Fertilization (Encyclopedia of Science)
Fertilization is the process by which the nucleus of a sperm (a male reproductive cell) fuses (combines) with the nucleus of an egg (a female reproductive cell; also called an ovum). Fertilization occurs somewhat differently in plants and animals. In flowering plants, two sperm cells are involved in the process of fertilization. The first sperm cell combines with an egg cell, while the second sperm cell combines with two nuclei present in the ovule (the structure that eventually becomes the seed). The structure formed in the second fertilization eventually forms a storage site for nutrients needed by the fertilized egg cell.
A fertilized egg cell is known as a zygote. Once formed, the zygote undergoes continuous cell division that eventually produces a new multicellular organism.
Fertilization in humans
In humans, fertilization occurs in the fallopian tubes of the female reproductive tract. It takes place within hours following sexual intercourse. Approximately 300 million sperm are released into a female's vagina during intercourse. However, only one of these sperm can...
(The entire section is 685 words.)
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