Chapter 10: Microbes in Human Welfare – Short Answer Type Questions
CBSE Class 12 Biology Short Answer Questions (NCERT): Microbes in Human Welfare
Course & Examination Details
- Course: CBSE Class 12 Biology
- Unit: Unit III – Biology and Human Welfare
- Chapter: Chapter 10 – Microbes in Human Welfare
- Prescribed Textbook: NCERT Biology Class XII
- Examination: CBSE Class 12 Board Examination
- Question Type: Short Answer Type
- Answer Length: 60–80 words
- Syllabus Alignment: Strictly as per NCERT
Section A: Microbes in Household Products
Q1. Explain the role of Lactobacillus in curd formation.
Answer:
Lactobacillus converts lactose present in milk into lactic acid. This acid coagulates milk proteins, forming curd. The process improves digestibility, enhances flavour, increases vitamin B12 content, and inhibits growth of harmful microbes.
Q2. How is fermentation useful in household food preparation?
Answer:
Fermentation improves taste, texture, and nutritional quality of foods like idli, dosa, and bread. Microbes produce organic acids and gases that enhance digestibility and food value.
Q3. Why are fermented foods considered healthy?
Answer:
Fermented foods contain beneficial microbes that improve gut health, increase vitamin content, enhance digestion, and suppress disease-causing organisms.
Q4. Describe the role of yeast in bread making.
Answer:
Yeast ferments sugars in dough to produce carbon dioxide, causing the dough to rise and making bread soft and fluffy.
Q5. Name two traditional Indian fermented foods and microbes involved.
Answer:
Curd uses Lactobacillus, while idli batter uses lactic acid bacteria and yeast.
Section B: Microbes in Industrial Products
Q6. What are antibiotics? Give one example.
Answer:
Antibiotics are chemical substances produced by microorganisms that inhibit or kill disease-causing microbes. Penicillin produced by Penicillium is a classic example.
Q7. Explain industrial production of antibiotics.
Answer:
Antibiotics are produced in large-scale bioreactors using selected microbial strains under controlled conditions, followed by purification.
Q8. How are alcoholic beverages produced using microbes?
Answer:
Yeast ferments sugars into ethanol and carbon dioxide to produce beverages like wine and beer. Distillation yields spirits like whisky and rum.
Q9. Describe the industrial use of organic acids produced by microbes.
Answer:
Microbes produce organic acids like citric acid and acetic acid, widely used as food preservatives, flavouring agents, and in pharmaceuticals.
Q10. What are bioactive molecules? Give examples.
Answer:
Bioactive molecules are microbial products affecting human physiology. Examples include statins and cyclosporin A.
Q11. Explain the role of statins.
Answer:
Statins lower blood cholesterol levels by inhibiting cholesterol synthesis, reducing risk of heart diseases.
Q12. How does cyclosporin A help in medicine?
Answer:
Cyclosporin A acts as an immunosuppressant, preventing organ transplant rejection.
Q13. Why are microbial enzymes preferred in industries?
Answer:
They are efficient, specific, biodegradable, and work under mild conditions, making them eco-friendly.
Q14. Explain the use of enzymes in detergents.
Answer:
Proteases, lipases, and amylases break down protein, fat, and starch stains, enhancing cleaning efficiency.
Q15. What is the role of bioreactors in industrial microbiology?
Answer:
Bioreactors provide optimal conditions for large-scale microbial growth and product formation.
Section C: Microbes in Sewage Treatment
Q16. What is sewage and why must it be treated?
Answer:
Sewage is wastewater containing organic matter and pathogens. Treatment prevents pollution and disease spread.
Q17. Describe primary sewage treatment.
Answer:
Primary treatment involves physical removal of large particles through filtration and sedimentation.
Q18. Explain secondary sewage treatment.
Answer:
Secondary treatment uses aerobic microbes to degrade organic matter, significantly reducing BOD.
Q19. What are flocs and their significance?
Answer:
Flocs are microbial aggregates that digest organic matter during sewage treatment.
Q20. Define BOD and its significance.
