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The following question is… (Class 12 Biology 2025, Q30)

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BiologyCBSE Class 12 · Board exam 2025, set 57/7/1 · 4 marks · Case-based

CBSE Class 12 Biology 2025: question 30

Set in the CBSE Class 12 board exam of 2025, paper 57/7/1, section D, question 30, for 4 marks. Try it first; the hints and our step-by-step solution are below.

Q30 · 4 marks · Case-basedCompetency-basedSexual Reproduction in Flowering Plants

The following question is based on pollination. Study the figures carefully and answer the questions that follow.

  1. (a)

    Give the scientific terms for the processes taking place in Figures A and B respectively.

    1 mark
  2. (b)

    Mention two conditions necessary for the process occurring in Figure B.

    2 marks
  3. (c)(i)

    State one advantage and one disadvantage of the process occurring in Figure B.

    1 mark

  4. OR

    (c)(ii)

    Name one plant where, in some flowers only, the process in Figure B takes place and give the reason responsible for it.

    1 mark

Figure in the paper: Figure A: two flowers on different branches with pollen transferring between them (pollens shown moving from one flower to the other). Figure B: a single pea-type flower with a red arrow showing pollen from anthers moving to the stigma of the same flower; ovary with ovules visible. See it in the official paper.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 57/7/1.

Hints

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

Hint 1

Compare where the pollen comes from in each figure: another flower or the same flower.

Hint 2

For self-pollination within one flower, think about timing and the position of the anthers and stigma. Some plants have flowers that never open.

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. (a) Figure A shows pollen moving between two flowers on the same plant (different branches): Geitonogamy.

    ½ mark

  2. Figure B shows pollen moving from the anther to the stigma of the same flower: Autogamy.

    ½ mark

  3. (b) Condition 1: the release of pollen and the receptivity of the stigma must be synchronised.

    1 mark

  4. Condition 2: the anthers and stigma must lie close to each other in a bisexual flower, or the flower should be cleistogamous (closed).

    1 mark

  5. (c)(i) Advantage: seed set is assured even without pollinators, and pure lines are maintained.

    Disadvantage: there is no genetic variation, and continued self-pollination leads to inbreeding depression.

    1 mark

  6. (c)(ii) Plant: Viola (common pansy), Oxalis or Commelina.

    Reason: these plants produce some cleistogamous flowers that never open. The anthers and stigma lie close together inside the closed flower, so only autogamy can occur.

    1 mark

Answer: (a) A: Geitonogamy, B: Autogamy; (b) synchronised pollen release and stigma receptivity, and anthers close to the stigma; (c)(i) assured seed set but no variation (inbreeding depression); (c)(ii) Viola/Oxalis/Commelina, because of closed cleistogamous flowers.

Where the marks are

  • A: Geitonogamy (½ mark)
  • B: Autogamy (½ mark)
  • Two conditions for autogamy (1 + 1 mark)
  • (c)(i) One advantage (½ mark) and one disadvantage (½ mark), OR (c)(ii) plant name (½ mark) and cleistogamy as the reason (½ mark)

Revise the chapter

Practise this chapterBoard-style questions from Sexual Reproduction in Flowering Plants, one at a time, marked against the answer key and marking points.Back to the full paper2025 board paper, set 57/7/1: 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.