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Spermatogenesis is the process in which sperms are produced from spermatogonia in testes,it start at the age of puberty as a result of marked rise in gonadotropin releasing hormone while in  oogenesis eggs are produced from oogonia inside the ovary, it occurs at the time of embryonic development in females, the former involves equal cytoplasmic division and produce motile gametes while the latter involves unequal cytoplasmic division and produce non-motile gametes.