Skip to content

Study the graphs given below… (Class 12 Biology 2025, Q29)

questionbuddy.in/q/cbse-12-biology-2025-57-1-1-q29-graphs-showing-different-levels-certain

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

CBSE Class 12 Biology 2025: question 29

Set in the CBSE Class 12 board exam of 2025, paper 57/1/1, 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-basedHuman Reproduction

Study the graphs given below for Case 1 and Case 2 showing different levels of certain hormones and answer the question that follows :

  1. (a)

    Which hormone is responsible for the peak observed in Case 1 and Case 2 ? Write one function of that hormone.

    1 mark
  2. (b)

    Write changes that take place in the ovary and uterus during follicular phase.

    1 mark
  3. (c)

    Name the hormone Q of Case 2. Write one function of hormone Q.

    2 marks

  4. OR

    (d)

    Which structure in the ovary will remain functional in Case 2 ? How is it formed ?

    2 marks

Figure in the paper: Two graphs across follicular phase and luteal phase with ovulation marked by a dashed line. Case 1: hormone P rises sharply to a peak just before ovulation then falls; hormone Q rises after ovulation to a broad hump in the luteal phase then declines. Case 2: P peaks before ovulation then falls; Q rises steadily and stays high through the luteal phase; a curve labelled HCG begins to rise late in the luteal phase. See it in the official paper.

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

Hints

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

Hint 1

Which pituitary hormone surges in mid-cycle just before ovulation?

Hint 2

In Case 2, hCG appears. What does that say about pregnancy, and which hormone must stay high?

Hint 3

Think about what happens to the follicle after it releases the egg.

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 peak is caused by luteinising hormone (LH), called the LH surge.

    ½ mark

  2. Function: it induces rupture of the Graafian follicle, which releases the ovum (ovulation).

    ½ mark

  3. (b) Ovary: primary follicles grow into a fully mature Graafian follicle.

    1 mark

  4. Uterus: the endometrium regenerates and proliferates (thickens).

    1 mark

  5. (c) Q = progesterone.

    ½ mark

  6. Function: it maintains the endometrium and so maintains pregnancy.

    ½ mark

  7. (d) (alternative to (c)) The corpus luteum remains functional in Case 2, because hCG keeps it going during pregnancy.

    ½ mark

  8. It is formed from the remaining cells of the ruptured Graafian follicle after ovulation.

    ½ mark

Answer: (a) LH; it induces ovulation. (b) Ovary: follicles mature into a Graafian follicle; uterus: endometrium proliferates. (c) Progesterone; it maintains the endometrium/pregnancy. (d) Corpus luteum, formed from the ruptured Graafian follicle after ovulation.

Where the marks are

  • Names LH (½ mark) and gives its function, ovulation (½ mark)
  • Ovary change: maturation of follicles into a Graafian follicle (1 mark)
  • Uterus change: proliferation of the endometrium (1 mark)
  • (c) Progesterone (½ mark) and its role in maintaining pregnancy/endometrium (½ mark), OR (d) corpus luteum (½ mark) formed from the ruptured Graafian follicle (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 paper2025 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.