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Select the option that shows… (Class 12 Biology 2023, Q12)

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BiologyCBSE Class 12 · Board exam 2023, set 57/5/1 · 1 mark · MCQ

CBSE Class 12 Biology 2023: question 12

Set in the CBSE Class 12 board exam of 2023, paper 57/5/1, section A, question 12, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q12 · 1 mark · MCQSexual Reproduction in Flowering Plants

Select the option that shows the correctly identified 'U', 'X', 'Y' and 'Z' in a developing dicot embryo.

  1. (A)X – Plumule (2n), Y – Suspensor (n), Z – Cotyledon (2n), U – Radicle (2n).
  2. (B)X – Plumule (2n), Y – Suspensor (2n), Z – Radicle (2n), U – Cotyledon (2n).
  3. (C)X – Suspensor (2n), Y – Cotyledon (2n), Z – Radicle (2n), U – Plumule (2n).
  4. (D)X – Cotyledon (2n), Y – Radicle (n), Z – Plumule (n), U – Suspensor (n).

Figure in the paper: Photograph of a developing dicot embryo (heart/curved stage): a small rounded structure at the top labelled X connected by a thin stalk to the long main body labelled Z; a curved tip on the right labelled Y; a point at the bottom left labelled U. See it in the official paper.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2023 board paper, set 57/5/1.

Hints

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

Hint 1

Recall the ploidy of all embryo parts, since they come from the zygote.

Hint 2

The thin stalk that attaches the embryo is the suspensor.

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. In a dicot embryo, the stalk-like structure attaching the embryo is the suspensor (X). The curved lobes are the cotyledons (Y), the radicle lies at the micropylar end (Z) and the plumule is the shoot apex (U).

    ½ mark

  2. All embryo parts develop from the zygote, so all are diploid (2n). This rules out the options with n. Hence option (C).

    ½ mark

Answer: (C)

Where the marks are

  • Correct identification, option (C) (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 paper2023 board paper, set 57/5/1: 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.