Answer:
BOD measures organic matter in water. Lower BOD indicates cleaner water.
Q21. What is activated sludge?
Answer:
Activated sludge is microbial biomass settled after secondary treatment.
Q22. Explain anaerobic sludge digestion.
Answer:
Anaerobic bacteria digest sludge producing biogas and reducing pathogens.
Q23. How does sewage treatment protect aquatic ecosystems?
Answer:
It prevents discharge of untreated waste, reducing pollution and protecting aquatic life.
Section D: Microbes in Biogas Production
Q24. What is biogas?
Answer:
Biogas is a renewable fuel produced by anaerobic digestion of organic waste by microbes.
Q25. Name microbes involved in biogas production.
Answer:
Methanogenic bacteria like Methanobacterium are involved.
Q26. Describe stages of biogas production.
Answer:
Stages include hydrolysis, acidogenesis, and methanogenesis.
Q27. Why is biogas considered eco-friendly?
Answer:
It is renewable, reduces pollution, and utilises waste efficiently.
Q28. What is the use of biogas slurry?
Answer:
It is used as nutrient-rich organic manure.
Section E: Microbes as Biocontrol Agents
Q29. What is biological control?
Answer:
Biological control uses living organisms to control pests and pathogens.
Q30. Explain the role of Bacillus thuringiensis in pest control.
Answer:
It produces toxins that kill insect larvae, acting as a biopesticide.
Q31. How do Trichoderma species act as biocontrol agents?
Answer:
They suppress soil-borne plant pathogens and protect crops.
Q32. Name two advantages of biocontrol.
Answer:
Biocontrol is eco-friendly and reduces chemical pesticide use.
Q33. Give an example of a predator used in biocontrol.
Answer:
Ladybird beetle controls aphids.
Section F: Microbes as Biofertilisers
Q34. What are biofertilisers?
Answer:
Biofertilisers are microbes that enhance soil fertility by nutrient enrichment.
Q35. Explain the role of Rhizobium.
Answer:
Rhizobium fixes atmospheric nitrogen in leguminous plants, improving soil fertility.
Q36. How do free-living nitrogen fixers benefit crops?
Answer:
They fix nitrogen independently, enriching soil nitrogen content.
Q37. Describe the role of cyanobacteria as biofertilisers.
Answer:
Cyanobacteria fix nitrogen in paddy fields, improving soil fertility.
Q38. What is mycorrhiza?
Answer:
Mycorrhiza is a symbiotic association between fungi and plant roots.
Q39. State benefits of mycorrhiza to plants.
Answer:
It enhances phosphorus uptake, drought tolerance, and disease resistance.
Q40. Why are biofertilisers considered eco-friendly?
Answer:
They improve soil health without chemical pollution.
Section G: Integrated & Exam-Oriented
Q41. How do microbes support sustainable agriculture?
Answer:
They act as biofertilisers and biocontrol agents, reducing chemical input.
Q42. Why is microbial sewage treatment important for public health?
Answer:
It removes pathogens and organic pollutants, preventing disease spread.
Q43. Explain the significance of probiotics.
Answer:
Probiotics improve gut health and boost immunity.
Q44. How do microbes contribute to waste management?
Answer:
They decompose organic waste through sewage treatment and biogas production.
Q45. Why is biogas technology important in rural areas?
Answer:
It provides renewable energy and organic manure.
Q46. How do industrial microbes contribute to economy?
Answer:
They produce valuable products like antibiotics, enzymes, and acids.
Q47. Distinguish between biocontrol and chemical control.
Answer:
Biocontrol is eco-friendly, while chemical control causes pollution.
Q48. Why is Chapter 10 important for CBSE exams?
Answer:
It covers applied microbiology frequently asked in exams.
Q49. Mention one environmental benefit of microbes.
Answer:
They reduce pollution through waste treatment.
Q50. Summarise the role of microbes in human welfare.
Answer:
Microbes support food production, medicine, agriculture, and environmental protection.
✔ Strictly NCERT-Based | ✔ CBSE Board Aligned | ✔ Ideal for 3–4 Mark Questions