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NCERT Solutions for Class 8th Science


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Chapter 2. Microorganisms : Friend And Foe

Additional Questions With Solutions




Additional Questions With Solutions

Q1: What are the major groups of microorganisms?

Ans: (i) Bacteria (ii) Fungi  (iii) Protozoa  (iv) algae

Q2: What are viruses?

Ans: Viruses are also microscopic. But they reproduce only inside the cells of the host organism, which may be bacteria, plant and animals etc. common cold influenza and cough are caused by viruses.

Q3: Name three diseases caused by virus.

Ans: Polio, chicken pox and measles.

Q4: Name three water born diseases.

Ans: Hepatitis, typhoid, cholera etc. 

Q5: How do microorganisms help us.


Write the uses of microorganisms for various purposes.

Ans:  The uses of microorganisms:-

(i)  They are used in the preparation of curd, bread and cake.

(ii) They are also used in cleaning up of the environment.

(iii) They are used in the preparation of medicines.

(iv) They are used to increase soil fertility by fixing nitrogen.

Q6: Name the microorganism which is found in curd.

Ans: Lactobacillus bacteria.

Q7: Name the bacteria which promote the formation of curd.

Ans: Lactobacillus.

Q8: What is fermentation?

Ans: The process of conversion of sugar of fruits juice into alcohol is known as fermentation.

Q9: Name the gas produced by yeast during the process of fermentation.

Ans: Carbon dioxide.

Q10: Name the microorganism which is used for large scale production of alcohol.

Ans: Yeast.

Q11: What is food poisoning? What is its disadvantages. 

Ans: Food poisoning could be due to the consumption of food spoilt by some microorganisms. Microorganisms that grow on our food sometimes produce toxic substances. These make the food poisonous causing serious illness and even death.

Q12: What are antibiotics?

Ans: The medicines which kill or stop the growth of the disease causing bacteria such medicines are called antibiotics. Ex . streptomycin, penicillin and erythromycin etc.

Q13: Name two antibiotics.


(i) Streptomycin.

(ii) Penicillin


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