Gametogenesis: Spermatogenesis and Oogenesis Gametogenesis • Occurs in the GONADS of males and females (ovaries/testes). • In some organisms...called Hermaphrodites (like Earthworms) have BOTH male and female gonads. Spermatogenesis • Production of sperm: – Continuous and prolific (produces large numbers) • Occurs in the Testes. What happens is … • Spermatogonia (stem cells that give rise to sperm). • Spermatogonia are diploid (2n). • 4 cells result: – Develop into “MATURE” sperm – ALL ARE Haploid (n) Spermatogenesis Oogenesis • The development of ova: – Mature, “unfertilized” eggs cells – Happens in the ovary • Oogonia (stem cells that give rise to ova). Oogenesis Occurs once a month after puberty Major Difference #1 • Unevenness in the meiotic division/cytokinesis of oogenesis. – 3 polar bodies which degenerate. – Spermatogenesis = four mature sperm. Major Difference #2 • The cells that produce sperm continue to divide by meiosis throughout LIFE(males). • Not the case for women *BORN with all the PRIMARY oocytes. Major Difference #3 • Oogenesis has LONG resting periods. • Sperm is produced in an uninterrupted sequence. FERTILIZATION: • the UNION or “joining” of egg and sperm. • Monoploid (n) sperm to join with monoploid egg (n) to create a diploid (2n) number of chromosomes. • New organism WILL NOT BE IDENTICAL TO THE PARENT (SEXUAL- REPRODUCTION). • Fertilization CAN BE internal or external!!! • ***Internal Fertilization occurs within a female. Female reproductive system provides the perfect environment for sperm to survive. FERTILIZATION Continued… • Internal fertilization occurs in most land dwelling animals…such as… • -Reptiles • -Birds • -mammals External fertilization occurs within a water (aqueous) environment and egg and sperm meet in the water. (ex. FISH/Frogs) External Fertilization Example:.