MP Board Class 8th Science Solutions Chapter 2 Microorganisms: Friend and Foe

MP Board Class 8th Science Microorganisms: Friend and Foe NCERT Textbook Exercises

Mp Board Class 8 Science Chapter 2 Question 1.
Fill in the blanks:
(a) Microorganisms can be seen with the help of a ……….. .
(b) Blue green algae fix ………….. directly from air to enhance fertility of soil.
(c) Alcohol is produced with the help.
(a) microscope
(b) nitrogen
(c) yeast
(d) bacteria.

Mp Board Class 8 Science Solution Chapter 2 Question 2.
Tick the correct answer:
(a) Yeast is used in the production of:
(i) Sugar
(ii) Alcohol
(iii)Hydrochloric acid
(iv) Oxygen
(ii) Alcohol

(b) The following is an antibiotic
(i) Sodium bicarbonate
(ii) Streptomycin
(iii) Alcohol
(iv) Yeast
(ii) Streptomycin

(c) Carrier of malaria-causing protozoan is
(i) Female Anopheles mosquito
(ii) Cockroach
(iii) Housefly
(iv) Butterfly
(i) Female Anopheles mosquito

(d) The most common carrier of communicable diseases is
(i) Ant
(ii) Housefly
(iii) Dragonfly
(iv) Spider
(ii) Housefly

(e) The bread or idli dough rises because of
(i) Heat
(ii) Grinding
(iii)Growth of yeast cells
(iv) Kneading
(iii)Growth of yeast cells

(f) The process of conversion of sugar into alcohol is called
(i) Nitrogen fixation
(ii) Moulding
(iii) Fermentation
(iv) Infection

Mp Board Class 8 Science Solution Question 3.
Match the organisms in Column A with their action in Column B.

(i) Bacteria (a) Fixing nitrogen
(ii) Rhizobium (b) Setting of curd
(iii) Lactobacillus (c) Baking of bread
(iv) Yeast (d) Causing malaria
(v) A protozoan (e) Causing cholera
(vi) A virus (f) Causing AIDS
(g) Producing antibodies


(i) Bacteria (e) Causing cholera
(ii) Rhizobium (a) Fixing nitrogen
(iii) Lactobacillus (b) Setting of curd
(iv) Yeast (c) Baking of bread
(v) A protozoan (d) Causing malaria
(vi) A virus (f) Causing AIDS

Class 8 Science Chapter 2 Mp Board Question 4.
Can microorganisms be seen with the naked eye? If not, how can they be seen?
No, we cannot see microorganisms with unaided eyes. They can be seen with the help of a microscope.

Mp Board Class 8 Science Solution English Medium Question 5.
What are the major groups of microorganisms?
The major groups of microorganisms are bacteria, protozoa, fungi and some algae.

Mp Board Class 8 Science Solution In English Question 6.
Name the microorganisms which can fix atmospheric nitrogen in the soil.
They are Rhizobium, Azobactor, blue-green algae such as Anabaena and Nostoc, etc.

Mp Board Class 8th Science Solution Question 7.
Write 10 lines on the usefulness of microorganisms in our lives.
The usefulness of microorganisms in our lives is given below:

  1. Lactobacillus, a bacterium, is useful in the formation of curd.
  2. Microorganisms like bacteria are also involved in the making of breads, cheese, etc.
  3. They are also used in cleaning up of the environment.
  4. Bacteria are also used in agriculture to increase soil fertility by fixing nitrogen.
  5. Microorganisms like yeast are used for the production of alcohol since ages.
  6. They are used in making manure.
  7. Vaccines are made on a large scale from micro-organisms to protect humans and other animals from several diseases.
  8. Several antibiotics are made from micro-organisms.
  9. Some microorganisms are used to make preservatives.
  10. About 50% of atmospheric carbon dioxide is fixed by micro-organisms (algae).

Mp Board 8th Class Science Solutions Question 8.
Write a short paragraph on the harmful effects of microorganisms.
Some micro-organisms are harmful and cause diseases. The harms caused by microorganisms are as follows:

  1. Many communicable diseases, such as cholera, common cold, chickenpox, Tuberculosis (T.B.), etc., are caused by micro-organisms.
  2. Malaria is caused by a micro-organism called Plasmodium carried by female Anopheles mosquito.
  3. Aedes mosquito acts as carrier of dengue virus.
  4. Anthrax is a dangerous human and cattle disease Caused by a bacterium called Bacillus anthracis.
  5. Several microorganisms cause diseases in plants like wheat, rice, potato, sugarcane, orange, apple and others and reduce the yield of the crops.
  6. Food poisoning is also caused by microorganisms, making food poisonous by producing toxic substance in the food.

Mp Board Solution Class 8 Science Question 9.
What are antibiotics? What precautions must be taken while taking antibiotics?
Antibiotics. The medicines which kill or stop the disease causing microorga¬nisms are called antibiotics. The common antibiotics produced from bacteria and fungi are penicillin, streptomycin and tetracycline etc.

