Male sperms are injected inside the body of the female partner through the reproducing organs. The sperms reach the female reproductive organs where the male gamete ( egg or ovum) fuse together to from a new called zygote. This zygote over a period of time changes into an embryo this emryo develops into a new individual. There are different ways in which the fertilized egg develops into a new organism let us study some of them. Birds lay fertilised eggs and keep the eggs warm by sitting on them. New young ones hatch put of the eggs in due course of time like birds snakes and crocodiles also lay fertilised eggs which develop into young ones. Unlike birds and reptiles cows dogs and humans give birth to fully formed young ones. In these organisms the fertilised eggs gradually develops into a mature body in the mother womb. It comes out of the womb as a fully developed young one .