CBSE Class 12 Biology – Microbes in Human Welfare

NCERT-aligned chapter resource | Biology Code 044

1. Microbes Around Us

Microorganisms are used in food production, industrial processes, sewage treatment, medicine and agriculture. Their usefulness depends on their metabolic activities.

2. Household Products

Lactic acid bacteria help convert milk into curd. Yeast performs fermentation in bread and beverage production. These examples demonstrate how controlled microbial activity produces useful products.

3. Industrial Products

Microbes produce compounds such as organic acids, alcohols, antibiotics and enzymes. Fermenters provide controlled conditions for large-scale production.

4. Antibiotics

Penicillin was obtained from Penicillium and became a major antimicrobial drug. Antibiotics act against susceptible microorganisms and should not be confused with medicines effective against viruses.

5. Sewage Treatment

Microbial communities in secondary treatment degrade organic matter and reduce biochemical oxygen demand.

6. Biogas

Anaerobic microbes, especially methanogens, produce biogas from organic material. Methane is the major combustible component.

7. Biofertilisers

Microorganisms such as Rhizobium, cyanobacteria and mycorrhizae can improve nutrient availability or plant growth.

8. Biocontrol

Biological control uses living organisms or their products to suppress pests and pathogens, reducing reliance on chemical pesticides in suitable contexts.

Chapter-Specific MCQs

1. Curd formation is strongly associated with: (A) Lactobacillus (B) Plasmodium (C) Rhizobium only (D) HIV. Answer: A.
2. Methanogens are important in: (A) biogas production (B) bread only (C) DNA fingerprinting (D) vaccination. Answer: A.
3. Secondary sewage treatment is mainly: (A) biological (B) purely physical (C) nuclear (D) genetic. Answer: A.

Competency Questions

1. Why does secondary sewage treatment reduce BOD?
2. Explain why methanogens require anaerobic conditions.
3. Choose an appropriate microbial application for a given agricultural or industrial problem and justify it.