The precautions to be taken in using antibiotics are as follows:

  1. Antibiotics should be taken only on the advice of a qualified doctor.
  2. One must finish the course prescribed by the doctor.
  3. If antibiotics are taken when not needed, the bacteria in the body will develop resistance to them. Next time, when you need antibiotics they would be less effective.
  4. The source of these medicines is micro-organisms.

MP Board Class 8th Science Microorganisms: Friend and Foe NCERT Extended Learning – Activities and Projects

Class 8 Science Solution Mp Board Question 1.
Pull out a gram or bean plant from the field. Observe its roots. You will find round structures called root nodules on the roots. Draw a diagram of the root and show the root nodules.
Do yourself.

Mp Board Class 8 Science Solutions Question 2.
Collect the labels from the bottles of jams and jellies. Write down the list of contents printed on the labels.
Ingredients: Sugar, mixed fruit pulp, gelling agent (E440), and acidity regulator (E330). Permitted synthetic food colour (E122) and added artificial flavours. Contains permitted class-II preservatives (E211, E224).

Mp Board Science Solution Class 8 Question 3.
Visit a doctor. Find out why antibiotics sltotdd not be overused? Prepare a short report.
Antibiotics should not be overused because they reduce the power of immunity system. Regular or frequent use make the drug ineffective when needed in future.
They kill beneficial bacteria in our body. So, antibiotics should be consumed only when prescribed by a doctor only.

Class 8 Mp Board Science Solution Question 4.
Project: Requirements – 2 test tubes, marker pen, sugar, yeast powder, 2 balloons and lime water.
Take two test tubes and mark them A and B. Clamp these tubes in a stand and fill them with water leaving some space at the top. Put two spoonful of sugar in each of the test tubes. Add a spoonful of yeast in test tube B. Inflate the two balloons incompletely. Now tie the balloons on the mouths of each test tube.
Keep them in a warm place, away from sunlight. Watch the setup every day for next 3-4 days. Record your observations and think of an explanation. Now take another test tube filled 1/4 with lime water. Remove the balloon from test tube B in such a manner that gas inside the balloon does not escape. Fit the balloon on the test tube and shake well. Observe and explain.
The balloon in test tube B will get inflated because the process of fermentation has taken place in test tube B. Yeast, bacteria and carbon dioxide gas produced during this process has inflated the balloon. Now the balloon will get a little deflated as gas is consumed by the lime water and the lime water will turn milky.
Mp Board Class 8 Science Chapter 2

MP Board Class 8th Science Microorganisms: Friend and Foe NCERT Additional Important Questions

A. Short Answer Type Questions

Mp Board Solution Science Class 8 Question 1.
How Can you see microorganisms?
They can be seen with the help of microscope. These microorganisms are magnified to different extent and then can be seen clearly.

Class 8 Science Mp Board Solution Question 2.
Which microorganisms can be seen with the naked eye?
Common mushrooms are the microorganisms which can be seen with naked eyes.

Mp Board Class 8 Social Science Solution Chapter 2 Question 3.
What are the major groups of microorganisms?
There are five major groups of microorganisms. These groups are bacteria, fungi, protozoa, algae and viruses.

Mp Board 8th Class Science Question 4.
What are the two groups of organisms in fungi?
The two groups of organisms in fungi are yeast and mould. Yeast are usually are unicellular while moulds are multicellular. Moulds also have filament like appearance.

B. Long Answer Type Questions

Class 8 Science Chapter 2 MP Board Question 5.
Are microorganisms always helpful to us? What are their harmful effects?
No, microorganisms are not always helpful to us. They are harmful also causing sickness, cold, malaria, skin infection, influenza and many other diseasses by the action of certain microorganisms. They also spoil food materials and other materials used at home.

Science Class 8 Mp Board Question 6.
Explain Aerobic and Anaerobic bacteria. How do these bacteria reproduce?
Those bacteria that require oxygen for their growth are called Aerobic bacteria. Those bacteria that grow without oxygen are called Anaerobic bacteria.
Bacteria normally reproduce by binary fission under favourable conditions. Sexual reproduction is also observed in these bacteria.

Class 8th Mp Board Science Question 7.
Name some bacteria which are helpful?

  1. Lactobacillus which is a bacterium turns milk into curd.
  2. Bacteria are also involved in the making of cheese, pickles and many other food items.
  3. Bacteria which decompose dead leaves and animals and thus return the carbon, nitrogen and other nutrients to the environment for the next cycle of life processes.
  4. Some friendly bacteria scavenge as well as renew the life giving properties of the soil, water and air.

Question 8.
How do viruses reproduce?
Viruses have their own genetic material but they do not have a cellular structure nor metabolic activity of their own. Viruses use the energy of the host cell and change their machinery in such a way they start producing more viral genes. As they multiply and grow in numbers, the host cell eventually bursts releasing all the virale cells.

MP Board Class 8th Science Solutions