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NCERT - Microbes in Human Welfare Questions and Answers of Class 12 Biology | GkSeries

31 Semiconservative replication of DNA was first demonstrated in
1 Salmonella typhimurium
2 Drosophila melanogaster
3 Escherichia coli
4 Streptococcus pneumoniae

Answer: Escherichia coli
32 A sewage treatment process in which a part of decomposer bacteria present in the wastes is recycled into the starting of the process is called
1 Primary treatment
2 Activated sludg0e treatment
3 Cyclic treatment
4 Tertiary treatment

Answer: Activated sludg0e treatment


33 The symbiotic association of fungi with the roots of higher plants is called:
1 Eubacteria
2 Actinomycetes
3 Mycorrhiza
4 None of these

Answer: Mycorrhiza
34 Monascus purpureus is a yeast used commercially in the production of
1 Citric acid
2 Blood cholesterol lowering statins
3 Ethanol
4 Streptokinase for removing clots from the blood vessels

Answer: Blood cholesterol lowering statins
35 Bacterial leaf blight of rice is caused by a species of:
1 Envinia
2 Pseudomonas
3 Alternaria
4 Xanthomonas

Answer: Xanthomonas
36 A symbiotic relationship/interaction in which 'one species benefits and the other species is not affected' is called:
1 Ectomycorrhizae
2 Endomycorrhizae
3 Commensalism
4 Helotism

Answer: Commensalism
37 Powdery mildew of wheat is caused by a species of
1 Ustilago
2 Erysiphe
3 Puccinia
4 Albugo

Answer: Erysiphe
38 Which of the following is added to milk to curdle it or produce fermented milk products?
1 Azotobacter
2 Lactobacillus
3 Rhizobium
4 Clostridium

Answer: Lactobacillus
39 Crop rotation is used by farmers to increase
1 Organic content of soil
2 Nitrogenous content of soil
3 Soil fertility
4 All of these

Answer: Soil fertility
40 Agriculture by using only biofertilizers is called
1 Manuring
2 Composting
3 Inorganic farming
4 Organic farming

Answer: Organic farming
41 Which of the followings is also called sac fungi that live parasitically and in various habitats?
1 Basidiomycetes
2 Zygomycetes
3 Ascomycetes
4 Basidiomycetes

Answer: Ascomycetes
42 Two microbes found to be very useful in genetic engineering are
1 Diplococcus sp. and Pseudomonas sp.
2 Vibrio cholerae and a tailed bacteriophage
3 Escherichia coli and Agrobacterium tumefaciens
4 Crown gall bacterium and Caenorhabditis elegans

Answer: Escherichia coli and Agrobacterium tumefaciens
43 The most important of the symbiotic nitrogen fixing bacteria which forms nodules on the roots of legume plants is
1 Aspergillus
2 Rhizobium
3 Penicillium
4 Streptococcus

Answer: Rhizobium
44 Some hyperthermophilic organisms that grow in highly acidic (pH2) habitats belong to the two groups
1 Liverworts and yeasts
2 Eubacteria and archaea
3 Cyanobacteria and diatoms
4 Protists and mosses

Answer: Eubacteria and archaea
45 One of the free-living anaerobic nitrogen-fixer is
1 Azotobacter
2 Beijerinckia
3 Rhodospirillum
4 Rhizobium

Answer: Rhodospirillum

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