Study Materials

NCERT Solutions for Class 8th Science


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Chapter 2. Microorganisms : Friend And Foe

Text Book Exercise




Text Book Exercise 

Q4: Can microorganisms be seen with the naked eye? If not, how can they be seen?

Ans :  No, we cannot see microorganisms with unaided eyes. They can be seen with the help of a microscope.

Q5: What are the major groups of microorganisms?

Ans:  bacteria, protozoa, fungi and some algae are the major group of microorganism.

Q6: Name the microorganisms which can fix atmospheric nitrogen in the soil.

Ans: These are Rhizobium, Azobacter, blue green algae.

Q7: Write 10 lines on the usefulness of microorganisms in our lives.


Q8: Write a short paragraph on the harms caused by microorganisms.


(i) Many infectious or communicable disease like tuberculosis, cholera, plague, flue, chicken pox are caused by microorganism.

(ii) Many protozoa cause disease like malaria, filaria, amoebiasis etc.

(iii) Funguses are causative organisms of many skin diseases.

(iv) Dengue and polio like dangerous diseases are caused by virus like microorganisms.

(v) Several microorganisms harm crops like vegetables, fruits and grains.

Q9: What are antibiotics? What precautions must be taken while taking antibiotics?

Ans: The medicines which kill or stop the growth of the disease-causing microorganisms. Such medicines are called antibiotics.


(i) It must be taken under advised of a qualified doctor.

(ii) Body may develop resistance when we take it unnecessary.

The course of antibiotic must be completed.          


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