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Answer the following. (Class 12 Biology 2025, Q17B)

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BiologyCBSE Class 12 · Board exam 2025, set 57/1/1 · 2 marks · Very short answer

CBSE Class 12 Biology 2025: question 17(B)

Set in the CBSE Class 12 board exam of 2025, paper 57/1/1, section B, question 17(B), for 2 marks. Try it first; the hints and our step-by-step solution are below.

Q17(B) · 2 marks · Very short answerMicrobes in Human Welfare

Answer the following.

  1. (i)

    Name an alcoholic drink which is produced by the help of microbes :
    (1) With distillation
    (2) Without distillation

    0 marks
  2. (ii)

    Explain how cyanobacteria can be used as bio-fertilizer.

    0 marks

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 57/1/1.

Hints

Open one hint at a time and try again before the next.

Hint 1

Fermentation by yeast gives drinks of two types. Some are distilled and some are not.

Hint 2

For cyanobacteria, think about which element they make available to plants and what else they leave in the soil.

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

  1. (i)(1) With distillation: whisky, brandy or rum. These are made by distilling the fermented broth produced by yeast (Saccharomyces cerevisiae).

    ½ mark

  2. (i)(2) Without distillation: wine or beer.

    ½ mark

  3. (ii) Cyanobacteria such as Anabaena, Nostoc and Oscillatoria are autotrophic microbes that fix atmospheric nitrogen in the soil and in paddy fields.

    ½ mark

  4. They also add organic matter to the soil, which increases its fertility. So they serve as a natural biofertiliser.

    ½ mark

Answer: (i)(1) Whisky/brandy/rum; (2) wine/beer. (ii) Cyanobacteria fix atmospheric nitrogen and add organic matter to soil, increasing fertility.

Where the marks are

  • Names one distilled drink: whisky/brandy/rum (½ mark)
  • Names one undistilled drink: wine/beer (½ mark)
  • Cyanobacteria fix atmospheric nitrogen (½ mark)
  • They add organic matter and increase soil fertility, e.g. in paddy fields (½ mark)

Revise the chapter

Practise this chapterBoard-style questions from Microbes in Human Welfare, one at a time, marked against the answer key and marking points.Back to the full paper2025 board paper, set 57/1/1: every question, by section.

The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.