NEET Biology Microbes in Human Welfare MCQs Set 14

Answer: (a) Aspergillusniger

Explanation:
1. Citric acid is commercially produced by the fungus Aspergillus niger through fermentation.
2. Lactobacillus makes lactic acid, Saccharomyces produces ethanol and Clostridium butylicum produces butyric acid.

Teacher's Note:
1. A. niger gives citric acid and gluconic acid.
2. Learn the acid produced by each microbe.

Answer: (d) Trichodermapolysporum

Explanation:
1. Cyclosporin A, an immunosuppressive agent used in organ transplants, is produced by the fungus Trichoderma polysporum.
2. Monascus purpureus yields statins, which lower blood cholesterol.

Teacher's Note:
1. Cyclosporin A stops rejection of transplanted organs.
2. Statins come from Monascus.

Answer: (c) (ii) (i) (iv) (iii)

Explanation:
1. Clostridium butylicum produces butyric acid, Trichoderma polysporum produces cyclosporin A, Monascus purpureus yields blood cholesterol lowering statins and Aspergillus niger produces citric acid.
2. The matching is a-ii, b-i, c-iv, d-iii.

Teacher's Note:
1. Link each microbe with its commercial product.
2. Statins are competitive inhibitors of HMG-CoA reductase.

Answer: (a) Activated sludge

Explanation:
1. After primary treatment, the effluent undergoes secondary treatment, in which the settled bacterial flocs, called activated sludge, are partly returned to the aeration tank and the remaining part is pumped to anaerobic sludge digesters.
2. There anaerobic bacteria digest the sludge and produce biogas.

Teacher's Note:
1. Activated sludge goes to anaerobic digesters.
2. The effluent from the settling tank is released into water bodies.

Answer: (d) Species-specific and inactive on non-target organisms EE

Explanation:
1. A biocontrol agent used in integrated pest management should be species-specific and inactive on non-target organisms, so that it controls only the pest without harming other species.

Teacher's Note:
1. Biocontrol is based on narrow-spectrum, specific agents.
2. Broad-spectrum chemicals harm useful organisms.

Answer: (c) They grow aerobically and breakdown cellulose- rich food.

Explanation:
1. Methanogens are anaerobic archaebacteria which are found in the rumen of cattle and its excreta, break down cellulose-rich food and produce methane for biogas.
2. They do not grow aerobically, so the third statement is incorrect.

Teacher's Note:
1. Methanogens are strict anaerobes.
2. Methanobacterium is the common biogas organism.

Answer: (c) Cyanobacteriaand Rhizobium

Explanation:
1. Cyanobacteria such as Nostoc and Anabaena fix nitrogen and Rhizobium forms root nodules in legumes, so both are used as biofertilisers.
2. Aspergillus and Rhizopus are fungi used in fermentation, not as biofertilisers.

Teacher's Note:
1. Biofertilisers include Rhizobium, Azotobacter, Azospirillum, cyanobacteria and mycorrhiza.
2. They enrich soil nutrients.

Answer: (b) (ii) (iv) (iii) (v)

Explanation:
1. Lactobacillus converts milk to curd, Saccharomyces cerevisiae is used for bread making, Aspergillus niger produces citric acid and Acetobacter aceti produces acetic acid.
2. The correct option is a-ii, b-iv, c-iii, d-v.

Teacher's Note:
1. Cheese is made by Propionibacterium and other microbes.
2. Brewer's yeast is Saccharomyces cerevisiae.

Answer: (a) Trichoderma

Explanation:
1. Trichoderma is a free-living fungus used as a biocontrol agent against plant pathogens.
2. Chlorella and Anabaena are photosynthetic microbes, and Lactobacillus is used for curd formation.

Teacher's Note:
1. Trichoderma controls plant diseases.
2. Bacillus thuringiensis and Baculovirus control insects.

Answer: (b) it has obligate association with mycorrhizae.

Explanation:
1. The Pinus seed cannot germinate and establish without a fungal association because it has an obligate association with mycorrhizae, which help the plant to absorb water and minerals.

Teacher's Note:
1. Mycorrhiza is a symbiosis between a fungus and plant roots.
2. The fungus gets carbohydrates and the plant gets minerals and water.

Answer: (b) statin

Explanation:
1. Statins, produced by the yeast Monascus purpureus, are commercially used as blood cholesterol lowering agents because they inhibit the enzyme HMG-CoA reductase.
2. Cyclosporin A is an immunosuppressant, streptokinase a clot buster and lipases are used in detergents.

Teacher's Note:
1. Streptokinase from Streptococcus dissolves blood clots.
2. Statins reduce cholesterol.

Answer: (b) Trichoderma,Baculovirus,Bacillusthuringiensis

Explanation:
1. Trichoderma (fungus), Baculovirus and Bacillus thuringiensis are all biocontrol agents.
2. Tobacco mosaic virus and aphids are pests, and Oscillatoria, Rhizobium and Azospirillum are biofertilisers.

Teacher's Note:
1. Biocontrol agents attack pests or pathogens.
2. Nucleopolyhedrovirus is an insect pathogen.

Answer: (c) Mutualism

Explanation:
1. Mycorrhizae are mutualistic associations of fungi with the roots of higher plants, in which both partners benefit.
2. They are not examples of amensalism, antibiosis or fungistasis.

Teacher's Note:
1. Mycorrhiza is a mutualism.
2. The fungus gets sugars while the plant gets phosphorus and water.

Answer: (a) Petroleum industry

Explanation:
1. BOD measures the oxygen consumed by microbes to oxidise biodegradable organic matter.
2. Effluents from the petroleum industry contain many non-biodegradable hydrocarbons and toxic compounds, so BOD is not a good index of pollution for such water.

Teacher's Note:
1. BOD reflects only biodegradable organic load.
2. Sugar and dairy wastes are rich in biodegradable matter.