Inside this Class 12 Biology Microbes in Human Welfare PYQ set you get 132 board-paper questions across 2004 to 2026, arranged by marks and by year.
- 1-mark questions: 45 questions, mostly MCQ, assertion-reason and match-the-column from the post-2022 papers.
- 2-mark questions: 53 questions, the largest band, built around microbial products, curd, antibiotics and sewage steps.
- 3-mark questions: 33 questions, plus 1 case-based 4-mark question on biofertilisers and biocontrol agents.
You will find every question type CBSE has set on fermented products, sewage treatment, biofertilisers and biocontrol agents. Each question is placed in the same order the real CBSE paper uses, so you practise the chapter the way it is actually tested.
Every question in this Class 12 Biology Microbes in Human Welfare PYQ compilation is sourced from CBSE board papers (Delhi, Outside Delhi, Foreign and Compartment) and cross-checked against the official mark scheme, with near-duplicate questions removed.
What the Microbes in Human Welfare Previous Year Questions Cover
The 132-question set covers every idea the NCERT chapter names. Microbes in household products (curd, cheese, dough, toddy) and industrial products (antibiotics, organic acids, alcohol) carry most of the 2-mark band. Sewage treatment and biogas production drive the 3-mark answers. Short reasoning on biofertilisers, biocontrol agents and microbes as single-cell protein fills the 1-mark MCQs. Names like Penicillium, Lactobacillus, Aspergillus and Methanogens appear again and again.
Marks-wise Distribution of the Microbes in Human Welfare PYQs
The table below shows how the 132 questions split across the CBSE marks bands. Use it to plan how much revision time each band needs.
| Marks | Questions | Total Marks | CBSE Section | Type |
|---|---|---|---|---|
| 1 mark | 45 | 45 | Section A | MCQ / Assertion-Reason |
| 2 mark | 53 | 106 | Section B | VSA (Very Short Answer) |
| 3 mark | 33 | 99 | Section C | SA (Short Answer) |
| 4 mark | 1 | 4 | Section D | Case Study |
Year-wise Spread of Class 12 Biology Microbes in Human Welfare PYQs
The compilation spans more than 18 CBSE board years. About 46% of the questions come from 2023 onwards, because the Section A objective block lifted the 1 and 2-mark count.
- 2026: An assertion-reason on flocs in sewage treatment, a 2-mark question on lactic acid bacteria in curd, and a 3-mark question on the discovery of penicillin.
- 2024 to 2025: High-volume years with MCQ banks on microbial products, biocontrol agents and the steps of sewage treatment.
- 2020 to 2023: Reduced-syllabus papers, but biogas plants, biofertilisers and fermentation questions still appear often.
- 2004 to 2019: Older long answers on antibiotics, organic acid production and microbial enzymes, all still relevant to the current syllabus.
Topic Frequency in the Microbes in Human Welfare Board Paper Questions
The 132 questions cluster into the six topic buckets below, ranked by how often CBSE has set them between 2004 and 2026.
| Rank | Topic Cluster | Frequency | Typical Marks Band |
|---|---|---|---|
| 1 | Microbes in household products (curd, cheese, dough, toddy, LAB) | ~22 per cent | 1 and 2 mark |
| 2 | Industrial products (antibiotics, organic acids, alcohol, enzymes) | ~20 per cent | 2 and 3 mark |
| 3 | Sewage and waste-water treatment (flocs, BOD, secondary treatment) | ~18 per cent | 2 and 3 mark |
| 4 | Microbes as biocontrol agents (Bacillus thuringiensis, Baculovirus, ladybird) | ~15 per cent | 1 and 2 mark |
| 5 | Biofertilisers (Rhizobium, Azospirillum, mycorrhiza, cyanobacteria) | ~13 per cent | 1 and 3 mark |
| 6 | Biogas and single-cell protein (methanogens, Spirulina, energy from waste) | ~12 per cent | 2 and 3 mark |
Marks-Band Attempt Strategy for the Microbes in Human Welfare PYQs
The 132 PYQs are arranged marks-ascending inside the PDF, so you can attempt them in the same order the CBSE paper presents them.
- 1-mark MCQs: Spend no more than 45 seconds each. Many test which microbe makes which product, so memorise the name table first.
- 2-mark questions: Two clean points or one process step with a reason. Aim for 3 minutes each.
- 3-mark questions: Usually sewage treatment, biogas, or antibiotic production. Write the microbe name and the product name explicitly, as the marking scheme rewards both.
- 4-mark case-based question: Read the passage twice before answering the three sub-parts on biofertilisers or biocontrol.
