores formed from a single microspore mother cell are generally aranged in a tetrahedral structure.	The four megaspores formed from a megaspore mother cell are arranged in die from of a linear tetrad.
3.	All the four microspores arranged in a tetrahedral tetrad are functional.	Only one megaspore remain functional while the other three degenerates.

Meiosis Occurs during micro and megasporogenesis microspores (Pollen grain) are formed at the end of micro sporogenesis and female gametophyte (enibro sac) are formed at the end of megasporogenesis.

Question 3.
Arrange the following terms in the correct developmental sequence:
Pollen grain, sporogenous tissue, microspore tetrad, pollen mother cell, male garnets.
Answer:
Sporogenous tissue → Pollen mother cell → Microspore → Tetrad → Pollen grain → Male garnets.

Question 4.
With a neat, labelled diagram, describe the parts of a typical angiosperm ovule.
Answer:
Structure of Ovule: Each ovule consists of the following parts as visible in a longitudinal section:

• • A small stalk or funicle by which the ovule remains attached with the placenta of the
    ovary.
  • Hilum is the point at which it is attached with the ovule. In inverted ovule the funicle fuses with the main body of the ovule and is called as raphe.
  • The ovule is surrounded on all sides by two integuments but not at the apex where an aperture called micropyle is present. This end of the ovule is called as micropylar, while the end of the ovule opposite to it is called as chalazal end.
  • Embryo sac is situated inside the nucellus.
  • Towards the micropyle end of embryo sac one egg or oospore and two synergids are found, and towards the chalaza end of embryo sac three antipodal cells are found. At the centre secondary nuclei is found.
    

Question 5.
What is mean by monosporic development of a female gametophyte ?
Answer:
Out of theTour megaspores, three degenerate and only one remains funtional which develops in, to a female gametophyte or embryo sac. This is called monosporic development, i.e., when embryosac develops from one single megaspore it is called monosporic embryo sac.

Question 6.
With a neat diagram explain the 7-celled, 8-nucleate nature of the female gametophyte.
Answer:
Explanation: Nucleus of the functional megaspore undergoes mitosis resulting in 2-nuclei that move to two opposite poles forming 2-nucleate embryo sac.
Two more mitotic nuclear divisions result in 4-nucleate and later 8-nucleate stages of the embryo sac. so, far no cytokinesis (cytoplasmic division) has taken place.
Now cell walls start to build leading to the organisation of female gametophyte or embryo sac.

Six of the 8-nuclei are bound by cell wall and the remaining 2-celled polar nuclei lie below the egg apparatus in the large central cell.
Seven-celled stage
Three cells are grouped together at the micropylar end and constitute the egg appara¬tus, which is constituted of two synergids and one egg cell.
Three cells at the chalazal end are called antipodals. The large central cell has 2-polar nuclei.
Thus, a typical angiosperm embryo sac at maturity is 7-celled but 8-nucleated as the central cell has 2-nuclei

Question 7.
What are chasmogamous flowers? Can cross pollination occur in cleistogamous flower ? Give resion for your answer.
Answer:
Chasmogamous flowers are open flowers with exposed stamens and stigma which facilitate cross pollination.
No cross pollination occurs in cleistogamous flowers. As these flowers are closed and never open and thus no transfer of pollen from outside to stigma of the flower is possible. So there are no occurs cross pollination.

Question 8.
Mention two strategies evolved to prevent self-pollination in flowers.
Answer:
Two strategies evolved to prevent self-pollination are :
(i) Pollen release and stigma receptivity is not synchronized.
(ii) Anthers and stigma are placed at such positions that pollen doesn’t reach stigma.

Question 9.
What is self-incompatibility ? Why does self-pollination not lead to seed forma¬tion in self-incompatible species ?
Answer:
Self-incompatibility is a genetic mechanism to prevent self pollen from fertilizing the ovules by inhibiting pollen germination or pollen tube growth in the pistil.
In these cases, self-pollination does not lead to seed formation because fertilization is inhibited.

Question 10.
What is bagging technique? How is it useful in a plant breeding programme?
Answer:
It is the covering of female plant with butter paper or polythene to avoid their contamination from foreign pollens during breeding programme.

