Q.12 Define fertilization and explain its types.
Fertilization
Answer:
After the formation of gametes; fertilization occurs. There are two ineca. hanisms by which fertilization can take place:
(1) External fertilization:
Introduction
In external fertilization, egg cells are fertilized outside the body.
Explanation
It occurs in aquatic environment and both the male and female animals release their gametes in. their surroundings at almost the same time. In external fertilization, there is risk of loss of gametes due to environmental hazards such as predators.
Examples
It occurs in many invertebrates and the first two groups of vertebrates i.e. fishes and amphibians

Internal fertilization
Introduction
Egg cells are fertilized within the reproductive tract of fr male.
Explanation
Such animals provide protection to the developing embryo. After fertilization, reptiles and birds make protective shells around their egg.cells and then lay these eggs. Extra protection is provided to embryo and mother supplies all that embryo needs: An mammals, the development of fertilized egg into new body takes place within the mother’s body.
Examples
Examples are reptiles, birds and mammals