Chapter 10: Microbes in Human Welfare

Q1. How are microbes used in sewage treatment?

Solution

Primary treatment: Physical removal of floating debris
Secondary treatment: Microbes decompose organic matter aerobically
Tertiary treatment: Chemical/physical purification for recycling

Q2. What is biogas? Name the bacteria involved in its production.

Solution

Biogas is a mixture of methane, CO₂, and H₂S produced by anaerobic decomposition of organic matter.

Methanogens: Methanobacterium - produce methane (CH₄)

Q3. What are the uses of Lactobacillus in daily life?

Solution

1. Conversion of milk to curd (lactic acid fermentation)
2. Production of cheese and yogurt
3. Probiotic supplements for gut health

Q4. What is mycorrhiza? How does it benefit the plant?

Solution

Benefits: (1) Increased absorption of minerals (especially P) (2) Drought resistance (3) Protection from pathogens

Q5. What are biocontrol agents? Give examples.

Solution

Examples: (1) Trichoderma - controls plant pathogens (2) Bacillus thuringiensis - kills insect pests (3) Ladybird beetles - controls aphids (4) Nuclear polyhedrosis virus - kills insects

Q6. What are biofertilizers? Name three types.

Solution

Types: (1) Bacteria - Rhizobium, Azotobacter (2) Fungi - Mycorrhiza (3) Cyanobacteria - Anabaena, Nostoc

Q7. What are the industrial products obtained from microbes?

Solution

1. Antibiotics (Penicillin from Penicillium)
2. Organic acids (Citric acid from Aspergillus)
3. Enzymes (Lipase, Pectinase)
4. Bioactive molecules (Streptokinase, Cyclosporin A)
5. Ethanol
6. Statins

Q8. What are the steps in conversion of milk to curd?

Solution

1. Lactobacillus added to warm milk
2. Bacteria convert lactose to lactic acid
3. Acid lowers pH, casein coagulates
4. Milk solidifies to form curd
5. Diacetyl develops flavor

Q9. What are the roles of microbes in household products?

Solution

1. Curd - Lactobacillus
2. Bread - Yeast (Saccharomyces)
3. Idli/Dosa - Leuconostoc, Streptococcus
4. Cheese - Lactobacillus, Streptococcus
5. Toddy - Natural fermentation by yeasts

Q10. What is the process of biogas production?

Solution

Components: (1) Digester tank (2) Mixing tank (3) Gas holder (4) Outlet tank
Process: Hydrolysis → Acidogenesis → Acetogenesis → Methanogenesis

Q11. What is Streptokinase?

Solution

Medical use: (1) Clot buster (2) Removes blood clots from coronary arteries (3) Treats myocardial infarction

Q12. What is Cyclosporin A?

Solution

Produced by Trichoderma polysporum
Uses: (1) Immunosuppressant (2) Used during organ transplant (3) Prevents rejection (4) T-lymphocyte inhibitor

Q13. What are the advantages of biofertilizers over chemical fertilizers?

Solution

1. Environmentally friendly
2. Cost-effective
3. Renewable and sustainable
4. Do not cause soil pollution
5. Improve soil structure

Q14. What is the role of cyanobacteria in agriculture?

Solution

1. Fix atmospheric nitrogen (Anabaena, Nostoc)
2. Biofertilizers in paddy fields
3. Add organic matter to soil
4. Some used as food (Spirulina)

Q15. What are the applications of microbes in environmental management?

Solution

1. Sewage treatment (biodegradation)
2. Bioremediation (oil spills, heavy metals)
3. Biogas production (waste to energy)
4. Biocontrol (reducing pesticide use)
5. Composting

← Chapter 9: Strategies for Enhancement in Food Production Chapter 11: Biotechnology: Principles and Processes →

← All Class 12 Biology Chapters