Class 8 Science
Microorganisms: Friend and Foe
Q.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 of __________. (d) Cholera is caused by __________.
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Q.2
Tick the correct answer:
(a) Yeast is used in the production of
(i) sugar
(ii) alcohol
(iii) hydrochloric acid
(iv) oxygen
(b) The following is an antibiotic
(i) Sodium bicarbonate
(ii) Streptomycin
(iii) Alcohol
(iv) Yeast
(c) Carrier of malaria-causing protozoan is
(i) female Anopheles mosquito
(ii) cockroach
(iii) housefly
(iv) butterfly
(d) The most common carrier of communicable diseases is
(i) ant
(ii) housefly
(iii) dragonfly
(iv) spider
(e) The bread or idli dough rises because of
(i) heat
(ii) grinding
(iii) growth of yeast cells
(iv) kneading
(f) The process of conversion of sugar into alcohol is called
(i) nitrogen fixation
(ii) moulding
(iii) fermentation
(iv) infection
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Q.4
Can microorganisms be seen with the naked eye? If not, how can they be seen?
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Q.5
What are the major groups of microorganisms?
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Q.6
Name the microorganisms which can fix atmospheric nitrogen in the soil.
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Q.7
Write 10 lines on the usefulness of microorganisms in our lives.
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Q.8
Write a short paragraph on the harms caused by microorganisms.
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Q.9
What are antibiotics? What precautions must be taken while taking antibiotics?
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