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Free Download as PDF of the detailed solutions for class 12 Biology from NCERT or CBSE text book as per exam pattern, to help you in day to day learning. We provide all important questions and answers from chapter Microbes in Human Welfare of Biology.
31
Semiconservative replication of DNA was first demonstrated in
[1]
Salmonella typhimurium
[2]
Drosophila melanogaster
[3]
Escherichia coli
[4]
Streptococcus pneumoniae
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
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
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
37
Powdery mildew of wheat is caused by a species of
[1]
Ustilago
[2]
Erysiphe
[3]
Puccinia
[4]
Albugo
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
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
40
Agriculture by using only biofertilizers is called
[1]
Manuring
[2]
Composting
[3]
Inorganic farming
[4]
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
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
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
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