Chapter 8 of Class 12 Biology, Microbes in Human Welfare, explains how microscopic organisms that we usually fear can actually help us. These microbes play a vital role in making curd, cleaning waste, making alcohol, controlling pests, and even in producing antibiotics. This chapter helps students understand the useful side of microbes, especially in agriculture, industry, and environment.
I chose to write about this chapter because students often ignore it thinking it’s just about examples. But NCERT includes many match-the-following type questions, MCQs, and application-based questions from this chapter. It’s also quite useful for NEET biology. The content is full of real-world applications like biofertilisers, sewage treatment, and genetically modified organisms. Once you relate it to your surroundings — like the curd in your fridge or the smell from compost — this chapter becomes very easy and interesting to revise. By reading and downloading the PDF from NCERT, students can strengthen their base and write better answers in exams.
Key Concepts of Microbes in Human Welfare – Class 12 Biology
This chapter is all about the beneficial uses of microorganisms. While microbes like bacteria, fungi, and protozoa can cause diseases, this chapter focuses on their positive uses.
Microbes in Household Products
Microbes are part of many things we consume or use daily.
- Lactobacillus is used to make curd from milk
- Yeast (Saccharomyces cerevisiae) is used in baking bread and making alcoholic beverages
- Traditional Indian foods like idli, dosa, and dhokla use fermentation by natural microbes
- Toddy, a fermented drink, is made by fermenting sap from palm plants
Microbes in Industrial Production
Microbes are used in producing:
| Product | Microorganism Used |
|---|---|
| Alcohol, Wine, Beer | Saccharomyces cerevisiae (yeast) |
| Antibiotics (e.g., Penicillin) | Penicillium notatum |
| Citric acid | Aspergillus niger |
| Acetic acid | Acetobacter aceti |
| Lactic acid | Lactobacillus |
Fermenters or bioreactors are used for large-scale production of these products in industries.
Microbes in Sewage Treatment
Microbes are used in treating wastewater to make it less harmful before releasing it into rivers.
- Primary treatment removes large solids
- Secondary treatment uses aerobic bacteria to remove organic matter
- The activated sludge formed contains bacteria that digest waste
- Biogas is also produced as a by-product, which can be used as fuel
Microbes in Biogas Production
Anaerobic bacteria called Methanogens are used in gobar gas plants
- These bacteria are found in the rumen of cattle
- They break down waste material to release methane, a flammable gas
- Biogas plants are widely used in rural India for fuel and manure
Microbes as Biocontrol Agents
Instead of chemical pesticides, some microbes can be used to control pests naturally
- Bacillus thuringiensis (Bt) produces a toxin that kills insect larvae
- Bt toxin genes are inserted into cotton plants to make Bt-cotton
- Fungi like Trichoderma are used to control plant pathogens
- Ladybirds and dragonflies also act as biocontrol agents in organic farming
Microbes as Biofertilisers
Microbes help in improving soil fertility without chemical fertilisers
- Rhizobium fixes nitrogen in legume root nodules
- Azotobacter and Azospirillum are free-living nitrogen-fixers
- Mycorrhiza is a fungus that helps plants absorb water and nutrients
- Blue green algae like Anabaena and Nostoc are used in paddy fields
These methods help in sustainable and eco-friendly farming.
Important Diagrams to Revise
- Diagram of biogas plant
- Bioreactor or fermenter structure
- Stages in sewage treatment
- Rhizobium-root nodule interaction
These visuals make the chapter easier to understand and are important for boards and NEET.
Download PDF – NCERT Class 12 Biology Chapter 8
To download the original NCERT PDF of Chapter 8, follow these simple steps:
