AP BIOLOGY

Detailed explanation-1: -Fertilisation occurs when the fern’s egg and sperm combine to form a zygote. Ferns require water to enable the movement of the sperm to reach the egg. A zygote is a combination of genetic material from both the egg and sperm and contains a complete set of DNA to form a new fern plant.

Detailed explanation-2: -Male and female reproductive structures develop on the lower surface of the same, or more often, on different gametophyte plants. At sexual maturity, the male structures release sperm that swim through the film of water of the moist habitat to fertilize the egg in the female structure.

Detailed explanation-3: -The gametophytes produce gametes (eggs and sperm). Fusion of gametes (fertilization) produces a zygote. The zygote grows into the next generation of sporophyte.

Detailed explanation-4: -At first glance, angiosperms may appear to have a diplontic life cycle because the gametophyte generation has been reduced to just a few cells (Figure 20.4). However, mitotic division still follows meiosis in the sporophyte, resulting in a multicellular gametophyte, which produces eggs or sperm.

Detailed explanation-5: -The female structure, called an archegonium, contains a single egg. The male structure, the antheridium, contains many flagellated sperm. The sperm are released from the antheridium and swim through a thin film of water to a nearby archegonium to fertilize the egg.