(a) List two reasons for the appearance of variations among the progeny formed by sexual reproduction. (i) Name the part marked ‘A’ in the diagram. (ii) How does ‘A’ reaches part ‘B’? (iii) State the importance of the part ‘C’. (iv) What happens to the part marked ‘D’ after fertilisation is over?

(a) Two Reasons for Variations in Sexual Reproduction

1. Combining DNA from Two Parents: Sexual reproduction involves combining genetic material (DNA) from two different individuals, creating a completely novel combination of variants.
2. Inaccuracies in DNA Copying: The biochemical process of DNA copying during gamete formation is not absolutely accurate, introducing subtle variations in each generation.

(b) Analysis of the Pollen Germination Diagram

• (i) Name of Part 'A':

Part A is the Pollen grain.

• (ii) How 'A' reaches 'B':

The pollen grain ($A$) reaches the stigma ($B$) through the process of pollination. This transfer is achieved by external agents such as wind, water, or animals (like insects).

• (iii) Importance of Part 'C' (Pollen Tube):

Part C is the Pollen tube. Its importance is to grow out of the pollen grain, travel down through the style, and carry the male germ-cell to the ovary so it can reach and fuse with the female gamete (egg cell) inside the ovule.

• (iv) What happens to Part 'D' (Ovary/Ovule/Zygote) after fertilisation:
• If D represents the Zygote: It divides several times to form an embryo inside the ovule.
• If D represents the Ovule: It develops a tough coat and gradually converts into a seed.
• If D represents the Ovary: It grows rapidly and ripens to form a fruit (while other parts like petals and stamens shrivel and fall off).