Master Microbes in Human Welfare with CBSE Class 12 Biology Key Concepts & Revision Guide
FAQs on Ace Class 12 Biology: Microbes in Human Welfare NCERT Book PDF Free (2025-26)
1. What is the expected marks weightage for Chapter 10, Microbes in Human Welfare, in the CBSE Class 12 Biology board exam for 2025-26?
For the CBSE Class 12 Biology board exam 2025-26, the chapter 'Microbes in Human Welfare' is part of the unit 'Biology and Human Welfare'. This unit typically carries a weightage of around 12-14 marks. You can expect questions worth a total of 3 to 5 marks from this specific chapter, often comprising a mix of MCQs, 2-mark, and occasionally a 3-mark or a component of a 5-mark question.
2. Which topics from 'Microbes in Human Welfare' are most important for 3 and 5-mark questions in the board exams?
For higher-mark questions (3 and 5 marks), you should focus on processes that can be explained in steps or have multiple components. The most important topics are:
Sewage Treatment: The entire process involving primary and secondary treatment, including the role of flocs, Biochemical Oxygen Demand (BOD), and the activated sludge process.
Biogas Production: The structure of a biogas plant and the roles of different groups of bacteria (methanogens) in the anaerobic digestion of sludge.
Industrial Production of Bioactive Molecules: Questions on specific microbes, the bioactive molecules they produce, and their medical applications (e.g., Cyclosporin A, Statins).
3. Name some important bioactive molecules of microbial origin and their uses that are frequently asked in exams.
Certain bioactive molecules are very important for exams. Students must remember the microbe, the chemical, and its function:
Statins: Produced by the yeast Monascus purpureus. They act as blood-cholesterol lowering agents by competitively inhibiting the enzyme responsible for cholesterol synthesis.
Cyclosporin A: Produced by the fungus Trichoderma polysporum. It is used as an immunosuppressive agent in organ-transplant patients.
Streptokinase: Produced by the bacterium Streptococcus. It is used as a 'clot buster' for removing clots from the blood vessels of patients who have suffered a myocardial infarction.
4. Why is the secondary treatment of sewage also called 'biological treatment'? What would be the consequence of skipping this step?
Secondary sewage treatment is called 'biological treatment' because it centrally involves the use of living microorganisms to break down the organic matter present in the effluent. The primary effluent is pumped into large aeration tanks where heterotrophic microbes grow into flocs (masses of bacteria associated with fungal filaments). These microbes consume the major part of the organic matter, significantly reducing the Biochemical Oxygen Demand (BOD). If this crucial step were skipped, the discharged water would have a very high BOD, meaning it is rich in organic pollutants. This would cause severe pollution in receiving water bodies, leading to the death of aquatic life due to oxygen depletion.
5. Students often confuse biofertilisers with chemical fertilisers. What is the fundamental advantage of using microbes as biofertilisers?
The fundamental advantage of using biofertilisers over chemical fertilisers is that they promote sustainable and eco-friendly agriculture by enriching the nutrient quality of the soil naturally. While chemical fertilisers provide a direct but often polluting source of nutrients, biofertilisers work in harmony with the ecosystem. For instance:
Bacteria like Rhizobium and Azotobacter fix atmospheric nitrogen, and fungi like Mycorrhiza help in phosphorus absorption.
They improve long-term soil fertility and texture without causing water pollution (eutrophication), which is a major drawback of chemical fertilisers.
6. Why are microbes like Baculoviruses considered excellent candidates for integrated pest management (IPM) programs?
Baculoviruses, particularly those under the genus Nucleopolyhedrovirus, are considered excellent for IPM programs due to their high degree of specificity. This is a key advantage for board exam answers. They are species-specific and have a narrow-spectrum insecticidal application. This means they are harmful to specific target insects (like beetles and caterpillars) but have no negative impact on non-target organisms such as plants, mammals, birds, fish, or even beneficial insects like honeybees. This makes them ideal for use in ecologically sensitive areas and as part of an IPM strategy to reduce reliance on broad-spectrum chemical pesticides.
