Science (086) — CBSE Class 10 board question

(i)

• A – Style (part of pistil connecting stigma to ovary)
• B – Pollen tube (grows down the style carrying male gametes)
• C – Egg cell / Ovule (inside the ovary)

When B reaches C: The pollen tube enters the ovule through the micropyle and releases two male gametes. One fuses with the egg cell to form a zygote (fertilisation); the other fuses with the polar nuclei to form the primary endosperm nucleus (double fertilisation).

Significance: Fertilisation leads to the formation of a zygote, which develops into an embryo, ensuring sexual reproduction and the formation of seeds and new plants.

(ii) Post-fertilisation changes in a flower:

1. The zygote develops into an embryo.
2. The ovule develops into a seed.
3. The ovary develops into a fruit.
4. The sepals, petals, stamens, and style wither and fall off.
5. The wall of the ovary (pericarp) becomes the fruit wall.

Source: Chapter 7, Section 7.3 – How do Organisms Reproduce?

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• Part (i) is worth ~3 marks: name all three parts (1 mark), explain what happens at fertilisation including double fertilisation (1 mark), and state significance (1 mark).
• Part (ii) is worth ~2 marks: list at least 4–5 post-fertilisation changes concisely. Examiners expect: zygote→embryo, ovule→seed, ovary→fruit, and floral parts withering.
• "Double fertilisation" is a key term examiners reward — don't omit it.
• Keep post-fertilisation changes as a neat list; that format is clear and scores well.