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Microbes in Human Welfare Solutions
Welcome to ExamSpark! Students will learn how microbes produce curd, antibiotics, biogas, biofertilizers, and treat sewage. This chapter is highly important for CBSE Board Exams 2026-27, carrying 4-6 marks, and is essential for NEET where 1-2 questions consistently appear. Note: According to CBSE Syllabus 2023-24, this chapter is renumbered as Chapter 8, but NCERT textbooks still label it as Chapter 10. Let's make Biology simple!
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Chapter NameMicrobes in Human Welfare
SubjectBiology
ClassClass 12
BoardCBSE / State Boards
Important TopicsBiogas, Sewage Treatment, Biofertilizers, Antibiotics
Difficulty LevelEasy-Medium
Exam Weightage4-6 marks (CBSE); 1-2 questions (NEET)
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Learning Objectives
- Explain microbial roles in household products like curd, cheese, and traditional Indian foods.
- Describe LAB (Lactic Acid Bacteria) and their nutritional benefits (Vitamin B12).
- Understand industrial microbial products: antibiotics, organic acids, enzymes, beverages.
- Differentiate between primary and secondary sewage treatment with processes.
- Explain BOD (Biochemical Oxygen Demand) and its relation to water pollution.
- Describe biogas production with methanogens and biogas plant structure.
- Identify biofertilizers (Rhizobium, Azotobacter, cyanobacteria) and their nitrogen-fixing role.
- Explain biocontrol agents and bioactive molecules.
Key Concepts, Definitions & Formulas
- Microbes: Microscopic organisms (bacteria, fungi, yeasts, protozoans, viruses) not visible to naked eye.
- LAB (Lactic Acid Bacteria): Bacteria like Lactobacillus that produce lactic acid, coagulate milk proteins, and increase Vitamin B12.
- Curd: Milk product formed when LAB produce acids that coagulate and digest milk proteins (casein).
- Fermentation: Metabolic process where microbes release gases (CO2, methane) during metabolism.
- Sewage: Municipal waste material carried in drains; rich in pathogenic microbes and organic matter.
- Primary Treatment: Mechanical/physical removal of suspended particles by sedimentation and filtration.
- Secondary Treatment: Biological treatment using aerobic/anaerobic microbes to digest organic matter.
- Flocs: Masses of bacteria associated with fungal filaments in activated sludge.
- BOD (Biochemical Oxygen Demand): Amount of oxygen needed to oxidize organic matter in 1 litre of water; higher BOD = more polluted.
- Biogas: Methane-rich gas produced by anaerobic degradation of biomass; contains CH4, CO2, H2S.
- Methanogens: Methane-producing bacteria (e.g., Methanobacterium) that produce biogas under anaerobic conditions.
- Biofertilizers: Living entities (bacteria, cyanobacteria, fungi) that increase soil fertility by fixing nitrogen.
- Biocontrol Agents: Microbes that control pest insects/plant pathogens without chemicals.
- Cyclosporin A: Immunosuppressive drug from Trichoderma polysporum; used in organ transplantation.
- Statins: Blood cholesterol-lowering agents from Monascus purpureus (yeast); competitively inhibit cholesterol synthesis.
- Streptokinase: Clot-buster enzyme from Streptococcus; dissolves blood clots in heart attack patients.
Key Formulas & Reactions
- Biogas Production Reactions: $CO_2 + 4H_2 \rightarrow CH_4 + 2H_2O$ and $CH_3OH \rightarrow CH_4 + O_2$.
- BOD Interpretation: BOD > 400 mg/L = Highly polluted (untreated sewage). BOD 20-30 mg/L = Moderately polluted. BOD < 10 mg/L = Clean water (river water).
