Free practice › Class 12 › Biology › Chapter 8
Microbes in Human Welfare — NEET MCQs with answers
Chapter 8 explores the beneficial roles of microbes across multiple domains: food and dairy production (LAB, yeast, fungi), industrial fermentation (beverages, antibiotics, enzymes, bioactive molecules), sewage treatment (aerobic and anaerobic microbes reducing BOD), biogas generation (methanogens/Methanobacterium), biological pest control (Bacillus thuringiensis, baculoviruses, Trichoderma), and soil enrichment as biofertilisers (Rhizobium, Azotobacter, cyanobacteria, mycorrhizal fungi).
Topics in this chapter
- 8.1 Microbes in Household Products
- 8.2 Microbes in Industrial Products
- 8.3 Microbes in Sewage Treatment
- 8.4 Microbes in Production of Biogas
- 8.5 Microbes as Biocontrol Agents
- 8.6 Microbes as Biofertilisers
Free practice questions
A notable advantage of using Bacillus thuringiensis over chemical insecticides is that it:
- A. Kills caterpillars but leaves other insects unharmed
- B. Kills all insects in the field
- C. Persists as a toxic residue in soil
- D. Also acts as a weedicide
Show answer
Answer: A — NCERT states the bacterial disease will kill the caterpillars but leave other insects unharmed.
NCERT Class 12 Biology · Ch 8 · 8.5 Microbes as Biocontrol Agents
Which of the following is the correct grouping: 'Anabaena, Nostoc, Oscillatoria' are all ___?
- A. nitrogen-fixing cyanobacteria
- B. mycorrhizal fungi
- C. free-living soil bacteria
- D. symbiotic nodule bacteria
Show answer
Answer: A — NCERT: Anabaena, Nostoc and Oscillatoria are cyanobacteria that can fix atmospheric nitrogen.
NCERT Class 12 Biology · Ch 8 · 8.6 Microbes as Biofertilisers
A small amount of curd added to fresh milk to start the process of curd formation acts as an inoculum or starter because it contains:
- A. Concentrated milk proteins
- B. Vitamin B12 crystals
- C. Baker's yeast spores
- D. Millions of lactic acid bacteria
Show answer
Answer: D — A small amount of curd added to the fresh milk as inoculum or starter contains millions of LAB, which at suitable temperatures multiply, converting milk to curd.
NCERT Class 12 Biology · Ch 8 · 8.1 Microbes in Household Products
In which type of areas is cattle dung available in large quantities?
- A. Metropolitan cities
- B. Rural areas
- C. Coastal ports
- D. Industrial estates
Show answer
Answer: B — NCERT states cattle dung is available in large quantities in rural areas where cattle are used for a variety of purposes.
NCERT Class 12 Biology · Ch 8 · 8.4 Microbes in Production of Biogas
Pectinases and proteases are used in industry to:
- A. Clarify bottled fruit juices
- B. Remove oily stains from laundry
- C. Dissolve blood clots
- D. Lower blood cholesterol
Show answer
Answer: A — NCERT states bottled fruit juices are clarified by the use of pectinases and proteases.
NCERT Class 12 Biology · Ch 8 · 8.2 Microbes in Industrial Products
Why can sewage NOT be discharged directly into natural water bodies like rivers and streams?
- A. It has a very high oxygen content
- B. It is too clean for rivers
- C. It contains only harmless inorganic salts
- D. It contains large amounts of organic matter and pathogenic microbes
Show answer
Answer: D — NCERT states sewage contains large amounts of organic matter and microbes, many of which are pathogenic; before disposal it is treated in STPs to make it less polluting, so it cannot be discharged directly.
NCERT Class 12 Biology · Ch 8 · 8.3 Microbes in Sewage Treatment
When Bt spores are eaten by insect larvae, how does Bacillus thuringiensis kill the larvae?
- A. The spores digest the larval cuticle from outside
- B. The spores paralyse the larval nervous system externally
- C. The bacteria block the larval respiratory pores
- D. The toxin is released in the gut of the larvae
Show answer
Answer: D — NCERT states that in the gut of the larvae, the toxin is released and the larvae get killed.
NCERT Class 12 Biology · Ch 8 · 8.5 Microbes as Biocontrol Agents
Biofertilisers are best defined as organisms that:
- A. produce antibiotics in soil
- B. decompose sewage in treatment plants
- C. enrich the nutrient quality of the soil
- D. kill soil pathogens directly
Show answer
Answer: C — NCERT states 'Biofertilisers are organisms that enrich the nutrient quality of the soil.'
NCERT Class 12 Biology · Ch 8 · 8.6 Microbes as Biofertilisers
The specificity in texture, flavour and taste among cheese varieties like Swiss and Roquefort is primarily governed by:
- A. The shape of the mould tray
- B. The amount of vitamin B12 added
- C. The colour of the milk
- D. The different microbes used in ripening
Show answer
Answer: D — The specificity of each cheese's texture, flavour and taste comes from the microbes used: the bacterium Propionibacterium sharmanii gives Swiss cheese its large holes, and a specific fungus ripens Roquefort cheese.
NCERT Class 12 Biology · Ch 8 · 8.1 Microbes in Household Products
Cyclosporin A is to organ transplantation as statins are to:
- A. Oily-stain removal
- B. Clot busting
- C. Blood cholesterol lowering
- D. Juice clarification
Show answer
Answer: C — NCERT states cyclosporin A is used as an immunosuppressant in organ transplant, and statins are used to lower blood cholesterol.
NCERT Class 12 Biology · Ch 8 · 8.2 Microbes in Industrial Products
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