NEET Biology Microbes in Human Welfare MCQs Set 16

Answer: (b) A floating cover is placed over the slurry, which keeps on rising as the gas is consumed in the tank

Explanation:
1. In a biogas plant the floating cover rises as gas is produced and collects under it, and it falls as gas is used.
2. Statement (b) reverses this, so it is incorrect.
3. Hence option (b) is correct: A floating cover is placed over the slurry, which keeps on rising as the gas is consumed in the tank

Teacher's Note:
1. The floating cover rises because gas collects under it, not because gas is consumed.
2. It falls again as the gas is used.

Answer: (d) More than one option is correct

Explanation:
1. Cactoblastis cactorum controls prickly pear cactus and Phytophthora palmivora controls milkweed vine in citrus orchards.
2. Both are bioherbicides, so more than one option is correct.
3. Hence option (d) is correct: More than one option is correct

Teacher's Note:
1. A bioherbicide is a living organism used to kill weeds.
2. Cactoblastis (an insect) controls prickly pear and the fungus Phytophthora palmivora controls milkweed vine.

Answer: (b) Oscillatoria – Increase alkalinity of soil

Explanation:
1. Oscillatoria decrease alkalinity of soil called reclamation of soil.
2. Hence option (b) is correct: Oscillatoria – Increase alkalinity of soil

Teacher's Note:
1. Oscillatoria is a cyanobacterium that reduces the alkalinity of soil and so reclaims usar land.
2. It does not increase alkalinity.

Answer: (c) For controlling plant diseases and pests, chemicals like insecticides and pesticides should be used extensively

Explanation:
1. The organic farmers do not use insecticides and pesticides chemicals.
2. Hence option (c) is correct: For controlling plant diseases and pests, chemicals like insecticides and pesticides should be used extensively

Teacher's Note:
1. Organic farmers avoid heavy use of chemical pesticides.
2. They keep pests at manageable levels through natural checks and balances.

Answer: (b) F T F T

Explanation:
1. Organic farming produces crops rich in proteins.
2. Hence option (b) is correct: F T F T

Teacher's Note:
1. Organic farming uses biofertilisers and avoids chemical fertilisers and pesticides.
2. It does not specially raise lipids and iron, so A and C are false.

Answer: (b) a(iii), b(iv), c(i), d(ii)

Explanation:
1. Saccharomyces cerevisiae is used for commercial ethanol (iii).
2. Monascus purpureus gives blood-cholesterol lowering statins (iv), Trichoderma polysporum gives the immunosuppressant cyclosporin A (i) and Propionibacterium sharmanii ripens Swiss cheese (ii).
3. Hence option (b) is correct: a(iii), b(iv), c(i), d(ii)

Teacher's Note:
1. Yeast gives ethanol, Monascus gives statins, Trichoderma gives cyclosporin A and Propionibacterium gives Swiss cheese.
2. Learn microbe, product and use together as one set.

Answer: (a) Cycas

Explanation:
1. B.G.A. are also found in coralloid roots of Cycas for nitrogen-fixation e.g. Nostoc & Anabaena.
2. Hence option (a) is correct: Cycas

Teacher's Note:
1. Cyanobacteria such as Nostoc and Anabaena live in the coralloid roots of Cycas.
2. They fix nitrogen for the plant.

Answer: (d) Methane, hydrogen sulphide, carbon dioxide

Explanation:
1. Biogas – Methane (CH₄), hydrogen sulphide (H₂S), carbon dioxide (CO₂).
2. Hence option (d) is correct: Methane, hydrogen sulphide, carbon dioxide

Teacher's Note:
1. Biogas from sewage digestion is mainly methane with carbon dioxide and hydrogen sulphide.
2. Oxygen and sulphur dioxide are not formed in anaerobic digestion.

Answer: (c) Estimating the amount of organic matter in sewage water

Explanation:
1. Measuring Biochemical Oxygen Demand (BOD) is a method used for estimating the amount of organic matter present in sewage water.
2. Hence option (c) is correct: Estimating the amount of organic matter in sewage water

Teacher's Note:
1. BOD measures the oxygen used by microbes to break down organic matter in water.
2. It is a measure of the organic load of sewage.

Answer: (c) Trichoderma sp. against certain plant pathogens

Explanation:
1. Trichoderma species are fungi that control certain plant pathogens, so this is biological control using a microbe.
2. Bt cotton is a GM crop, the ladybird is an insect predator and the Nucleopolyhedrovirus is used against insect pests, not white rust.
3. Hence option (c) is correct: Trichoderma sp. against certain plant pathogens

Teacher's Note:
1. Trichoderma is a fungus used against plant pathogens, so it is a true microbial biocontrol agent.
2. Bt cotton is a genetically modified crop, and the ladybird beetle is an insect, not a microbe.

Answer: (a) Biological process

Explanation:
1. Secondary sewage treatment is mainly a biological process.
2. Hence option (a) is correct: Biological process

Teacher's Note:
1. Secondary treatment lets aerobic microbes in flocs digest the organic matter.
2. It is therefore a biological process.

Answer: (b) Saccharomyces

Explanation:
1. Ethanol is commercially produced through Saccharomyces.
2. Hence option (b) is correct: Saccharomyces

Teacher's Note:
1. Saccharomyces cerevisiae (brewer's yeast) ferments sugar to ethanol.
2. This is used in the production of alcohol and beverages.

Answer: (a) (B) and (C) only

Explanation:
1. Organic farming uses only natural inputs such as compost, and it does not use chemical pesticides and urea, so statements B and C are correct.
2. Use of GM crops (A) is not part of it.
3. Hence option (a) is correct: (B) and (C) only

Teacher's Note:
1. Organic farming uses only natural inputs like compost and avoids pesticides and chemical fertilisers.
2. GM crops like Bt cotton are not part of it.

Answer: (a) Trichoderma

Explanation:
1. Trichoderma is a free-living fungus that controls several plant diseases.
2. Baculovirus and Bt control insects, and Glomus is a biofertiliser.
3. Hence option (a) is correct: Trichoderma

Teacher's Note:
1. Trichoderma is a fungal biocontrol agent used against plant diseases.
2. Baculovirus and Bt act on insects, and Glomus is a mycorrhiza.

Answer: (a) Snail

Explanation:
1. Glomus (mycorrhiza), Oscillatoria (cyanobacterium) and earthworms (detritivores) are used in organic farming.
2. Snails are pests, so they are not used.
3. Hence option (a) is correct: Snail

Teacher's Note:
1. Glomus and Oscillatoria are biofertilisers and earthworms are used in organic farming.
2. A snail is a pest and is not used.

Answer: (c) Xanthomonas campestris

Explanation:
1. Trichoderma harzianum, NPV and Bt are biopesticides.
2. Xanthomonas campestris is a pathogenic bacterium that causes black rot of crucifers.
3. Hence option (c) is correct: Xanthomonas campestris

Teacher's Note:
1. Xanthomonas campestris is a plant pathogen that causes black rot.
2. The others are biopesticides.

Answer: (a) Coliforms – Vinegar

Explanation:
1. Vinegar is formed by Acetobacter aceti, not by coliforms, so (a) is wrongly matched.
2. Methanogens make gobar gas, yeast makes ethanol and Streptomycetes make antibiotics.
3. Hence option (a) is correct: Coliforms – Vinegar

Teacher's Note:
1. Vinegar is made by acetic acid bacteria (Acetobacter).
2. Coliforms are gut bacteria that indicate faecal pollution, not vinegar producers.