Important Microorganisms
| Microbe | Product/Use | Application |
|---|---|---|
| Lactobacillus | Lactic acid | Curd formation, Vitamin B12 |
| Saccharomyces cerevisiae | Ethanol, CO2 | Bread, beer, wine |
| Propionibacterium shermanii | CO2 | Swiss cheese holes |
| Penicillium notatum | Penicillin | Antibiotic |
| Cephalosporium acremonium | Cephalosporin | Antibiotic |
| Methanobacterium | Methane | Biogas production |
| Rhizobium | Nitrogen fixation | Biofertilizer (legumes) |
| Azotobacter | Nitrogen fixation | Free-living biofertilizer |
| Bacillus thuringiensis | Cry toxin | Biopesticide |
| Trichoderma | Biocontrol | Plant pathogen control |
| Trichoderma polysporum | Cyclosporin A | Immunosuppressive |
| Monascus purpureus | Statins | Cholesterol lowering |
| Streptococcus | Streptokinase | Clot-buster |
Full NCERT Solutions (Step-by-Step)
Question 1: Bacteria cannot be seen with the naked eye, but these can be seen with the help of a microscope. If you have to carry a sample from your home to your biology laboratory to demonstrate the presence of microbes with the help of a microscope, which sample would you carry and why?
Answer:
Identify sample. Sample to carry: Curd.
Reason. Curd contains plenty of Lactobacillus (lactic acid bacteria). These bacteria produce acids that coagulate and digest milk proteins. A small drop of curd consists of millions of bacteria, which can be observed easily under a microscope.
Identify sample. Sample to carry: Curd.
Reason. Curd contains plenty of Lactobacillus (lactic acid bacteria). These bacteria produce acids that coagulate and digest milk proteins. A small drop of curd consists of millions of bacteria, which can be observed easily under a microscope.
Question 2: Give examples to prove that microbes release gases during metabolism.
Answer:
Methane production. Methanobacterium in anaerobic sludge releases large amounts of methane along with hydrogen gas and carbon dioxide.
Fermentation processes. Cheese fermentation releases CO2 (by Propionibacterium shermanii). Dough fermentation releases CO2 (by Saccharomyces cerevisiae). Beverage production releases CO2 (by lactic acid bacteria).
Methane production. Methanobacterium in anaerobic sludge releases large amounts of methane along with hydrogen gas and carbon dioxide.
Fermentation processes. Cheese fermentation releases CO2 (by Propionibacterium shermanii). Dough fermentation releases CO2 (by Saccharomyces cerevisiae). Beverage production releases CO2 (by lactic acid bacteria).
Question 3: In which food would you find lactic acid bacteria? Mention some of their useful applications.
Answer:
Food containing LAB. Curd.
Nutritional enhancement. Increases Vitamin B12 level in curd and enhances overall nutritional value.
Food fermentation. Used to ferment/culture food products.
Health benefits. Improve gut health and check growth of disease-causing microbes in the stomach.
Milk coagulation. Produce acids that coagulate and partially digest milk proteins (casein).
Food containing LAB. Curd.
Nutritional enhancement. Increases Vitamin B12 level in curd and enhances overall nutritional value.
Food fermentation. Used to ferment/culture food products.
Health benefits. Improve gut health and check growth of disease-causing microbes in the stomach.
Milk coagulation. Produce acids that coagulate and partially digest milk proteins (casein).
Question 4: Name some traditional Indian foods made of wheat, rice and Bengal gram (or their products) which involve use of microbes.
Answer:
Traditional Foods Table.
Microbial role. All these foods use fermentation by bacteria/yeasts that release CO2, making them soft and porous.
Traditional Foods Table.
| Base Material | Traditional Foods |
|---|---|
| Wheat | Bread, Bhatura, Cake |
| Rice | Idli, Dosa, Uttapam |
| Bengal Gram | Dhokla, Khandvi |
Question 5: In which way have microbes played a major role in controlling diseases caused by harmful bacteria?
Answer:
Antibiotic production. Microbes produce antibiotics to treat harmful diseases like leprosy, diphtheria.
Antitoxins/Antisera. Microbes produce antitoxins or antisera against specific pathogens, widely used against lock-jaw tetanus, diphtheria.
Antibody production. Produce antibodies containing antitoxins and opsonins, checking occurrence of diseases like cholera, typhoid, smallpox.
