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When a girl is born, the… (Class 10 Science 2025, Q38)

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ScienceCBSE Class 10 · Board exam 2025, set 31/2/1 · 4 marks · Case-based

CBSE Class 10 Science 2025: question 38

Set in the CBSE Class 10 board exam of 2025, paper 31/2/1, section E, question 38, for 4 marks. Try it first; the hints and our step-by-step solution are below.

Q38 · 4 marks · Case-basedCompetency-basedHow do Organisms Reproduce?

When a girl is born, the ovaries already contain thousands of immature eggs. On reaching puberty, some of these start maturing. One matured egg is released every month by one of the ovaries. The two oviducts unite into an elastic bag-like structure known as uterus.

  1. (a)

    Write the site of fertilization in human female.

    1 mark
  2. (b)

    How does the uterus prepare itself to receive and nurture the growing embryo? Explain.

    1 mark
  3. (c)(i)

    What happens when the egg is not fertilized?

    2 marks

  4. OR

    (c)(ii)

    How does the developing embryo get nutrition from the mother's blood? Explain.

    2 marks

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 31/2/1.

Hints

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

Hint 1

The egg meets the sperm on its way from the ovary to the uterus.

Hint 2

Think about what the uterus wall must provide to an implanted embryo.

Hint 3

Name the tissue that connects the embryo to the mother's uterine wall.

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) Fertilisation takes place in the oviduct (fallopian tube).

    1 mark

  2. (b) Every month, the lining of the uterus thickens and becomes spongy. It is richly supplied with blood so that it can receive and nourish an embryo if fertilisation occurs.

    1 mark

  3. (c)(i) If the egg is not fertilised, the thickened, blood-rich uterine lining is not needed. It slowly breaks down.

    1 mark

  4. (c)(i) The broken lining comes out through the vagina as blood and mucus, along with the unfertilised egg. This is menstruation, which occurs roughly every month and lasts about 2–8 days.

    1 mark

  5. (c)(ii) The embryo gets nutrition through a special disc-like tissue called the placenta, embedded in the uterine wall. Villi on the embryo's side of the placenta lie in blood spaces of the mother and provide a large surface area.

    1 mark

  6. (c)(ii) Glucose and oxygen pass from the mother's blood to the embryo through the placenta, while the embryo's wastes pass into the mother's blood to be removed.

    1 mark

Answer: (a) Oviduct (fallopian tube). (b) The uterine lining thickens, becomes spongy and gets a rich blood supply. (c)(i) The lining breaks down and is shed as blood and mucus with the egg; this is menstruation. (c)(ii) Through the placenta, which passes oxygen and nutrients from the mother's blood to the embryo.

Where the marks are

  • Site: oviduct/fallopian tube (1 mark)
  • Uterine lining thickens and gets a rich blood supply (1 mark)
  • (c)(i) Lining breaks down (1 mark)
  • (c)(i) Shed as blood and mucus with the egg, i.e. menstruation (1 mark)
  • (c)(ii) Placenta embedded in the uterine wall (1 mark)
  • (c)(ii) Oxygen and nutrients pass from mother to embryo, and wastes pass back (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from How do Organisms Reproduce?, one at a time, marked against the answer key and marking points.Back to the full paper2025 board paper, set 31/2/1: 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.