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Given below is a set… (Class 12 Biology SQP 2025-26, Q29)

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BiologyCBSE Class 12 · Sample paper, session 2025-26 · 4 marks · Case-based

CBSE Class 12 Biology sample paper 2025-26: question 29

From the official CBSE sample question paper for 2025-26, section D, question 29, for 4 marks. Try it first; the hints and our step-by-step solution are below.

Q29 · 4 marks · Case-basedCompetency-basedSexual Reproduction in Flowering Plants

Given below is a set of information about some fruits and seeds.

FruitFruit and seed formation
PNucellar cells surrounding the embryo sac develop into embryos.
QOvary develops into the fruit by the application of growth hormones.
RThalamus contributes to fruit formation.
SOvary matures into a fruit after fertilisation.

On the basis of the information provided above, answer the following questions with justification for each answer.

  1. A

    How many embryo sacs will be present in each ovule of S before maturation and how many egg(s) will be present in each embryo sac when the embryo sac is developed from a single megaspore?

    1 mark
  2. B

    (i) Which of these fruits exhibits polyembryony? Will their embryos exhibit genetic variation? Justify.
    (ii) What will be ploidy of the embryonic cells in the above case?

    2 marks
  3. C

    Which of these fruits can be considered as parthenocarpic? Give a reason.

    1 mark

  4. OR

    D

    Which of the fruits P, Q, R or S is a true fruit with seeds? Give reason.

    1 mark

Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2025-26.

Hints

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

Hint 1

Recall the monosporic, 7-celled, 8-nucleate embryo sac.

Hint 2

Nucellar cells are somatic – what is their ploidy, and is meiosis involved?

Hint 3

Parthenocarpy means fruit formation without fertilisation; a true fruit comes only from the ovary.

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. Each ovule of S has one embryo sac. When the embryo sac develops from a single functional megaspore (monosporic development), it is 7-celled and 8-nucleate and has one egg cell in the egg apparatus.

    1 mark

  2. B(i) P shows polyembryony, because nucellar cells develop into several embryos in one seed. These embryos form by apomixis, an asexual process involving only mitosis, so they show no genetic variation: they are clones of the mother plant.

    1 mark

  3. B(ii) Nucellar cells are diploid somatic cells, so the embryonic cells are diploid (2n).

    1 mark

  4. C. Q is parthenocarpic. Its ovary develops into a fruit under growth hormones without fertilisation, so the fruit is seedless.

    1 mark

  5. D (alternative to C). S is a true fruit with seeds. It develops from the ovary after fertilisation, and the fertilised ovules mature into seeds. (R is a false fruit, since the thalamus contributes to it.)

Answer: A. One embryo sac, one egg; B(i) P – no genetic variation (apomictic); (ii) 2n; C. Q (formed without fertilisation, seedless); D. S (from ovary after fertilisation).

Where the marks are

  • One embryo sac per ovule and one egg per embryo sac (1 mark)
  • P shows polyembryony; no variation as formed by apomixis (1 mark)
  • Embryonic cells diploid (2n) (1 mark)
  • C: Q parthenocarpic as formed without fertilisation / D: S true fruit from fertilised ovary (1 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 paperSample paper 2025-26: 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.