Cell wall destruction. Antibiotics destroy bacteria by weakening cell walls. Immune cells (white blood cells) enter bacterial cell causing cell lysis.
Penicillin example. Penicillium notatum (fungus) produces penicillin, which inhibits growth of Staphylococci bacteria in the body.
Antibiotic production. Microbes produce antibiotics to treat harmful diseases like leprosy, diphtheria.
Antitoxins/Antisera. Microbes produce antitoxins or antisera against specific pathogens, widely used against lock-jaw tetanus, diphtheria.
Antibody production. Produce antibodies containing antitoxins and opsonins, checking occurrence of diseases like cholera, typhoid, smallpox.
Cell wall destruction. Antibiotics destroy bacteria by weakening cell walls. Immune cells (white blood cells) enter bacterial cell causing cell lysis.
Penicillin example. Penicillium notatum (fungus) produces penicillin, which inhibits growth of Staphylococci bacteria in the body.
Question 6: Name any two species of fungus, which are used in the production of the antibiotics.
Answer:
Penicillin. Fungal source: Penicillium notatum.
Cephalosporin. Fungal source: Cephalosporium acremonium.
Penicillin. Fungal source: Penicillium notatum.
Cephalosporin. Fungal source: Cephalosporium acremonium.
Question 7: What is sewage? In which way can sewage be harmful to us?
Answer:
Definition of Sewage. Municipal waste material carried away in drains and sewers. Includes both solid and liquid wastes rich in microbes and organic matter.
Harmful effects. Most microbes in sewage are pathogenic and cause water-borne diseases. Sewage water is a major cause of contaminating drinking water, leading to outbreaks of diseases like cholera and typhoid. It also pollutes rivers, lakes, and soil, and reduces oxygen levels in water bodies.
Definition of Sewage. Municipal waste material carried away in drains and sewers. Includes both solid and liquid wastes rich in microbes and organic matter.
Harmful effects. Most microbes in sewage are pathogenic and cause water-borne diseases. Sewage water is a major cause of contaminating drinking water, leading to outbreaks of diseases like cholera and typhoid. It also pollutes rivers, lakes, and soil, and reduces oxygen levels in water bodies.
Question 8: What is the key difference between primary and secondary sewage treatment?
Answer:
Primary vs Secondary Table.
Key Point: Primary = physical; Secondary = biological (microbial).
Primary vs Secondary Table.
| Primary Sewage Treatment | Secondary Sewage Treatment |
|---|---|
| Mechanical/physical removal of small and large substances | Biological removal of organic matter by microbes |
| Process: Sedimentation and filtration | Process: Biological digestion of wastes |
| Less complicated, relatively low-priced | Complicated process, expensive |
| Removes suspended particles | Removes organic matter (reduces BOD) |
| Also called physical treatment | Also called biological treatment |
Key Point: Primary = physical; Secondary = biological (microbial).
Question 9: Do you think microbes can also be used as source of energy? If yes, how?
Answer:
Biogas production. Bacteria like Methane bacterium (Methanobacterium) generate biogas (gobar gas).
Biogas plant structure. Concrete tank (10-15 feet depth) with outlets and inlets. Slurry (dung mixed with water) is poured into the tank. Digester is filled with anaerobic methane-producing bacteria.
Process. Under anaerobic conditions, bacteria produce biogas from slurry, which is extracted through a pipe for use as energy.
Composition. Mainly methane (CH4), along with CO2, H2S, and traces of H2.
Byproduct. Slurry removed from the outlet is used as fertilizer.
Biogas production. Bacteria like Methane bacterium (Methanobacterium) generate biogas (gobar gas).
Biogas plant structure. Concrete tank (10-15 feet depth) with outlets and inlets. Slurry (dung mixed with water) is poured into the tank. Digester is filled with anaerobic methane-producing bacteria.
Process. Under anaerobic conditions, bacteria produce biogas from slurry, which is extracted through a pipe for use as energy.
Composition. Mainly methane (CH4), along with CO2, H2S, and traces of H2.
Byproduct. Slurry removed from the outlet is used as fertilizer.
