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"A fully developed foetus… (Class 12 Biology 2025, Q18a)

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BiologyCBSE Class 12 · Board exam 2025, set 57/7/1 · 2 marks · Very short answer

CBSE Class 12 Biology 2025: question 18(a)

Set in the CBSE Class 12 board exam of 2025, paper 57/7/1, section B, question 18(a), for 2 marks. Try it first; the hints and our step-by-step solution are below.

Q18(a) · 2 marks · Very short answerHuman Reproduction

"A fully developed foetus initiates its delivery from the mother's womb." Explain.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 57/7/1.

Hints

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

Hint 1

Think of the neuroendocrine mechanism of parturition.

Hint 2

Name the reflex and the hormone released from the mother's pituitary.

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. The signals for parturition come from the fully developed foetus and the placenta.

    ½ mark

  2. These signals cause mild uterine contractions, called the foetal ejection reflex.

    ½ mark

  3. The foetal ejection reflex triggers the release of oxytocin from the maternal pituitary.

    ½ mark

  4. Oxytocin acts on the uterine muscle and causes stronger uterine contractions, which expel the baby. So the foetus itself starts its own delivery.

    ½ mark

Answer: Signals from the mature foetus and placenta set off the foetal ejection reflex, which releases oxytocin; oxytocin causes strong uterine contractions that deliver the baby.

Where the marks are

  • Signals arise from the fully developed foetus and placenta (½ mark)
  • Mild contractions called the foetal ejection reflex (½ mark)
  • Release of oxytocin from the maternal pituitary (½ mark)
  • Stronger uterine contractions leading to delivery (½ mark)

Revise the chapter

  • Chapter: Human Reproduction (notes, formulas, where marks are lost and every past question)
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 57/7/1: 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.