Question 11.
What is triple fusion? Where and how does it take place ? Name the nuclei involved in triple fusion?
Answer:
Triple fusion refers to the process of fusion of three haploid nuclei. It takes place in the embryo sac.
The 3-nuclei that fuse together are, nucleus of the male gamete and 2-polar nuclei of the central cell to produce a triploid primary endosperm nucleus.

Question 12.
Why do you think the zygote is dormant for sometime in a fertilized ovule?
Answer:
The zygote is dormant in fertilized ovule for sometime because at this time, endosperm needs to develop. As endosperm is the source of nutrition for the developing embryo, the nature ensures the formation of enouth endosperm tissue before starting the process of embryogenesis.

Question 13.
Differentiate between:
(a) Hypocotyl and Epicotyl
(b) Colcoptile and Coleorhiza
(c) Integument and Testa
(d) Perisperm and Pericarp.
Answer:
(a) Differences between Hypocotyl and Epicotyl:

No.	Hypocotyl	Epicotyl
1.	lies between the radicle and the point lies between the radicle and the point of attachment of colyledons is called hypocotyl.	The region of the embryonal axis that lies between the plumule and cotyledons is called epicotyl.
2.	Hypocotyl pushes the seed above the soil in epigeal germination	Epicotyl pushes the plumule above the soil in hypogeal germination.
3.	It is an important component of embryonic root system.	It is an important component of embryonic shoot system.

(b) Differences between Coleoptile and Coleorhiza:

No.	Coleoptile	Coleorhiza
1.	The shoot apex and few leaf primordia are enclosed in epicotyl region is called coleoptile	The redicle and rootcap are situated at the lower end of embryonal axis are enclosed by protective sheath called coleorhiza.
2	It comes out of the soil.	It remains inside the soil.

(c) Differences Between Integement and Testa:

No.	Integument	Testa
1.	It is the protective covering of the ovule	It is the protective covering of the seed
2.	It is part of pre fertilisation	It is a part of post fertilisation.

(d) Differences between Peris perm and Pericarp:

No.	Perisperm	Pericarp
1.	It is the part of nucellus which remains in	Ovary is convert into pericarp after
2	It is a part that belongs to seed	It is a part that belongs to fruit.
3.	It is usually dry.	It can be dry and fleshy.

Question 14.
Why is apple called a false fruit? Which parts of the flower forms the fruit?
Answer:
Apple is called a false fruit because it develops from the thalamus instead of ovary (thalamus is the enlarged structure at the the base of the flower).

Question 15.
What is meant by emasculation? When and why does a plant breeder employ this technique?
Answer:
Emasculation means removal of anthers, with a forceps, from the flower bud before dehiscence.
Plant breeder employs this technique to prevent contamination of stigma with the undesired pollen. This is useful in artificial hybridisation, where desired pollen is required.

Question 16.
If one can induce parthenocarpy through the application of growth substances, which fruits would you select to induce parthenocarpy and why?
Answer:
Oranges, lemons, lichis could be potential fruits for inducing the parthenocarpy because seedless variety of these fruits would be much appreciated by the consumers.

Question 17.
Explain the role of tape turn in the formation of pollengrain wall.
Answer:
Tapetum is the innermost layer of the microsporangium. It produces the exine layer of the pollen grains, which is composed of the sporopollenin, the most resistant fatty, substance.
During microsporongenesis, the cells of tapetum produce various enzymes, hormones, amino acids and other nutritious material required for the development of pollen grains.

Question 18.
What is apomixis and what is its importance?
Answer:
Apomixis is the process of asexual production of seeds, without fertilisation.
The plants that grow from these seeds are identical to the mother plant.

Uses :

• It is a cost effective method for producing seeds.
• It has great use for plant breeding when specific traits of a plant have to be pre¬served.

Sexual Reproduction in Flowering Plants Other Important Questions and Answers

Sexual Reproduction in Flowering Plants Objective Type Questions

1. Choose the Correct Answers:

Question 1.
Fertilization process is:
(a) Fusion of male gamete with egg
(b) Transference of pollengrains to stigma
(c) Fusion of polar nucleus with male gamete
(d) Formation of seed from ovule.
Answer:
(a) Fusion of male gamete with egg

Question 2.
Female gametophy te of angiosperms is:
(a) Megaspore mother cell
(b) Ovule
(c) Endosperm
(d) Nucellus.
Answer:
(c) Endosperm

Question 3.
Effect of nector demonstrate by Xenia word on:
(a) Morphological tissue
(b) Root
(c) Flower
(d) Endosperm.
Answer:
(d) Endosperm.