Question 10: Microbes can be used to decrease the use of chemical fertilisers and pesticides. Explain how this can be accomplished.
Answer:
Biofertilizers. Biofertilizers are living entities that increase soil fertility. They are introduced into roots, seeds, and soil to make nutrients available. Symbiotic: Rhizobium in root nodules of leguminous plants. Free-living bacteria: Azotobacter, Azospirillum. Cyanobacteria: Nostoc, Oscillatoria, Anabaena.
Biopesticides. Bacillus thuringiensis produces a toxin that kills insect pests. Trichoderma are free-living fungi in roots that safeguard plants from pathogens. Baculovirus acts as a biological control agent against arthropods and insects (effective against cotton bollworm).
Biofertilizers. Biofertilizers are living entities that increase soil fertility. They are introduced into roots, seeds, and soil to make nutrients available. Symbiotic: Rhizobium in root nodules of leguminous plants. Free-living bacteria: Azotobacter, Azospirillum. Cyanobacteria: Nostoc, Oscillatoria, Anabaena.
Biopesticides. Bacillus thuringiensis produces a toxin that kills insect pests. Trichoderma are free-living fungi in roots that safeguard plants from pathogens. Baculovirus acts as a biological control agent against arthropods and insects (effective against cotton bollworm).
Question 11: Three water samples namely river water, untreated sewage water and secondary effluent discharged from a sewage treatment plant were subjected to BOD test. The samples were labelled A, B and C; but the laboratory attendant did not note which was which. The BOD values of the three samples A, B and C were recorded as 20mg/L, 8 mg/L and 400mg/L, respectively. Which sample of the water is most polluted? Can you assign the correct label to each assuming the river water is relatively clean?
Answer:
Define BOD. Biochemical Oxygen Demand (BOD) is the amount of oxygen consumed if all organic matter in 1 litre of water is oxidized by bacteria. Higher BOD = Greater polluting potential.
Assign samples.
Most Polluted: Sample C (highest BOD = 400 mg/L).
Define BOD. Biochemical Oxygen Demand (BOD) is the amount of oxygen consumed if all organic matter in 1 litre of water is oxidized by bacteria. Higher BOD = Greater polluting potential.
Assign samples.
| Sample | BOD Value | Water Type | Pollution Level |
|---|---|---|---|
| A | 20 mg/L | Secondary effluent | Moderately polluted |
| B | 8 mg/L | River water | Relatively clean |
| C | 400 mg/L | Untreated sewage | Most polluted |
Question 12: Find out the name of the microbes from which Cyclosporin A (an immunosuppressive drug) and Statins (blood cholesterol lowering agents) are obtained.
Answer:
Bioactive Molecules Table.
Mechanisms. Statins competitively inhibit the enzyme responsible for cholesterol synthesis. Cyclosporin A prevents the body from rejecting a new organ during transplantation.
Bioactive Molecules Table.
| Bioactive Molecule | Microbial Source | Type | Medical Use |
|---|---|---|---|
| Cyclosporin A | Trichoderma polysporum | Fungus | Immunosuppressive drug for organ transplantation |
| Statins | Monascus purpureus | Yeast | Blood cholesterol lowering agent |
Question 13: Find out the role of microbes in the following and discuss it with your teacher. (a) Single cell protein (SCP) (b) Soil
Answer:
Single Cell Protein (SCP). SCP involves harmless microbial cells consumed as protein-enriched food. They are rich in minerals, proteins, fats, vitamins, and carbohydrates. Examples include mushrooms and yeast. Large-scale cultivation of Methylophilus methylotrophus and Spirulina can be done on starch-like wastewater, molasses, straw, and sewage.
Soil. Microbes are crucial for maintaining soil fertility and help form nutrient-rich humus by decomposition. Nitrogen fixation is carried out by symbiotic microbes (Rhizobium) and free-living bacteria (Azotobacter, Azospirillum, Cyanobacteria) to fix atmospheric nitrogen into a plant-usable form.
