Briefly describe three types of animals on the basis of their sites of their fertilisation and development. also give one example for each.
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Answer
There are two types of fertilization in animals, viz. external fertilization and internal fertilization.
External Fertilisation: When fertilization takes place outside the animal’s body, it is external fertilization. Most of the aquatic animals show external fertilization, e.g. fish and frog. A large number of eggs need to be fertilized in this method because most of the fertilized eggs get washed away by water or are eaten by predators. A large number of eggs ensures the survival of some of the offspring.
Internal Fertilisation: When fertilization takes place inside the animal’s body, it is internal fertilization. Internal fertilization happens in most of the terrestrial animals. Unlike external fertilization, there is no need to produce a large number of eggs in internal fertilization.