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Class 10 Science: How do Organisms Reproduce?, 8 practice questions with answers

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These are 8 practice questions on NCERT Class 10 Science Chapter 7, How do Organisms Reproduce?, each with a short answer and the textbook page it comes from. They cover the ways single organisms and plants reproduce (fission, budding, vegetative propagation, spores), how many chromosomes a gamete carries, pollination, and two numericals on repeated division. Try each one before you read the answer. For the hormones that coordinate a plant or an animal, see the Class 10 Control and Coordination questions.

These questions are our own, drafted with AI help. Every number was re-computed by a test script and every statement was checked against the chapter, but no practising teacher has reviewed them yet. If you find a mistake, please tell us.

Reproduction without gametes

Question 1. How does Amoeba reproduce? (By binary fission; by budding; or by seeds.)

Answer: by binary fission. Amoeba splits into two cells during cell division, and the splitting can take place in any plane. (Section 7.2.1, page 115.)

Question 2. Hydra uses its regenerative cells to reproduce by which method? (Budding; pollination; or spore formation in a sporangium.)

Answer: budding. In Hydra, a bud develops as an outgrowth due to repeated cell division at one specific site; the bud grows into a tiny individual and, when mature, detaches from the parent to become a new independent individual. (Section 7.2.4, page 117.)

Question 3. Assertion (A): New Bryophyllum plants can grow from buds on the edges of its leaves. Reason (R): Bryophyllum can reproduce only through seeds. Choose the correct option: both true and R explains A; both true but R does not explain A; A true and R false; or A false and R true.

Answer: A is true and R is false. The buds produced in the notches along the leaf margin of Bryophyllum fall on the soil and develop into new plants, a kind of vegetative propagation, so a Bryophyllum does not reproduce only through seeds. (Page 118, with vegetative propagation in section 7.2.5, page 117.)

Question 4. Rhizopus, the bread mould, reproduces through tiny blob-on-a-stick structures. What are the blobs called, and by what method does the mould reproduce?

Answer: sporangia; spore formation. The blobs are sporangia, which contain cells, or spores, that can develop into new Rhizopus individuals. The spores have thick walls that protect them until they reach a moist surface. (Section 7.2.6, page 118.)

Sexual reproduction

Question 5. The body cells of an organism have 20 chromosomes. How many chromosomes do its gametes have?

Answer: 10. Gametes (germ-cells) are made by meiosis and carry half the number of chromosomes of the non-reproductive body cells: 20 ÷ 2 = 10. (Page 120.)

Question 6. In a flower, pollen is transferred from the stamen to the stigma of the same flower. What is this transfer called, and what is it called if the pollen goes to another flower?

Answer: self-pollination; cross-pollination. Pollen transferred in the same flower is self-pollination; pollen transferred from one flower to another, by agents such as wind, water or animals, is cross-pollination. (Page 121.)

Repeated division: two numericals

Question 7. An Amoeba reproduces by binary fission. Starting from one Amoeba, how many are there after 3 rounds of division, if every cell divides each time?

Answer: 8. Each division doubles the number: 1 → 2 → 4 → 8, which is 2³ = 8. (Binary fission, page 115; the counting is ours.)

Question 8. Assume a bacterium splits into two every 20 minutes. Starting from one bacterium: (a) how many are there after 2 hours? (b) how many after 3 hours? (c) after how many minutes are there more than 1,000 bacteria for the first time?

Answer: (a) 2 hours = 120 minutes = 6 divisions, so 2⁶ = 64. (b) 3 hours = 180 minutes = 9 divisions, so 2⁹ = 512. (c) 2¹⁰ = 1,024 is the first power of 2 above 1,000, so 10 divisions are needed: 10 × 20 = 200 minutes. (The textbook says bacteria and protozoa simply split into two halves during cell division, page 115; the 20-minute rate is an assumption of this question.)

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Sources

All opened and read on 21 October 2026. Page numbers are the printed page numbers of the textbook.

The facts are from the textbook pages above. The questions, worked answers and checks are our own, and every number was re-computed by script. This guide is general information; follow your teacher and the textbook.