Fertilization (also known as conception, fecundation, syngamy and impregnation) is the fusion of gametes to initiate the development of a new individual organism. In animals, the process involves the fusion of an ovum with a sperm, which first creates a zygote and then leads to the development of an embryo. Depending on the animal species, the process can occur within the body of the female in internal fertilization, or outside (external fertilization). The cycle of fertilization and development of new individuals is called sexual reproduction.