Single Cell Protein (SCP). SCP involves harmless microbial cells consumed as protein-enriched food. They are rich in minerals, proteins, fats, vitamins, and carbohydrates. Examples include mushrooms and yeast. Large-scale cultivation of Methylophilus methylotrophus and Spirulina can be done on starch-like wastewater, molasses, straw, and sewage.
Soil. Microbes are crucial for maintaining soil fertility and help form nutrient-rich humus by decomposition. Nitrogen fixation is carried out by symbiotic microbes (Rhizobium) and free-living bacteria (Azotobacter, Azospirillum, Cyanobacteria) to fix atmospheric nitrogen into a plant-usable form.
Question 14: Arrange the following in the decreasing order (most important first) of their importance, for the welfare of human society. Give reasons for your answer. Biogas, Citric acid, Penicillin and Curd.
Answer:
Decreasing Order. Penicillin > Biogas > Curd > Citric acid.
Reasons.
Decreasing Order. Penicillin > Biogas > Curd > Citric acid.
Reasons.
| Rank | Product | Reason |
|---|---|---|
| 1 | Penicillin | Antibiotic that kills pathogens causing harmful diseases/infections -> saves lives (most important) |
| 2 | Biogas | Non-polluting clean fuel from sewage byproduct; used for cooking and lighting in remote areas |
| 3 | Curd | High nutritional value (Vitamin B12); maintains gut health; replaces harmful bacteria |
| 4 | Citric acid | Used as food preservative (least critical for welfare) |
Question 15: How do biofertilisers enrich the fertility of the soil?
Answer:
Definition. Biofertilizers are living entities (bacteria, cyanobacteria, fungi) that increase soil fertility. They act as natural fertilizers instead of chemical ones.
Need. To reduce dependence on harmful chemical fertilizers and promote organic farming.
Types. Symbiotic: Rhizobium in root nodules of leguminous plants. Free-living bacteria: Azotobacter, Azospirillum. Cyanobacteria: Nostoc, Oscillatoria, Anabaena.
Definition. Biofertilizers are living entities (bacteria, cyanobacteria, fungi) that increase soil fertility. They act as natural fertilizers instead of chemical ones.
Need. To reduce dependence on harmful chemical fertilizers and promote organic farming.
Types. Symbiotic: Rhizobium in root nodules of leguminous plants. Free-living bacteria: Azotobacter, Azospirillum. Cyanobacteria: Nostoc, Oscillatoria, Anabaena.
EXTRA IMPORTANT QUESTIONS (BOARD EXAM 2026 STYLE)
ExamSpark par humari koshish rehti hai ki aapko complete practice mile. Here are highly expected questions in the 2026 Board Exams!
Multiple Choice Questions (MCQs)
Q1. Which microbe is used in biogas production?
(a) Rhizobium
(b) Methanogens
(c) Azotobacter
(d) Trichoderma
Answer:
Identify. (b) Methanogens. Methanobacterium produces methane under anaerobic conditions.
Identify. (b) Methanogens. Methanobacterium produces methane under anaerobic conditions.
Q2. Which bacteria fixes nitrogen in leguminous plants?
(a) Azotobacter
(b) Rhizobium
(c) Nostoc
(d) Oscillatoria
Answer:
Identify. (b) Rhizobium. Forms symbiotic relationship in root nodules of legumes.
Identify. (b) Rhizobium. Forms symbiotic relationship in root nodules of legumes.
Q3. Which microbe produces Cyclosporin A?
(a) Monascus purpureus
(b) Trichoderma polysporum
(c) Streptococcus
(d) Penicillium
Answer:
Identify. (b) Trichoderma polysporum. It is a fungus producing immunosuppressive drug.
Identify. (b) Trichoderma polysporum. It is a fungus producing immunosuppressive drug.
Q4. Which enzyme is used as clot-busting?
(a) Pectinase
(b) Streptokinase
(c) Lipase
(d) Amylase
Answer:
Identify. (b) Streptokinase. Derived from Streptococcus, it dissolves blood clots.
Identify. (b) Streptokinase. Derived from Streptococcus, it dissolves blood clots.
Q5. LAB increases which vitamin in curd?