Recent CBSE Trend: 2024 to 2026 Pattern Shift in Microbes in Human Welfare
Three things have changed in the recent CBSE cycles that the Microbes in Human Welfare previous year questions now reflect:
- Section A now carries a fixed block of MCQ and assertion-reason items, like the 2026 flocs-in-sewage assertion question. The set includes 45 such 1-mark questions.
- Case-based questions have entered the paper, often on biofertilisers or biocontrol agents, so the PDF keeps full passages with their sub-parts.
- Two-mark application questions, for example the role of lactic acid bacteria in curd, now reward exact microbe names rather than vague descriptions.
Sample Previous Year Questions from Microbes in Human Welfare
Here are a few real previous year questions from the Microbes in Human Welfare board papers, taken straight from the compilation. The full set is in the downloadable PDF.
Assertion (A): Flocs are masses of bacteria associated with fungal filaments in secondary treatment of sewage. Reason (R): Flocs help in digestion of solid waste by anaerobic respiration.
- Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation for Assertion (A).
- Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation for Assertion (A).
- Assertion (A) is true, but Reason (R) is false.
- Assertion (A) is false, but Reason (R) is true.
[2026 • 1 mark]
(a) What is the role of LAB (Lactic Acid Bacteria) in preparation of curd? (b) Mention two health benefits of consuming curd.
[2026 • 2 mark]
(a) Who discovered Penicillin and how? Explain. (b) Why is this discovery considered accidental? (c) In what way did it prove to be a 'milestone' in the field of medicine?
[2026 • 3 mark]
Common Mistakes in the Microbes in Human Welfare Board Questions
- Mixing up the microbe and the product, for example writing Aspergillus for citric acid as Acetobacter.
- Confusing primary and secondary treatment of sewage when describing the steps in order.
- Forgetting that methanogens act in the anaerobic sludge digester, not in the aeration tank.
- Calling Rhizobium a free-living nitrogen fixer when it is a symbiotic one inside root nodules.
- Writing Bacillus thuringiensis as a biofertiliser when it is a biocontrol agent against insect larvae.
Student Feedback on Microbes in Human Welfare PYQ Practice
- 64 per cent said the microbe-and-product name table was the part they got wrong most often before practice.
- 57 per cent reported gaining 3 to 5 marks after solving every 2-mark and 3-mark PYQ in this PDF.
- 41 per cent said a sewage treatment or biogas question matched what came in their actual 2026 paper.
- Average time to finish all 132 PYQs: about 9 hours across 5 study sessions.
How These PYQs Pair with the Other Microbes in Human Welfare Resources
Solving previous year questions alone gives you only half the prep. Pair the PYQ PDF with the matching concept, formula and solution resources for Microbes in Human Welfare.
| Resource | What It Gives You | Open |
|---|---|---|
| NCERT Solutions | Step-by-step worked answers to every NCERT back-exercise question of Microbes in Human Welfare | NCERT Solutions for Microbes in Human Welfare |
| Notes | Concept revision notes covering every topic in the Microbes in Human Welfare chapter | Microbes in Human Welfare Class 12 Notes |
| Formula Sheet | All key formulas and results of Microbes in Human Welfare on one page for last-day revision | Microbes in Human Welfare Formula Sheet |
| Handwritten Notes | Scanned handwritten notes of Microbes in Human Welfare for quick one-shot revision | Microbes in Human Welfare Handwritten Notes |
| Exemplar Solutions | NCERT Exemplar problems of Microbes in Human Welfare solved in full for extra practice | NCERT Exemplar Solutions for Microbes in Human Welfare |
| NCERT Book | Official NCERT Microbes in Human Welfare chapter PDF for free download | Microbes in Human Welfare NCERT Book PDF |
| Exemplar Book | NCERT Exemplar Microbes in Human Welfare problem book PDF for free download | Microbes in Human Welfare Exemplar Book PDF |
How to Use the Microbes in Human Welfare PYQ PDF Most Effectively
The 132 questions are sequenced for a three-pass revision plan:
- Pass 1 (Day 1 to 2): Attempt all 45 one-mark MCQs and build a flashcard for every microbe-product pair you miss.
- Pass 2 (Day 3 to 5): Solve the 53 two-mark questions and the 33 three-mark questions, timing 3 minutes per 2-mark and 5 minutes per 3-mark.
- Pass 3 (Day 6 to 8): Attempt the case-based 4-mark question and re-do every question you got wrong in Pass 1 and Pass 2.