Question 4.
In a diploid flowering plant, no. of chromosomes are 12, then 6 chromosomes will be present in:
(a) Cotyledons cells
(b) Endospermic cells
(c) Synergids cells
(d) Leaf cells.
Answer:
(c) Synergids cells

Question 5.
Seed coats of seed after fertilization develop from:
(a) Integuments
(b) Endosperms
(c) Chalaza
(d) Ovule.
Answer:
(a) Integuments

Question 6.
Perispermis:
(a) Degenerative secondary nucleus
(b)Apomixis
(c) Peripheral part of endosperm
(d) Parthenogenesis.
Answer:
(b)Apomixis

Question 7.
Development of ovary into fruit from ovule without fertilization, the process is called:
(a) Parthenio ovule
(b) Apomixis
(c) Pathenocarpy
(d) Parthenogenesis.
Answer:
(c) Pathenocarpy

Question 8.
Mitotic cell division in an ovule takes place in:
(a) Nucellus
(b) Megaspore mother cell
(c) Macrosporangia
(d) Archisporium.
Answer:
(b) Megaspore mother cell

Question 9.
Development of sporophyte without the fusion of a gamete is called:
(a) Apomixis
(b) Apospory
(c) Apogamy
(d) Pollination.
Answer:
(c) Apogamy

Question 10.
Male gametes are found in angiospermic plants :
(a) In pollengrain
(b) In anther
(c) In ovule
(d) All of these
Answer:
(a) In pollengrain

Question 11.
The function of pollentube is:
(a) Help in pollination
(b) Protection of stigma
(c) Male gamete carrier
(d) All of these
Answer:
(c) Male gamete carrier

Question 12.
Tapetum is a part of:
(a) Male gametophyte
(b) Female gametophyte
(c) Ovary wall
(d) Anther wall.
Answer:
(d) Anther wall.

Question 13.
Cotyledons is situated in monocots:
(a) Axial
(b) Terminal
(c) Basal
(d) In Any Position
Answer:
(a) Axial

Question 14.
Which type of pollination found in sunflower:
(a) Self pollination
(b) Cross pollination
(c) All of the above
(d) None of these.
Answer:
(c) All of the above

Question 15.
Endospermic nucleus are :
(a) Haploid
(b) Diploid
(c)Triploid
(d) None of these.
Answer:
(b) Diploid

Question 16.
Double fertilization is discoverd by: :
(a) By Navaschin
(b) Leuwenhock
(c) Strasburger
(d) Hofmeister.
Answer:
(a) By Navaschin

Question 17.
The type of pollination in which genetically different pollen grains are brought to
stigma is : (AMU 2012)
(a) Xenogamy
(b) Geitonogamy
(c) Cleistogamy
(d) Dichogamy. ,
Answer:
(a) Xenogamy

Question 18.
If the number of chromosome in root cell is 14 then what will be the number of chromosome in synergid cell of in ovule of that parent (BHU2012)
(a) 14
(b) 21
(c) 7
(d) 28.
Answer:
(c)7

Question 19.
Presence of many embryo (Polyembryony) is characters tic feature of: (BHU2012)
(a) Citrus
(b) Mango
(c) Banana
(d) None of these.
Answer:
(a) Citrus

Question 20.
Sporopollenin is formed by the polymerisation of : (BHU2012)
(a) Fat and Phenol
(b) Carotenoid and Fat
(c) Fat and Ester
(d) Carotenoid and Ester.
Answer:
(a) Fat and Phenol

