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Assertion (A)… (Class 10 Science SQP 2024-25, Q18)

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ScienceCBSE Class 10 · Sample paper, session 2024-25 · 1 mark · Assertion-reason

CBSE Class 10 Science sample paper 2024-25: question 18

From the official CBSE sample question paper for 2024-25, section A, question 18, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q18 · 1 mark · Assertion-reasonCompetency-basedHow do Organisms Reproduce?

Assertion (A): Generally, the number of chromosomes in a cell and in a germ cell is not the same in species.
Reason (R): When two germ cells combine, they restore the normal number of chromosomes in a species.

  1. (A)Both A and R are true, and R is the correct explanation of A.
  2. (B)Both A and R are true, and R is not the correct explanation of A.
  3. (C)A is true but R is false.
  4. (D)A is false but R is true

Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2024-25.

Hints

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

Hint 1

How many chromosomes does a gamete have compared with a body cell?

Hint 2

Why does the number have to be halved?

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. Germ cells are formed by halving the chromosome number, so they carry half the chromosomes of a body cell. A is true.

    ½ mark

  2. At fertilisation, two germ cells fuse and restore the full chromosome number. This is exactly why germ cells must carry half the number, so R is true and explains A. The answer is option (A).

    ½ mark

Answer: Both true, R explains A; option (A)

Where the marks are

  • Recognises both statements as true and that R explains A (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 paperSample paper 2024-25: 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.