(a) Vitamin A
(b) Vitamin B12
(c) Vitamin C
(d) Vitamin D
Answer:
Identify. (b) Vitamin B12.
Identify. (b) Vitamin B12.
Q6. BOD test is performed at which stage of sewage treatment?
(a) Primary treatment
(b) Secondary treatment
(c) Tertiary treatment
(d) Before treatment
Answer:
Identify. (b) Secondary treatment.
Identify. (b) Secondary treatment.
Short Answer Questions (2-3 Marks)
Q7. Why is secondary treatment of sewage called biological treatment?
Answer:
Explanation. Organic wastes are digested by aerobic/anaerobic microbes, therefore it relies entirely on biological processes.
Explanation. Organic wastes are digested by aerobic/anaerobic microbes, therefore it relies entirely on biological processes.
Q8. What is the medical use of Cyclosporin A?
Answer:
Medical Use. Used as an immunosuppressive drug during organ transplantation to prevent rejection.
Medical Use. Used as an immunosuppressive drug during organ transplantation to prevent rejection.
Q9. Name pests that ladybirds and dragonflies help get rid of.
Answer:
Identification. Ladybirds help control Aphids. Dragonflies help control Mosquitoes.
Identification. Ladybirds help control Aphids. Dragonflies help control Mosquitoes.
Q10. Why are commercially bottled fruit juices clearer than homemade juices?
Answer:
Reasoning. Bottled juices are treated with pectinase and protease enzymes that digest pectin and proteins causing cloudiness; homemade juices lack these enzymes.
Reasoning. Bottled juices are treated with pectinase and protease enzymes that digest pectin and proteins causing cloudiness; homemade juices lack these enzymes.
Long Answer Questions (5 Marks)
Q11. Describe the process involved in sewage treatment with flowchart.
Answer:
Primary Treatment. Physical removal of suspended materials in settling tanks, reducing BOD.
Secondary Treatment. Aeration tank with heterotrophic microbes consume organic matter. Flocs form (bacterial masses with fungal filaments). Settling tank forms activated sludge. A part returns to the aeration tank; the rest to anaerobic sludge digesters.
Primary Treatment. Physical removal of suspended materials in settling tanks, reducing BOD.
Secondary Treatment. Aeration tank with heterotrophic microbes consume organic matter. Flocs form (bacterial masses with fungal filaments). Settling tank forms activated sludge. A part returns to the aeration tank; the rest to anaerobic sludge digesters.
Case-Based Questions
Q12. Case Study: A farmer wants to improve nitrogen content in soil for non-leguminous crop. River water (BOD = 8 mg/L), secondary effluent (BOD = 20 mg/L), and untreated sewage (BOD = 400 mg/L) are available.
(a) Recommend two microbes to enrich soil with nitrogen.
(b) Why do leguminous crops not require such enrichment?
(c) Which water sample is safest for irrigation?
Answer:
(a) Azotobacter and Azospirillum (free-living nitrogen-fixing bacteria).
(b) Legumes have root nodules with Rhizobium (symbiotic nitrogen-fixing bacteria) that fix atmospheric nitrogen naturally.
(c) River water (BOD = 8 mg/L), as lowest BOD means least polluted.
(a) Azotobacter and Azospirillum (free-living nitrogen-fixing bacteria).
(b) Legumes have root nodules with Rhizobium (symbiotic nitrogen-fixing bacteria) that fix atmospheric nitrogen naturally.
(c) River water (BOD = 8 mg/L), as lowest BOD means least polluted.
Assertion-Reason Questions
Directions: (A) Both true, Reason explains Assertion. (B) Both true, Reason doesn't explain. (C) Assertion true, Reason false. (D) Both false.
Q13. Assertion: Statins are products of fermentation activity of Monascus purpureus. Reason: Statins commercially used as blood cholesterol lowering agent.
Answer:
Verification. (B) Both true, Reason doesn't explain Assertion.
Verification. (B) Both true, Reason doesn't explain Assertion.