2. Fill in the Blanks:

1. The main function of endosperm in a seed is the storage of ………………
2. Pollination takes place by the agency of bird is called ………………
3. Apple is an example of fruit. ………………
4. Tissue on which ovules are attached is called ………………
5. ……………… types stamens are found in sunflower.
6. In plants development of fruit takes place from ………………
7. One cotyledon of maize is called ………………
8. Tetradynamous stamens are found in ………………
9. ………………is thin in endospermic seed.
10. In ovule …………….. is joined with funiculus.
11. Anther is ……………… in angiospermic plants.
12. ……………… type of pollination are found in Typha.
13. ……………… pollination is occurs in Salvia.
14. Outer wall of pollen grain is called ………………
15. Process of seedless fruit is called ………………

Answer:

1. Food material
2. Omithophilly
3. False
4. Placenta
5. Syngenecious
6. Ovary
7. Scutellum
8. Mustard
9. Cell wall
10. Hylum
11. Reproductive organ
12. Joint
13. Insect
14. Exine
15. Parthenocarpy.

3. Match the Following:

Answer:

1. (e)
2. (d)
3. (b)
4. (a)
5. (c)

4. Answer in One Word/Sentence:

1. Name the four whorls of flower.
2. Give the term for plants which produce flower and fruits many times.
3. Name the outer coat of the seed.
4. Give example of plant in which flowers are pollinated by bat.
5. Give the term used for similar calyx and corolla.
6. What parts of the plant produce seed and fruit after fertilization?
7. Name the type of pollination carried out of bat.
8. Give the term for fruit development without fertilization.

Answer:

1. Calyx, Corolla, Androecium and Gynoecium
2. Perrenial plants
3. Seed coat
4. Kadamb
5. Petalloid
6. Ovary
7. Chiropteriphilly
8. Parthenocarpy.

Sexual Reproduction in Flowering Plants Very Short Answer Type Questions

Question 1.
Development of female gametophyte occurs in which cell?
Answer:
By functional megaspore mother cell.

Question 2.
What is the other name of female gametophyte?
Answer:
Embryo sac.

Question 3.
Ovule derives nourishment from which part of the carpel?
Answer:
Ovule derives nourishment from placenta.

Question 4.
What are cleistogamous flowers ? Give an example.
Answer:
The flowers which do not open are called cleistogamous flowers, e.g. Commelina

Question 5.
What is the substance found on the exine of pollen grains?
Answer:
Sparopollenin.

Question 6.
Give the characters of wind pollinated flowers.
Answer:
White in colour, small in size and pollengrains are formed in large number.

Question 7.
What is the ploidy of angiospermic endosperm?
Answer:
Triploid.

Question 8.
Give an example of a monocotyledonous endospermic seed.
Answer:
Ricinus.

Question 9.
Give example of two false fruit.
Answer:
Apple, Jackfruit.

Question 10.
What are monocious plants?
Answer:
Plants which has both male and female flower.

Sexual Reproduction in Flowering Plants Short Answer Type Questions

Question 1.
What is parthenogenesis ?
Answer:
Parthenogenesis : It is the method of reproduction in which ovum develops into embryo and forms a new plant without fertilization. It has been observed that pollination is necessary for parthenogenesis. It stimulates the process. Ulothrix, Spirogyra and Solan- aceae and Malvaceae family plants reproduce by this method.
Sometimes in some plants ovary also develops into fruit during this process. Such fruits are called as parthenocarpic fruits.
Example: Banana, Apple, Grapes, Guava etc. shows parthenocarpic fruits.

Question 2.
What is Polyembryony?
Answer:
Polyembryony : When more than one embryo develops in one seed then this condition is called as Polyembryony. It is generally found in citrus family. It is also found in Nicotiana, conifers, rice, wheat. It occurs when fertilization occurs in all embryo sacs found in the ovule.

Question 3.
Describe structure of anther with labelled diagram.
Answer:
Structure of Anther : Transverse section of anther shows that it consists of 2 lobes which are connected by connective. Each lobe contains two Pollen sacs. Innermost layer of pollen sac is called as Tapetum.

Tapetum is a layer rich in nutritive contents which supplies food material for the developing pollen grains. At first many Pollen mother cells are formed in them which divides meiotically to form haploid pollen grains.

Question 4.
Give four contrivances for self pollination.
Answer:
Contrivances for self-pollination:
(1) Bisexuality : When male and female parts are found in same flower then possibility of self-pollination increases.

