NEET Biology Microbes in Human Welfare MCQs Set 06

Answer: (b) Trichoderma

Explanation:
1. Trichoderma is a free-living fungus found in root ecosystems and is effective against many plant pathogens.
2. Baculoviruses and NPV attack insects and arthropods, and ladybird beetles eat aphids while dragonflies eat mosquitoes.

Teacher's Note:
1. Trichoderma is used as a biofungicide. It acts on soil-borne pathogens and is safe for the environment.

Answer: (d) All of the above

Explanation:
1. Different strains of Bt give toxins that kill particular insects.
2. Strains act against lepidopteran larvae (moths and butterflies), flies and mosquitoes, so all three are controlled.

Teacher's Note:
1. Bt toxins are specific to the group of insects that have the matching gut receptors. Bt cotton protects against bollworms.

Answer: (a) Glomus

Explanation:
1. Glomus is a fungus that forms mycorrhiza with plant roots and absorbs phosphorus from the soil for the plant.
2. Azotobacter is free living, and Trichoderma and Aspergillus do not form such a symbiosis.

Teacher's Note:
1. Mycorrhizal fungi such as Glomus supply phosphorus and water, resist root pathogens and tolerate salinity. The plant gives them carbohydrates.

Answer: (c) Both IARI and KVIC

Explanation:
1. The Indian Agricultural Research Institute (IARI) and the Khadi and Village Industries Commission (KVIC) developed the technology in India.
2. WHO is not involved.

Teacher's Note:
1. Remember both names together: IARI and KVIC. Biogas plants use cattle dung slurry in a digester tank, with a floating gas holder to collect the gas.

Answer: (d) Statins – Cholesterol lowering agent

Explanation:
1. Aspergillus niger gives citric acid, not acetic acid.
2. Streptokinase is a clot buster and cyclosporin A is an immunosuppressive agent, so options 2 and 3 are swapped.
3. Statins from Monascus purpureus lower blood cholesterol by inhibiting the enzyme that makes cholesterol, so option 4 is correct.

Teacher's Note:
1. Bioactive molecules: cyclosporin A (immunosuppressant), statins (cholesterol-lowering) and streptokinase (clot buster in myocardial infarction).

Answer: (c) Bioinsecticides and bioherbicides

Explanation:
1. Biopesticides are living organisms or their products used to control pests.
2. They include bioinsecticides and bioherbicides (and biofungicides). Biofertilisers supply nutrients and are not pesticides.

Teacher's Note:
1. Biopesticides kill or suppress pests and weeds. Biofertilisers are a different group because they improve soil nutrition.

Answer: (a) Aphids

Explanation:
1. Ladybird beetles are predators of aphids.
2. Dragonflies control mosquitoes, and bollworm is controlled by Bt.

Teacher's Note:
1. Predators like ladybird are used in integrated pest management. They reduce the need for chemical pesticides.

Answer: (c) Methanogenic bacteria

Explanation:
1. In the digester, cattle dung is broken down anaerobically and methanogenic bacteria produce methane.
2. Viruses do not carry out fermentation, and algae and fungi are not the gas producers.

Teacher's Note:
1. Methanogens are anaerobic and are found in the rumen of cattle too. Their activity produces the CH₄ and CO₂ mixture called biogas.

Answer: (a) Yeast

Explanation:
1. Baker's yeast ferments sugar in the dough and releases CO₂.
2. The gas bubbles make the dough rise and the bread porous.

Teacher's Note:
1. Dough is left to rise because Saccharomyces cerevisiae produces CO₂. The same fermentation in an alcoholic drink gives ethanol.

Answer: (a) Anabaena

Explanation:
1. Anabaena is a filamentous cyanobacterium that fixes nitrogen both as a free-living form and as a symbiont of Azolla.
2. Chlorella is a green alga and Rhizobium is a symbiotic bacterium of legume roots.

Teacher's Note:
1. Anabaena azollae lives inside Azolla leaves and gives nitrogen to the fern. Azolla is used in paddy fields as a green manure.

Answer: (a) Ethanol

Explanation:
1. Yeast ferments sugars to ethanol and CO₂.
2. Methanol and acetic acid are not its products, and antibiotics such as penicillin come from Penicillium.

Teacher's Note:
1. Brewer's yeast produces wine and beer (no distillation) and whisky, brandy, rum (with distillation). Baker's yeast makes bread rise.

Answer: (b) Saccharomyces cerevisiae

Explanation:
1. Saccharomyces cerevisiae (baker's yeast) is used to leaven bread.
2. Rhizopus stolonifer is the bread mould, which spoils bread.

Teacher's Note:
1. Do not confuse the bread mould (Rhizopus) with the baker's yeast. The mould spoils bread, while the yeast makes it rise.

Answer: (d) Bacillus thuringiensis

Explanation:
1. Bacillus thuringiensis produces insecticidal protein crystals and is the common microbial insecticide.
2. The other bacilli are not used as insecticides.

Teacher's Note:
1. B. thuringiensis is the source of Bt toxin, which is also used in transgenic crops.

Answer: (c) Acetobacter aceti

Explanation:
1. Acetobacter aceti oxidises ethanol to acetic acid (vinegar).
2. Clostridium butylicum gives butyric acid, and Bacillus and Azotobacter are not used for vinegar.

Teacher's Note:
1. Acetobacter aceti converts alcohol to acetic acid in the presence of oxygen. This is an oxidation, so it is not a true anaerobic fermentation.

Answer: (c) Aspergillus niger

Explanation:
1. Aspergillus niger is a fungus that ferments sugar to citric acid.
2. Lactobacillus gives lactic acid, and the other two fungi are not the industrial source of citric acid.

Teacher's Note:
1. Organic acids: citric acid (Aspergillus niger), acetic acid (Acetobacter aceti), butyric acid (Clostridium butylicum) and lactic acid (Lactobacillus).