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Given below are certain… (Class 10 Science 2026, Q16a)

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ScienceCBSE Class 10 · Board exam 2026, set 31/1/1 · 5 marks · Long answer

CBSE Class 10 Science 2026: question 16(a)

Set in the CBSE Class 10 board exam of 2026, paper 31/1/1, section A, question 16(a), for 5 marks. Try it first; the hints and our step-by-step solution are below.

Q16(a) · 5 marks · Long answerCompetency-basedHow do Organisms Reproduce?

Given below are certain situations. Analyse each and describe its possible impact:

  1. (i)

    A population of bacteria living in temperate waters whose temperature increased by global warming.

    0 marks
  2. (ii)

    The sperm encounters the egg when it reaches the oviduct in human females.

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  3. (iii)

    Self pollination does not occur in a flower that contains only pistil.

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  4. (iv)

    Egg does not get fertilised in a human female.

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  5. (v)

    When the seed is placed under appropriate condition of water and air in the soil?

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Source: official question paper from cbse.gov.in (PDF). See it in the full 2026 board paper, set 31/1/1.

Hints

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

Hint 1

Link (i) to variation helping survival.

Hint 2

For (iv), think about what happens to the uterine lining each month.

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. (i) Most bacteria in the population would die in the warmer water. A few variants that can tolerate heat would survive and multiply, so the population would come to be dominated by heat-resistant bacteria. Variation helps survival.

    1 mark

  2. (ii) The sperm fuses with the egg, so fertilisation takes place and a zygote is formed. The zygote later develops into an embryo.

    1 mark

  3. (iii) The flower is unisexual (only pistil), so self-pollination is impossible. It can produce fruit only if cross-pollination occurs; otherwise there is no fertilisation and no fruit or seed formation.

    1 mark

  4. (iv) The thick, spongy uterine lining prepared for the embryo is not needed. It breaks down and comes out through the vagina as blood and mucus, which is menstruation.

    1 mark

  5. (v) The seed germinates: the embryo grows into a seedling (radicle forms the root, plumule forms the shoot).

    1 mark

Answer: (i) Most die, heat-resistant variants survive; (ii) fertilisation, zygote forms; (iii) only cross-pollination can lead to fruit, else no fertilisation; (iv) menstruation; (v) germination into a seedling.

Where the marks are

  • Heat-resistant variants survive (1 mark)
  • Fertilisation forms zygote (1 mark)
  • Cross-pollination needed / no fertilisation or fruit (1 mark)
  • Uterine lining sheds – menstruation (1 mark)
  • Seed germinates into seedling (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 paper2026 board paper, set 31/1/1: 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.