Animals are classified mainly into three groups namely – Oviparous, Viviparous and Ovoviviparous depends on the site of development of embryo and whether they lay eggs (unfertilized or fertilized) or give birth to young ones.
Oviparous
In Oviparous Ovum-egg-, Parere- to produce) animals (egg laying animals), the young hatch from eggs
laid outside the mother’s body. e.g. reptiles and birds (their eggs are covered by hard calcareous shells), invertebrates, fishes and amphibians (eggs are not covered by hard calcareous shells but covered by a membrane).
Viviparous
Viviparous (L., Vivus – alive, Parere to produce) animals give rise to young ones. Viviparity is a type of development in which the young ones are born alive after being nourished in the uterus through the placenta.
Majority of mammals including human beings are viviparous.
Ovoviviparous
In Ovoviviparous animals, the embryo develops inside the egg and remains in the mother’s body until they
are ready to hatch. This method of reproduction is similar to viviparity but the embryos have no placental connection with the mother and receive their nourishment from the egg yolk. Ovoviviparity is seen in
fishes like shark.
