Extra Questions for Class 12 Biology Chapter 10 Microbes in Human Welfare

Extra Questions for Class 12 Biology Chapter 10 Microbes in Human Welfare

Q.1. Name the pests that ladybird, beetle and dragonflies help to get rid of.
Ans. Ladybird, beetle and dragonflies control aphids and mosquitoes respectively.

Q.2. Why is distillation required for producing certain alcoholic drinks?
Ans. Distillation increases the alcohol content in alcoholic drinks.

Q.3. What are biofertilisers? Give two examples.
Ans. Biofertilisers are organisms that enrich the nutrients in the soil. e.g. Rhizobium, Azotobacter.

Q.4. The excreta of cattle does not contain any cellulose but human excreta may contain cellulose. Why?
Ans. The rumen of cattle contains methanogens which help in the digestion of cellulose but these bacteria are not present in human stomach so cellulose is not digested.

Q.5. Give an example of a rod-shaped virus.
Ans. Tobacco mosaic virus.

Q.6. What would have happened if antibiotics were not discovered?
Ans. If antibiotics were not discovered, bacterial diseases would not have been controllable.

Q.7. What causes doughing of wheat flour?
Ans. Production of CO₂ gas during yeast fermentation of bacteria.

Q.8. What for Nucleopolyhedroviruses are being used nowadays?
Ans. Nucleopolyhedroviruses are used for the biological control of insect pests.

Q.9. Why are antibiotics always sold in combination with Lactobacillus?
Ans. Antibiotics may kill even the useful bacteria present in the digestive tract. LAB is given, which will protect some microbes in the digestive tract and enhance the production and absorption of vitamin B12.

Q.10. How is the presence of cyanobacteria in the paddy fields beneficial to rice crop?
Ans. Cyanobacteria can fix atmospheric nitrogen. In paddy fields, the cyanobacteria act as an important biofertiliser. They also add organic matter to soil and increase its fertility.

Q.11. Mention the role of cyanobacteria as a biofertiliser.
Ans. It is a biological organism that fixes atmospheric nitrogen.

Q.12. Write the scientific name of the microbe used for fermenting malted cereals and fruit juices.
Ans. Saccharomyces cerevisiae.

Q.13. Give the scientific name of the source organism from which the first antibiotic was produced.
Ans. Penicillium notatum

Q.14. Why are drinks like Whisky and Rum more intoxicating than wine?
Ans. This is because wine is produced without distillation whereas whisky and rum are produced by distillation of the fermented broth.

Q.15. Mention the information that the health workers derive by measuring BOD of a water body.
Ans. (i) By measuring BOD of a water body, health workers find the amount of dissolved oxygen in water. The lesser the amount of dissolved oxygen, the more polluted the water body will be.
(ii) It is also measure of organic matter present in water and uptake of O₂ by microbes.

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