This document summarizes the key stages of reproduction: 1) Gamates are formed through meiosis in both males and females, producing eggs in females and sperm in males. 2) Fertilization occurs when sperm travels through the female's reproductive system to meet and penetrate the egg, forming a zygote. 3) Cleavage occurs as the zygote divides into many cells called blastomeres through rapid cell division. Later cleavage forms more than 16 cells. 4) Blastula formation results in blastomeres surrounding a fluid-filled cavity called a blastocoel.