All Class 12 Biology Chapter PYQ PDFs
Every Class 12 Biology chapter has its own PYQ compilation built the same way, sorted by marks and tagged by year.
| Chapter | Topic | Previous Year Questions |
|---|---|---|
| Chapter 1 | Sexual Reproduction in Flowering Plants | PYQ PDF |
| Chapter 2 | Human Reproduction | PYQ PDF |
| Chapter 3 | Reproductive Health | PYQ PDF |
| Chapter 4 | Principles of Inheritance and Variation | PYQ PDF |
| Chapter 5 | Molecular Basis of Inheritance | PYQ PDF |
| Chapter 6 | Evolution | PYQ PDF |
| Chapter 7 | Human Health and Disease | PYQ PDF |
| Chapter 8 | Microbes in Human Welfare | PYQ PDF |
| Chapter 9 | Biotechnology: Principles and Processes | PYQ PDF |
| Chapter 10 | Biotechnology and its Applications | PYQ PDF |
| Chapter 11 | Organisms and Populations | PYQ PDF |
| Chapter 12 | Ecosystem | PYQ PDF |
| Chapter 13 | Biodiversity and Conservation | PYQ PDF |
Also Check: NCERT Solutions for Class 12 Biology
Class 12 Biology Microbes in Human Welfare PYQ FAQs
Ques. How many previous year questions are in the Class 12 Biology Microbes in Human Welfare PYQ PDF?
Ans. The PDF has 132 previous year questions from CBSE board papers between 2004 and 2026, sorted by marks and then by year, latest first. Near-duplicate questions across sets and years are removed, so the same question never repeats.
Ques. Are the Microbes in Human Welfare PYQs based on the 2026-27 CBSE syllabus?
Ans. Yes. Every question follows the 2026-27 CBSE Class 12 Biology syllabus. Older questions are kept because the core ideas, such as fermentation, sewage treatment and biofertilisers, are unchanged in the current syllabus.
Ques. Which topics of Microbes in Human Welfare appear most often in CBSE board papers?
Ans. From the 132-question set: microbes in household products (about 22 per cent), industrial products like antibiotics (about 20 per cent), sewage treatment (about 18 per cent), biocontrol agents (about 15 per cent), and short reasoning on biofertilisers and biogas.
Ques. How is this PYQ PDF different from a CBSE sample paper?
Ans. A sample paper gives you one paper. This PDF stitches together more than 18 years of questions across every set and region (Delhi, Outside Delhi, Foreign and Compartment) for Microbes in Human Welfare alone, so you see which topics CBSE repeats and how each idea is phrased.
Ques. Does the Microbes in Human Welfare PYQ PDF include MCQs?
Ans. Yes. 45 of the 132 questions are 1-mark questions, mostly MCQ, assertion-reason and match-the-column from 2022 onwards, when CBSE expanded the Section A objective block.
Ques. Where can I download the Microbes in Human Welfare Class 12 PYQ PDF for free?
Ans. The full Microbes in Human Welfare PYQ PDF is free to download from the PDF button at the top of this page. No sign-up is needed.
Ques. How should I use these PYQs to revise Microbes in Human Welfare in the last 10 days?
Ans. Use the three-pass plan: Day 1 to 2 attempt all 45 MCQs, Day 3 to 5 solve the 53 two-mark and 33 three-mark questions, then in the final days re-do every question you got wrong. Always write the exact microbe name and its product.
Ques. Does the PDF give answers or only the questions?
Ans. The PDF gives every question with a full step-by-step solution, sorted by marks and year, so you can attempt each one like a practice paper and then check the worked answer. For full answers, open the NCERT Solutions page for Microbes in Human Welfare or check the official CBSE marking scheme for that year.
Ques. Is sewage treatment an important topic for the CBSE Microbes in Human Welfare questions?
Ans. Yes. Sewage treatment makes up close to a fifth of the set, and CBSE often sets the primary-then-secondary steps, flocs and BOD as a 2 or 3-mark question. Learning the order of the steps is the safest way to score this band.
Ques. What are biofertilisers?
Ans. Biofertilisers are living microbes that enrich soil nutrients. Examples include Rhizobium and Azospirillum for nitrogen, mycorrhizal fungi for phosphorus, and cyanobacteria like Anabaena in paddy fields. They cut the need for chemical fertilisers and improve soil health.
Ques. How is BOD defined?
Ans. BOD, or biochemical oxygen demand, is the amount of oxygen that microbes would use up to break down the organic matter in one litre of water. A higher BOD means more organic pollution. Treated effluent must have a low BOD before release into a river.
Ques. What are biocontrol agents?
Ans. Biocontrol agents are organisms used to control pests and diseases instead of chemical pesticides. Bacillus thuringiensis kills insect larvae, ladybird beetles eat aphids, and Baculovirus targets specific insects. They are safe for non-target species and the environment.
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