(a) Identify A, B and C in the given diagram and write their functions. (b) Mention the role of gamete and zygote in sexually reproducing organisms.

(a) Identification and Functions of A, B, and C

Based on the structure of the female reproductive organ (pistil) in a flower:

1. A — Stigma:

• Function: It is the terminal, sticky part of the pistil. It serves as the landing platform that receives pollen grains during pollination.

1. B — Style:

• Function: It is the middle elongated tube-like part of the pistil. It provides a pathway through which the pollen tube grows to reach the ovary.

1. C — Ovary:

• Function: It is the swollen bottom part of the pistil containing ovules. Each ovule contains an egg cell (female gamete). It is the site where fertilisation occurs, leading to zygote formation. Post-fertilisation, the ovary develops into a fruit.

(b) Role of Gamete and Zygote in Sexually Reproducing Organisms

• Role of Gamete (Germ-cell):
• Gametes are specialised reproductive cells (male and female) that contain only half the number of chromosomes and half the amount of DNA ($1n$) compared to non-reproductive body cells ($2n$).
• This reduction is achieved through meiosis. When the male and female gametes fuse during fertilisation, they restore the original diploid number of chromosomes and DNA content in the next generation, maintaining genomic stability across the species.
• Role of Zygote:
• The zygote is the single diploid cell ($2n$) formed by the fusion of male and female gametes.
• It serves as the vital link between two generations. It contains sufficient stores of energy and the complete genetic blueprint required to divide, grow, and develop into a new multicellular organism with highly specialised tissues and organs.