Home › NEET Biology MCQs › Microbes in Human Welfare
NEET · Biology · Class 12

Microbes in Human Welfare — NEET Biology MCQs

30 questions written by hand against the NCERT chapter. Every wrong option is explained, not just the right one.

30questions
10/14/6easy / medium / hard
₹0no login
Take the Microbes in Human Welfare test →
Free · your all-India rank after you finish

Sample questions from this chapter

Warm milk inoculated with a spoonful of curd thickens and gains vitamin B₁₂. Which microbial activity caused this?
  1. Lactic acid bacteria produced acid that coagulated and partly digested milk proteins ✓
  2. Methanogens converted milk to methane
  3. Viruses lysed casein into ethanol
  4. Rhizobium fixed nitrogen in the milk
Answer: A. Starter curd supplies millions of LAB that multiply at suitable temperature and acidify milk. The acid changes protein texture while the culture improves nutritional quality.
Why not B: Methanogens act anaerobically on cellulosic wastes and do not make curd.
Why not C: Curd formation is bacterial acid fermentation, not viral lysis or alcoholic fermentation.
Why not D: Rhizobium associates with legume roots and is not a dairy starter.
Why is air pumped into secondary-treatment tanks?
  1. To float primary sludge for collection
  2. To suppress useful bacteria
  3. To support vigorous aerobic flocs that consume organic matter ✓
  4. To make methanogens produce oxygen
Answer: C. Mechanical agitation and aeration expand bacterial-fungal flocs, accelerating oxidation of organic load and lowering BOD. Oxygen is the resource for this biological stage.
Why not A: Primary solids are removed earlier by settling.
Why not B: Aeration promotes rather than suppresses the useful aerobic community.
Why not D: Methanogens are anaerobic and produce methane, not oxygen.
Samples A, B and C have BOD values of 400, 20 and 8 mg/L respectively. They represent one untreated sewage inflow, one relatively clean river and one secondary-treatment discharge. Which assignment is most reasonable?
  1. A is raw municipal inflow; B is the river; C is processed discharge ✓
  2. The treatment-plant discharge is A, with raw sewage at B and river water at C
  3. River = A; secondary effluent = B; untreated inflow = C
  4. The measurement cannot rank biodegradable organic pollution
Answer: A. Untreated sewage has extreme demand; biological treatment lowers it substantially. Given the stated relatively clean river, 20 versus 8 depends local context, but the exercise's intended ordering assigns the lowest to treated discharge.
Why not B: Treatment should reduce rather than leave the maximum oxygen demand.
Why not C: Untreated sewage has the greatest organic load, not the lowest.
Why not D: BOD is specifically an indirect measure of biodegradable organic matter.

These are 3 of the 30 questions in the test. Take the full chapter test →

Read the chapter first

Every NCERT question in this chapter is solved, free: NCERT solutions — Microbes in Human Welfare →

Other NEET Biology chapters

The Living WorldBiological ClassificationPlant KingdomAnimal KingdomMorphology of Flowering PlantsAnatomy of Flowering Plants

All 32 chapters →

Questions

How many NEET questions are there on Microbes in Human Welfare?

This chapter test has 30 questions — 10 easy, 14 medium and 6 hard — all written against the NCERT Class 12 chapter.

Is this NEET Biology chapter test free?

Yes. Every chapter test is free with no login, and you get your all-India rank on every one. Nothing on the site is on sale right now.

Do the questions explain the wrong options?

Yes — every distractor carries its own explanation naming the specific misconception that makes a student pick it. That is the part most question banks skip, and it is the part that changes your next attempt.