Microbes in Human Welfare
Class 12 · Biology
4 ideas in Class 12 Biology, explained in plain words, with games and quizzes to practise.
Microbes in Food and Industry
Part of: Helpful Microbes
Lactic bacteria curdle milk into vitamin-rich curd, yeast raises bread and brews drinks, bacteria hole Swiss cheese and fungi ripen Roquefort. Penicillin from mould earned the 1945 Nobel prize, while Aspergillus, Acetobacter, Clostridium and Lactobacillus make acids, and streptokinase, cyclosporin and statins heal.
Why it matters. Microbe-product matching is the core of this section.
Key words
- LAB
- : Milk-curding lactic acid bacteria.
- Fermentor
- : Large vessels growing microbes.
- Penicillin
- : First mould antibiotic.
- Streptokinase
- : Clot-clearing bacterial enzyme.
- Cyclosporin
- : Transplant-protecting fungal molecule.
- Statins
- : Cholesterol-lowering yeast molecules.
Try it in two minutes
- Pair four acids with four microbes.
- Order mould to medicine for penicillin.
- Split distilled from undistilled drinks.
Try at home. Explain why bottled juice looks clearer than home juice.
Clean Water and Fuel
Part of: Helpful Microbes
Primary treatment settles solids physically while secondary aeration lets flocs eat organics, cutting BOD before release. Sludge partly returns as inoculum and the rest digests into methane-rich biogas. Methanogens also fill cattle rumen, so dung feeds village plants whose tanks run 10 to 15 feet deep.
Why it matters. Stage order plus BOD assignment is the numerical core here.
Formulas
- Higher BOD means higher pollution
- Biogas holds methane, hydrogen sulphide, carbon dioxide
- Biogas tanks run 10 to 15 feet deep
Key words
- BOD
- : Oxygen needed to oxidise organics.
- Flocs
- : Meshes of bacteria and fungi.
- Activated sludge
- : Settled flocs partly recycled.
- Methanogens
- : Methane-making anaerobic bacteria.
- Biogas
- : Methane-rich fuel from digestion.
- Inoculum
- : Starter culture recycled to tanks.
Try it in two minutes
- Order settle, aerate, digest.
- Rank 400, 20 and 8 BOD samples.
- Trace dung to cooking flame.
Try at home. Explain why untreated sewage spreads water-borne disease.
Biocontrol Agents
Part of: Field Helpers
Ladybirds eat aphids and dragonflies eat mosquitoes, Bt toxin released in caterpillar guts destroys them while sparing others, Bt-cotton carries the toxin gene, Trichoderma guards roots, and baculoviruses strike narrow insect spectra without harming mammals or birds.
Why it matters. Specificity reasoning separates biocontrol from chemical sprays.
Key words
- Biocontrol
- : Pest control by living agents.
- Bt toxin
- : Caterpillar-gut poison from bacteria.
- Bt-cotton
- : Cotton carrying toxin genes.
- Trichoderma
- : Root fungus fighting pathogens.
- Baculovirus
- : Narrow insect-attacking virus.
Try it in two minutes
- Pair each agent with its target.
- Track toxin from sachet to gut.
- List spared non-targets.
Try at home. Explain why Bt-cotton needs fewer sprays.
Biofertilisers
Part of: Soil Feeders
Rhizobium fixes nitrogen in legume nodules while Azospirillum and Azotobacter live free in soil. Glomus mycorrhiza passes phosphorus to plants, and paddy cyanobacteria like Anabaena add nitrogen plus organic matter, cutting chemical fertiliser need.
Why it matters. Symbiotic versus free-living splits answer most questions here.
Key words
- Biofertiliser
- : Organisms enriching soil nutrients.
- Rhizobium
- : Nodule bacteria feeding legumes.
- Mycorrhiza
- : Fungus-root nutrient exchange.
- Glomus
- : Phosphorus-fetching fungal genus.
- Cyanobacteria
- : Nitrogen-fixing photosynthetic microbes.
Try it in two minutes
- Split fixers by address.
- Follow phosphorus into roots.
- Flood paddy with cyanobacteria.
Try at home. Explain what the fungus gains from mycorrhiza.
What your child will practise
- Biocontrol Agents: Desert Puzzle (Clue Puzzle)
- Biocontrol Agents: Desert Quick Fire (Quick Fire)
- Biofertilisers: Space Puzzle (Clue Puzzle)
- Clean Water and Fuel: Space Quest (Flip and Match)
- Microbes in Food and Industry: Jungle Quick Fire (Quick Fire)
- Quiz: Biocontrol Agents (8 questions)
- Quiz: Biofertilisers (8 questions)
- Quiz: Clean Water and Fuel (8 questions)
- Quiz: Microbes in Food and Industry (8 questions)