(2) Cieistogamy : In Commelina benghalensis both cleistogamous and chasmogamous flowers are produced. The former are the underground flowers and the latter are the aerial ones developed on branches. In the small, inconspicuous cleistogamous flowers the pollen are shed within the closed flowers so that self-pollination is a must. This is also observed in Impatiens, Oxalis, Viola, Portulaca etc.

(3) Homogamy : Here the stamens and carpels mature at the same time. So, there is a greater chance of self-pollination as compared to cross-pollination, e.g., Mirabilis, Argemone etc.

(4) Failure of cross pollination : In some flowers generally cross pollination occurs but if they fails to do cross pollination then self-pollination occurs.

Question 5.
What do you mean by micropropagation?
Answer:
Micropropagation : It is a modern method of reproduction. By this process thousands of new plants can be obtained from few tissues of mother plant. This method is based on tissue and cell culture technique.
In this process a small part of tissue is separated from the plant and then it is grown in nutrient medium in aseptic condition. The tissue develops to form a cluster of cells which is called as callus. This callus can be preserved for long time for multiplication. A small part of the callus is transferred to nutrient medium, where it grows into a new plant. This plant is then transferred to the field. By this process Orchids, Carnations, Chrysanthemum plants can be grown successfully.

Question 6.
What are the advantages of cross-pollination ?
Answer:
Advantages of cross-pollination:

• The weaker characteristics of the race elimi¬nated and replaced by better character of nature.
• New improved varieties cap be produced by cross-pollination. ‘
• It increases the adaptability of the offsprings.
• Seeds are more vigorous.

Question 7.
What is fertilization? Draw labelled diagram showing path of pollen tube during fertilization.
Or
What do you mean by sexual reproduction? Describe the process of fertilization in plants with the help of diagram or sexual reproduction.
Answer:
Fertilization : The process of fusion of male and female gamete is called as fertilization or sexual reproduction. As a result of this process a diploid zygote is formed.

Question 8.
Differences between self and cross pollination
Answer:
Differences between Self and Cross poltination :

No.	Self pollination	Cross pollination
1.	It is the process of transfer of pollen grains from one flower to the stigma of same flower of same plant.	Transfer of pollen grains from one flower to the stigma of flower of another plant.
2.	Medium is not reqired	Medium is required
3.	Plants do not show any special chara cter.	Attractive, coloured,scent or honey bearing flowers are produced to attract insect.
4.	Less number of pollen grains are produced.	More number of pollen grains are produced.

Sexual Reproduction in Flowering Plants Long Answer Type Questions

Question 1.
What is self-pollination ? Give advantages and disadvantages of self pollination.
Answer:
Self-pollination : When the pollen grain of one flower are transferred to the stigma of the same flower then the process is called as self-pollination.

Advantages of self-pollination:
These are the advantages of self pollination:

• Parental characters can be preserved indefinitely in several generations.
• Self-pollination helps in maintaining pure lines for experimental hybridization.
• It is most economical method of pollination. The plants do not consume their energies in the production of
• large number of pollen grains, nectar and coloured corolla.
• It ensures seed production and flowers do not take chances of the failure of fertilization.

Disadvantages of self-pollination:
These are the disadvantages of self-pollination :

• The weaker characteristics or defects of the plant can never be eliminated from the race.
• No useful characters can be introduced in the race.
• The immunity of race towards diseases falls and ultimately it falls prey to many diseases.

Question 2.
What is double fertilization?
Or
Explain double fertilization in angiosperms.
Answer:
Double fertilization : It is found in all angiospermic plants. It was first discovered by S.N. Navaschin (1899) in Lilium and Fritillaria. When pollen tube come in contact of embryo sac then the tip of the pollen tube disintegrate and release two male gametes into the embryo sac. Out of which one male gamete (x) fuses with egg cell (x) to form a diploid zygote. This process is called as fertilization. The second male gamete (x) fuses with secondary nuclei (2x) to form a triploid body.
The act of two nuclear fusion is called as double fertilization.

Question 3.
Describe development of embryo sac or Female gametophyte in angiosperms.
Answer:
Development of embryo sac or Female gametophyte in angiosperms :
During the initial stage of development of ovule primary archesporial cell gets demarcated at the apex of the nucellus below the epidermis. It divides periclinally into a outer primary parietal cell or primary wall cell and an inner primary sporogenous cell. The later acts as a megaspore mother cell which enlarges in size and divide meiotically to form a row of four megaspores. Of the four cells the upper three cells degenerate and appear as dark caps while the lowest one functions arid is called the functional megaspore. The latter greatly enlarges and forms the embryo sac.

