How an egg cell and a sperm develop into a fetus?

Answer 1

The Sperm cell swims up to the Egg cell and its head burrows into it, depositing the material in the head into the Egg cell's nucleus. At this point the Egg cell becomes an embryo and no other Sperms can enter it. It also begins to undergo cell division forming a very small fetus which grows either feeding off the yolk of the Egg or in mammals off the mother's blood supply (through the placenta).

Answer 2

When a sperm fertilizes an egg, it forms a single cell called a zygote. This zygote undergoes a process called cleavage, where it divides and forms more cells. These cells continue to divide and differentiate, forming different tissues and organs. As the embryo develops, its structures and systems begin to form, including the nervous system, respiratory system, digestive system, and so on, leading to the development of a fetus.