Gamete Formation in Animals Spermatogenesis Oogenesis Both Spermatogenesis and Oogenesis involve the process of meiosis, but they take place in different ways
Spermatogenesis • The process of creating sperm. • Takes place in the Testes of most animals. • The process begins with a diploid (2n) cell called a Spermatogonium. • At the beginning of puberty, the Spermatogonia reproduce through Mitosis.
Spermatogenesis • These diploid cells then undergo Meiosis to form 4 Haploid (n) cells. • After Meiosis II, the new haploid cells undergo a final set of developmental stages. • Afterwards, the cells are mature Sperm.
Oogenesis • The process of creating egg cells • Takes place in the ovaries of most animals • The process begins with a diploid (2n) cell called an oogonium. • Oogonia reproduce by mitosis before birth and begin meiosis, but stop at Prophase I.
Oogenesis • There is an uneven distribution of cytoplasm after meiosis I. • The cell with most of the cytoplasm continues through meiosis I and II to form an egg. • The other products are called polar bodies and degenerate. • Meiosis II is not completed unless the egg is fertilized by a sperm cell.