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The diagram given below shows… (Class 12 Biology 2023, Q17)

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BiologyCBSE Class 12 · Board exam 2023, set 57/1/1 · 2 marks · Very short answer

CBSE Class 12 Biology 2023: question 17

Set in the CBSE Class 12 board exam of 2023, paper 57/1/1, section B, question 17, for 2 marks. Try it first; the hints and our step-by-step solution are below.

Q17 · 2 marks · Very short answerCompetency-basedHuman Reproduction

The diagram given below shows a developmental stage of human embryo. Answer the following questions with reference to it :
(a) Identify and name the human embryonic stage shown.
(b) Mention its exact location in the normal pregnancy of a woman.
(c) Write one function of each of the two parts labelled 'X' and 'Y'.

Figure in the paper: A hollow spherical embryo with an outer single layer of cells (labelled X, pointed at the outer layer) and a cluster of cells attached at the top inside (labelled Y). See it in the official paper.

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

Hints

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

Hint 1

Think of the stage that follows the morula, which has a cavity.

Hint 2

The outer cell layer and the inner cluster of cells have different jobs during implantation and development.

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) The stage is the blastocyst, a hollow ball of cells formed from the morula.

    ½ mark

  2. (b) In a normal pregnancy the blastocyst becomes embedded in the endometrium, the innermost layer of the uterine wall. This is called implantation.

    ½ mark

  3. (c) 'X' is the trophoblast, the outer layer. It attaches to the endometrium and helps the blastocyst implant in the uterus.

    ½ mark

  4. 'Y' is the inner cell mass. It differentiates to form the embryo.

    ½ mark

Answer: (a) Blastocyst; (b) endometrium of the uterus; (c) X (trophoblast) – attachment/implantation; Y (inner cell mass) – differentiates into the embryo

Where the marks are

  • Names the stage as blastocyst (½ mark)
  • States the location as the uterine wall/endometrium (½ mark)
  • Function of trophoblast X: implantation/attachment to endometrium (½ mark)
  • Function of inner cell mass Y: differentiates into the embryo (½ mark)

Revise the chapter

Practise this chapterBoard-style questions from Human Reproduction, one at a time, marked against the answer key and marking points.Back to the full paper2023 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.