Microbes in Human Welfare: Class 12 Previous Year Questions

Microbes in Human Welfare questions asked in CBSE board exams

Repeated questions first. Open the free app to see each question as it appeared in the paper, with its marking scheme.

1. _________ Page 13 of 24 { } 19. After significant reduction of BOD during secondary treatment of sewage, what further processes are carried out ? Mention any one important outcome of these processes. 1½+½ _________ Page 14 of 24 { } 20. (a)    …
   Board 20262 marksshort answer
2. 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.
   Board 20261 markAssertion-Reason
3. _________ Page 11 of 24 { } 14. Assertion (A) : Microbes are used for commercial production of alcohol and beverages. 1 Reason (R) : Yeast converts glucose into ethanol and carbon dioxide during fermentation. _________ Page 12 of 24 { } 15.  (A) : .…
   Board 20261 markAssertion-Reason
4. Match the items in Column-A with that of Column-B : Column-A Column-B (i) Lady bird beetle (a) Methanobacterium (b) (i) Mycorrhiza Trichoderma (ii) Biological control (c) Aphids (iv)Biogas (d) Glomus Choose the option that matches the items of Column A with th…
   Board 20251 markMCQ
5. For commercial and industrial production of citric acid, which one of the following microbes is used ? (B) Aspergillus niger (A) Lactobacillus sp. (C) Clostridium butylicum (D) Saccharomyces cerevisiae
   Board 20251 markMCQ
6. Write the basic steps followed in the Assisted Reproductive Technologies (ART) programme to help childless couples. Why is it also known as test tube baby programme ?
   Board 20242 marksshort answer
7. The graph plotted below is based on the data collected by biology students with respect to the levels of oxygen at the specific points in the river flowing outside their city. Which point in the graph indicates the entry of untreated sewage in the river ? (a) …
   Board 20231 markMCQ
8. State the impact of constant mechanical agitation and pumping of air in the aeration tank on the sewage during the biological treatment. OR (a) Cattle excreta is important source for producing a domestic fuel. Name the fuel and write its main components. (b) W…
   Board 20221 markvery short
9. (a) Give an example of viral biocontrol agent. (b) Why are they considered to be desirable when an ecologically sensitive area is being treated ?
   Board 20221 markvery short
10. Study the given diagrams of Biogas plants questions that follow : Which one of the two biogas plants can be used for generating gas fuel and electricity and why ? Give suitable reasons in support of your answer.
    Board 20221 markvery short
11. a) Why is it important to measure biochemical oxygen demand (BOD) of the effluent? At what stage of sewage treatment is this testing done? b) BOD level of three samples of water labelled as A, B and C are 60 mg/L, 20 mg/L and 500 mg/L respectively. Which sampl…
    CBSE practice 2023-243 marksshort answer
12. Look at the labelled diagram of the male reproductive system. Identify the correct route of passage of sperm in the male reproductive tract. A. P-Q-R-S B. S-Q-R-P C. P-S-R-Q D. Q-R-S-P
    CBSE practice 2021-221 markMCQ
13. Two statements are given - one labeled Assertion (A) and the other labeled Reason (R). Assertion: INVO cell is a new cost-effective technology for in vitro fertilisation (IVF) in which the sperm and the egg are mixed in a lab, put in a small capsule which is i…
    CBSE practice 2021-221 markAssertion-Reason
14. *There is no change in the Question Paper Design and Assessment Pattern for Academic Session 2026-27. 11 A biotechnology company grew Streptomyces in a fermenter to produce an antibiotic. It was observed that Day 7 onwards, the actual yield drops sharply, even…
    Sample paper 2026-271 markMCQ
15. Assertion (A): The primary goal of sewage treatment is to eliminate all organic matter from the effluent. Reason (R): High BOD indicates a low level of organic matter in the water, which can lead to increased oxygen consumption by microorganisms, potentially h…
    Sample paper 2026-271 markAssertion-Reason

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