Oviparous animals lay fertilised or unfertilized eggs. The fertilized eggs remain covered by hard calcareous shell and laid in safe place in the environment. After a period of incubation young ones hatch out. Chances of survival of young ones is less as the female lay egg in the open environment. Viviparous animals Viviparous animals birth to young ones. The fertilised egg (zygote) develop into a young one inside the body of the female organism. Chances of survival of young one is more because of proper embryonic care and protection inside the mother’s body.