Lifecycle of Human

• In the male reproductive organ, the testes, spermatogonial cells divide mitotically forming a group of diploid primary spermatocytes.
• Each primary spermatocyte divides meiotically forming two secondary spermatocytes in the first reductional division. Each secondary spermatocyte divides meiotically forming two spermatids.
• Finally, spermatid develops into spermatozoa, which is the male gamete. Thus, one primary spermatocyte yields 4 haploid sperm cells.
• In the female, oogonial cells in the ovary produces a group of diploid primary oocytes.
• Each oocyte divides meiotically forming two secondary oocytes in the first reductional division.
• The first polar body yields two polar bodies again. The big secondary oocyte produces an ovum and a polar body.
• Altogether, here are three polar bodies, which are non-functional. Thus, at the last, one primary oocyte yields only one haploid ovum cell, which is functional.
• The fusion of male gamete (Sperm) and female gamete (Ovum) forms a zygote. Then the zygote develops into man/women.