Question 4.
Describe development of Endosperm.
Answer:
Development of Endosperm : It develops from the triploid tissue of the fertilized embryo sac after the act of double fertilization. It is of the following three types:

1. Free nuclear endosperm.
2. Cellular type of endosperm.
3. Helobial type of endosperm.

The name refers to the type of nuclear divisions of the endosperm nucleus. If triploid nucleus divides by free nuclear division the endosperm produced contains many nuclei lying freely in it and hence it is termed as free nuclear endosperm. If the nuclear division is followed by wall formation it is called as cellular type. If endosperm is intermediate between the two types it is called as helobial type.


Question 5.
What is male gametogenesis ? Describe male gametogenesis in plants.
Or
Describe development of pollen grain.
Answer:
Male gametogenesis: The process of formation of male gametes is called as male gametogenesis or microsporogenesis.

Each anther usually consists of two lobes, connected together by a connective. Each lobe contains two sacs called as Pollen sac. In the early stage of development the anther comprises of a homogenous mass of cells limited by a well demarcated epidermis. During the course of development the anther gets four lobed. Each lobe exhibits a hypodermal lining, few cells thick with distinct nuclei. These hypodermal cells constitute the archesporium. The cell of archesporium divide periclinally, cutting of parietal cells towards the periphery and sporogenous cells within it two chambers or loculi, which are termed as pollen sacs or microsporangia.

Fig. Development of Pollen grain : (A) Formation of Pollen lobes, (B) Archesporial cell, (C) and (D) Division in Parietal cell, (E) and (F) Parietal layer : Tapetum sporogenous tissue (G), (H) and (I) Pollen mother cell, (J) Pollen grain, (K) Outer layer Degenerate, (L) Four free Pollen grains.

Besides the above changes in the wall layers the sporogenous layer comprising of primary sporogenous cells also undergo several divisions to form microspore mother cells or pollen mother cells. In the initial stage the microspore mother cells are closely packed but as the anther enlarges the pollen sac becomes spacious and the pollen mother cells assume spherical shape and get loosely arranged.

In many cases some of the sporogenous cells are nonfunctional and serve only as the nutritive material for the functional microspore mother cells. Each microspore mother cell is diploid in nature and by a single meiotic division give rise to four haploid nuclei. The four nuclei so formed are arranged tetrahedrally, and called as Tetrad. Innermost layer of pollen sac is called as Tapetum. Outer to which endothecium layer is formed. In outer most layer of pollen sac epidermis is formed. Surrounding each nuclei exine and intine are formed, now each structure is called as Pollen grain. Pollen grains are liberated during the dehiscence of anthers through stomium.

Question 6.
Differenciate between:
(i) Embryo sac and Endosperm
(ii) Seed and Ovule
Answer:
(i) Difference between Embryosac and Endosperm:

No.	Embryo sac	Endosperm
1.	It is haploid structure.	It is triploid structure.
2.	It is found in ovule.	It is found in seed.
3.	It is formed before fertilization.	It is formed after fertilization.
4.	Nutritive materials are stored.	Nutritive materials are not stored.
5.	It consists antipodal cells, egg cell, synergid cells and two polar nuclei.	Antipodal cells, egg cell, synergid cells are absent and all cells are similar.

(ii) Difference between Seed and Ovule

No.	Seed	Ovule
1.	It is formed in the fruit seed is formed after fertilization of ovule.	Before fertilization ovule is found into the ovary called mega sporangium.
2.	Seed is surrounded by integument. Outer covering is called outer integument and inner covering is called inner integument.	Nucellus is present below the ovule and is surrounded by inner and outer covering.
3.	Embryosac is absent in seed.	Embryosac is present in ovule.
4.	Embryo is present in seed	Embryo is absent in ovule.
5.	Endosperm may be found in seed	Endosperm is not found in ovule.
6.	Seed make a new plant	Ovule is not germinate.

MP Board Class 12th Biology Solutions