CBSE Class 12 · Biology
Microbes in Human Welfare
Official NCERT chapter from Biology (book code lebo1). ExamMaster notes are original teaching at CBSE Class 12 depth.
This lesson follows the official chapter “Microbes in Human Welfare” in Biology. The words below are ExamMaster’s teaching, not a paste from the book. Use the NCERT chapter for the classroom sequence; use these notes to hold the idea without copying exercises or figures.
- CBSE Class 12
- Medium level
- 8 concepts
1Microbes in Household Products
Household products: curd, dough, a named ferment as taught — a microbe-job in the kitchen. Household is a use, not “all germs”. One Lactobacillus-look if named is enough.
A pathogen-scare as the whole household heading is a miss.
Figure. Curd and steamed batter are not generic 'useful microbes'. Lactobacillus acidifies milk; yeast raises dough. Name the job.
How it works
- Name the taught food-jobThe use.
- Keep the microbe as the workerThe who.
- Refuse a scare as this headingA welfare-job.
2Microbes in Industrial Products
Industrial products: antibiotics, enzymes, a named drink-or-acid as taught. Industry is a tank-job, not a brand-ad. One antibiotic-sentence is enough.
A household curd labelled industry is a skip of scale.
Figure. An industrial figure is a named culture and a named product — ethanol from yeast, penicillin from Penicillium — not a cartoon factory.
How it works
- Name the taught tank-productThe use.
- Keep the microbe as the workerThe who.
- Refuse a brand-adA job.
3Microbes in Sewage Treatment
Sewage treatment: microbes that clean a water-look as taught — BOD if named. Sewage is a clean-job, not a scare. One two-stage mention is enough if the lesson split them.
A drinking-water dump as the leftover sewage-science is a miss.
Figure. Primary settling is physical. The aeration tank is where flocs cut BOD. Part of the sludge returns; the rest is not 'clean water' yet.
How it works
- Name the clean-jobSewage treatment.
- Keep BOD as the extra if taughtHonest.
- Refuse a scare-posterA job.
4Microbes in Production of Biogas
Biogas: a methane-look from a taught mix of microbes. Biogas is a fuel-job, not a fossil-story. One digester-sentence is enough.
A petrol-pump labelled biogas is a miss.
Figure. A biogas plant is a closed anaerobic tank. Methanogens make the gas; spent slurry is manure. The dome is a holder, not the microbe.
How it works
- Name the methane-jobBiogas.
- Keep the microbe-mix as the whoThe worker.
- Refuse a petrol-swapA ferment-fuel.
5Microbes as Biocontrol Agents
Biocontrol: a microbe (or its leftover) that checks a pest as taught. Biocontrol is a check-job, not a poison-manual. One named case is enough.
A chemical spray labelled biocontrol because it “kills pests” is a miss.
Figure. Biocontrol names who eats or infects whom: Bt crystals kill larva; a ladybird takes aphids. The crop box is the job that remains.
How it works
- Name the taught check-jobBiocontrol.
- Keep a microbe as the whoThe worker.
- Refuse a spray-recipeThis class.
6Microbes as Biofertilisers
Biofertilisers: microbes that help a plant’s nutrient-look as taught — Rhizobium if named. Biofertiliser is a help-job, not a urea-bag. One root-nodule mention is enough.
A chemical fertiliser labelled bio because it “helps plants” is a miss.
Figure. Rhizobium fixes N2 inside the root. A mycorrhiza widens P uptake. The claim stays at that job — not 'bacteria make the plant grow'.
How it works
- Name the taught help-jobBiofertiliser.
- Keep Rhizobium if taughtThe case.
- Refuse a urea-swapA microbe-job.
7A miss: treating every microbe as a germ
A miss: treating every microbe as a germ. This chapter’s microbes have jobs. Germ is a pathogen-word; worker is this heading.
A scare as the whole welfare-chapter is the miss.
Figure. Treating every microbe as a germ collapses the chapter into a warning poster. The exam asks which job, in which place.
How it works
- Keep pathogen as a different chapter-wordGerm.
- Name the job hereWorker.
- Refuse every-microbe-as-germThe miss named.
8Keep the claim at the job the microbe does
Keep the claim at the job the microbe does: curd, antibiotic, clean, methane, check, help. A “microbes are useful” slogan is a mute bag.
A slogan with no named job is not a claim.
Figure. The kept claim is the chemical job: lactic acid in milk. 'Useful' is a compliment, not a Class 12 answer.
How it works
- Name the jobThe claim-size.
- Attach the microbe if taughtThe who.
- Refuse a nameless sloganThis class.
Rhizobium here is
- A biofertiliser-look as taught
- A pathogen always
- A fruit
A help-job.
Notes
- Mapped to the official NCERT chapter “Microbes in Human Welfare”. Original teaching only — no textbook sentences.
- Science here is Physics, Chemistry and Biology ideas at this class, never a language or social-science chapter.
Recap
Hold these pegs from the official chapter “Microbes in Human Welfare”. The wording is ExamMaster’s teaching, not a textbook recap.
- Microbes in Household Products
- Household products: curd, dough, a named ferment as taught — a microbe-job in the kitchen.
- Microbes in Industrial Products
- Industrial products: antibiotics, enzymes, a named drink-or-acid as taught.
- Microbes in Sewage Treatment
- Sewage treatment: microbes that clean a water-look as taught — BOD if named.
- Microbes in Production of Biogas
- Biogas: a methane-look from a taught mix of microbes.
- Microbes as Biocontrol Agents
- Biocontrol: a microbe (or its leftover) that checks a pest as taught.
- Microbes as Biofertilisers
- Biofertilisers: microbes that help a plant’s nutrient-look as taught — Rhizobium if named.
Practise Microbes in Human Welfare
Reading is free and needs no account. Practice, mocks and progress live in the app.
- A 4-question practice set that ends the chapter
- 1 quick check with worked explanations
- Timed mocks scored with the real marking scheme
- Readiness tracked per topic, kept on your device