Q14. Assertion: Bacillus thuringiensis possesses insecticidal Cry protein and thus kills larvae of certain insects. Reason: There are transgenic crop plants that develop natural resistance to insects by inserting cry genes of Bacillus thuringiensis into them.
Answer:
Verification. (B) Both true, Reason doesn't explain.
Verification. (B) Both true, Reason doesn't explain.
Q15. Assertion: BOD is a measure of inorganic matter present in wastewater. Reason: The greater the BOD of wastewater, more is its polluting potential.
Answer:
Verification. (D) Both false (Note: Assertion is false as BOD measures organic matter, but the answer key marks D).
Verification. (D) Both false (Note: Assertion is false as BOD measures organic matter, but the answer key marks D).
COMMON MISTAKES STUDENTS MAKE
- Confusing Cyclosporin A source: From Trichoderma polysporum (fungus), not yeast. Fungus = Cyclosporin; Yeast = Statins.
- Writing Rhizobium for non-legumes: Rhizobium = legumes only; Use Azotobacter/Azospirillum for non-legumes.
- Missing Vitamin B12 in LAB benefits: LAB increases B12 in curd. Always mention B12 for LAB.
- Not specifying anaerobic for biogas: Biogas requires anaerobic conditions for methane production.
- Confusing Concepts: Biofertilizers vs Biopesticides (increase nutrients vs kill pests), Distilled vs Non-distilled beverages, Symbiotic vs Free-living nitrogen fixers, Flocs vs Activated Sludge.
EXAM PREPARATION TIPS
- Always italicize microorganism names: Lactobacillus, Penicillium. It carries marks!.
- Master the high-yield topics: Sewage treatment (primary vs secondary), Biogas production with diagram, Biofertilizers (Rhizobium, cyanobacteria), and Biocontrol agents (Bt, Trichoderma).
- Answer Formatting: Direct answers for 1-mark questions. For 5-mark questions, use intro, main explanation with subheadings, essential diagrams (biogas/sewage), and a conclusion (150-200 words).
- Time Management: Allocate 10 minutes for Section A, 35 minutes for Section B, 45 minutes for Section C, 25 minutes for Section D, and 50 minutes for Section E. Start with diagrams first — they're quick and guarantee marks!.
FAQ SECTION
1. Is Chapter 10 (Microbes in Human Welfare) important for CBSE Board 2026?
Yes, it's a moderately important chapter, carrying 4-6 marks in Section A & B. Questions are frequently asked from sewage treatment, biogas, and biofertilizers.
2. Where can I download NCERT PDF for this chapter?
Download from ncert.nic.in (official NCERT website) or use apps like PW Live, BYJU'S, Vedantu for free PDF downloads.
3. Which questions from NCERT exercises are most important for boards?
Most important: Q2 (gases during metabolism), Q8 (primary vs secondary treatment), Q9 (biogas), Q10 (biofertilizers & biopesticides), Q11 (BOD), Q12 (bioactive molecules).
4. Is this chapter important for NEET 2026?
Yes! Usually 1-2 questions come from this chapter in NEET consistently. High-yield topics: Methanogens, Rhizobium, Trichoderma, Cyclosporin A, Streptokinase.
5. What is the difference between Chapter 8 and Chapter 10?
CBSE Syllabus 2023-24 renumbered it as Chapter 8, but NCERT textbooks still show Chapter 10. Both refer to the same chapter.
CONCLUSION
Stay focused and confidently prepare for your 2026 Board Exams. You've got this!
More Class 12 Biology Chapters
Ch 1: Reproduction in Organisms
Ch 2: Sexual Reproduction
Ch 3: Human Reproduction
Ch 4: Reproductive Health
Ch 5: Principles of Inheritance
Ch 6: Molecular Basis
Ch 7: Evolution
Ch 8: Human Health and Disease
Ch 9: Strategies for Enhancement
Ch 10: Microbes in Human Welfare
Ch 11: Biotech Principles
Ch 12: Biotech Applications
Ch 13: Organisms and Populations
Ch 14: Ecosystem
Ch 15: Biodiversity
Ch 16: Environmental Issues