▶️ Answer/Explanation
Fertilisation involves the fusion of two haploid gametes to form a diploid zygote. The key event is the fusion of the nuclei from the sperm and the egg. This nuclear fusion combines the genetic material from both parents. While the sperm’s cytoplasm and cell membrane may contribute during entry, they do not “fuse” as primary structures—the sperm membrane merges with the egg membrane, and the sperm cytoplasm enters, but the defining genetic union occurs at the nuclear level. Gametes (animal) lack cell walls, so option (B) is irrelevant.
✅ Answer: (D)
✅ Answer: (D)
▶️ Answer/Explanation
Sexual reproduction involves the fusion of haploid gamete nuclei (fertilisation) to form a zygote, which directly matches statement $4$. This process combines genetic material from two different parents, leading to genetic variation among the offspring (statement $1$). In contrast, asexual reproduction produces genetically identical clones. Statement $3$ is incorrect because sexual reproduction occurs in plants, fungi, and many other organisms, not just animals. Therefore, statements $1$ and $4$ are the only accurate descriptions provided.
✅ Answer: (B)
✅ Answer: (B)
▶️ Answer/Explanation
Detailed solution
The correct answer is B.
Reasoning:
Pollination is defined specifically as the transfer of pollen from the anther (the male part) to the stigma (the receptive female part). While pollen eventually facilitates fertilization in the ovary, the initial physical transfer ends at the stigma. Options C and D describe the growth of the pollen tube, which occurs after pollination is complete. Therefore, the movement is always from the pollen-producing anther to the pollen-receiving stigma.