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In the post-fertilizati… (Class 12 Biology SQP 2026-27, Q23)

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BiologyCBSE Class 12 · Sample paper, session 2026-27 · 3 marks · Short answer

CBSE Class 12 Biology sample paper 2026-27: question 23

From the official CBSE sample question paper for 2026-27, section C, question 23, for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q23 · 3 marks · Short answerCompetency-basedSexual Reproduction in Flowering Plants

In the post-fertilization embryo sac shown in figure, structure 'P' results from the fusion of one male gamete with the egg cell, and structure 'Q' results from the fusion of the other male gamete with the polar nuclei.

A. Identify structure 'P' and structure 'Q' and state their ploidy.
B. Evaluate the following statement: "The division of 'P' always precedes the division of 'Q'." Justify your evaluation based on the nutritional requirements for seed development.
C. Which characteristic feature of endosperm helps in its nutritive role?

Figure in the paper: Figure: Fertilised embryo sac in a flowering plant. Elongated sac with degenerating synergids at the top, structure P (small nucleus) near the top, structure Q (large nucleus) at the centre, and degenerating antipodals at the bottom. See it in the official paper.

Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2026-27.

Hints

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

Hint 1

Double fertilisation gives two products: syngamy and triple fusion.

Hint 2

An embryo needs food before it can develop. Which product supplies it?

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. P = zygote, which is diploid (2n). Q = primary endosperm nucleus (PEN), which is triploid (3n).

    1 mark

  2. B. The statement is false. The PEN (Q) divides before the zygote (P) to form the endosperm. The endosperm must be ready first because it provides nourishment to the developing embryo.

    1 mark

  3. C. The cells of the endosperm are filled with reserve food materials. These act as the main source of nutrition for the developing embryo.

    1 mark

Answer: A. P = zygote (2n), Q = PEN (3n). B. False: the PEN divides before the zygote, to provide nutrition. C. Endosperm cells are filled with reserve food.

Where the marks are

  • Identifies the zygote (2n) and PEN (3n) (1 mark)
  • Statement false: the PEN divides earlier to nourish the embryo (1 mark)
  • Endosperm cells are rich in reserve food materials (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 2026-27: 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.