Which of the following statements is/are incorrect?
(i) Cyanobacteria are autotrophic microbes widely distributed in aquatic and terrestrial habitats.
(ii) Anabaena, Nostoc and Oscillatoria are photosynthetic N₂-fixing cyanobacteria.
(iii) Tolypothrix (BGA) can increase rice production by about 20%.
(iv) BGA adds organic matter to the soil and increase its fertility.
(v) In our country, biofertilisers are not available commercially in the markets for farmers.

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Important Questions on Microbes in Human Welfare

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IMPORTANT

MTG OBJECTIVE NCERT AT YOUR FINGERTIPS BIOLOGY CLASS XI + XII>Chapter 33 - Microbes in Human Welfare>MCQS CORNER>Q 100

Match Column I with Column II and select the correct answer from the given codes.

	Column I		Column II
$(a)$	Azolla	$(i)$	Symbiotic N₂- fixer
$(b)$	Rotenone	$(i i)$	Symbiotic association with N₂- fixing cyanobacteria
$(c)$	Crotalaria juncea	$(i i i)$	Natural insecticide
$(d)$	Frankia	$(i v)$	Green manure

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MTG OBJECTIVE NCERT AT YOUR FINGERTIPS BIOLOGY CLASS XI + XII>Chapter 33 - Microbes in Human Welfare>HOTS HIGHER ORDER THINKING SKILLS>Q 1

Which of the following curves correctly represent the process of antibiotic production by the Streptomyces species?

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MTG OBJECTIVE NCERT AT YOUR FINGERTIPS BIOLOGY CLASS XI + XII>Chapter 33 - Microbes in Human Welfare>HOTS HIGHER ORDER THINKING SKILLS>Q 2

In a microbiology laboratory, the technician uses heat to sterilize the nutrient solution that is used to grow a fungus. When the heating system broke down, he sterilized the solution by passing it (in a sterile environment) through a sterile filter with a pore size of

0.2

micrometers. When the fungus was grown in the filtered nutrient solution, it stopped growing and looked unhealthy within a few days. Which statement is the most likely explanation for the observed effects on the fungus?

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MTG OBJECTIVE NCERT AT YOUR FINGERTIPS BIOLOGY CLASS XI + XII>Chapter 33 - Microbes in Human Welfare>HOTS HIGHER ORDER THINKING SKILLS>Q 3

Study the given differences between primary sludge and activated sludge and select the incorrect ones.

	Primary sludge	Activated sludge
(i)	It is sludge formed during primary sewage treatment.	It is sludge formed during secondary sewage treatment.
(ii)	It possesses flocs of decomposer microbes.	It does not possess flocs of decomposer microbes.
(iii)	It does not require aeration.	Formation of activated sludge requires aeration.
(iv)	A lot of decomposition occurs during formation of primary sludge.	Very little decomposition occurs during formation of activated sludge.