Revision: Reproduction in Humans Biology ICSE ICSE Class 8 CISCE

The formation of a zygote by the union of male and female gametes is known as fertilization.

The fusion of the male gamete (sperm) and female gamete (ovum) to form a zygote is called fertilisation.

or

Formation of zygote by union of sperm and ovum is called as fertilization.

1. Fertilisation is the union of sperm and ovum to form a zygote and is internal in humans.
2. During copulation, millions of sperms are ejaculated into the vagina, but only one sperm fertilises the ovum in the oviduct.
3. The acrosome of the sperm releases enzymes that help it penetrate the egg membrane; chemical changes then prevent entry of other sperms.
4. Fusion of sperm nucleus and egg nucleus restores the diploid chromosome number (46) in the zygote.
5. From puberty to menopause (45–50 years), only about 400 ova are released; ageing oocytes may lead to chromosomal abnormalities if fertilised.
6. Gametes are formed by meiosis: sperms are of two types (22+X or 22+Y), while ova are of one type (22+X); meiosis in ova completes during fertilisation.