Microbes in Human Welfare - NEET Previous Year Questions with Complete Solutions

Yes. For this chapter specifically, NCERT Class 12 Biology is completely sufficient. Every NEET question from this chapter in the last 10 years has been answerable directly from the NCERT text, tables, or diagrams. No additional reference book is needed — but you must read NCERT carefully, not skim it

The highest-frequency topics are: organism-product pairs (antibiotics, statins, organic acids), sewage treatment stages and BOD, biogas production and methanogens, and biofertilisers like Rhizobium and Azolla. Biocontrol agents — especially Bacillus thuringiensis and baculoviruses — have also appeared repeatedly in recent years.

NEET typically includes 2–4 questions from this chapter every year. Based on analysis of papers from 2013 to 2024, the chapter has appeared in every single NEET paper. This makes it one of the most reliable scoring chapters in Biology, especially because the questions are factual and directly from NCERT Class 12.

Biocontrol agents are living organisms used to control pests and pathogens — examples include Bacillus thuringiensis (controls insect larvae) and Trichoderma (controls plant fungal diseases). Biofertilisers are microorganisms that enrich soil nutrients, especially by fixing atmospheric nitrogen — examples include Rhizobium, Nostoc, and mycorrhiza. Both replace harmful chemicals but serve different agricultural functions.

Methanogens are strict anaerobic bacteria that produce methane (biogas) by breaking down organic matter. In nature, they are found in the rumen (gut) of cattle and in marshy areas. In biogas plants, they act on cattle dung slurry to produce methane, CO₂, and H₂S. Methanobacterium is the key organism to remember for NEET.

BOD stands for Biochemical Oxygen Demand. It measures the amount of dissolved oxygen needed by aerobic microorganisms to break down organic matter in a water sample. A high BOD means the water is heavily polluted. NEET tests this concept as part of the sewage treatment process — specifically the secondary (biological) treatment stage.