THE FROG

Fertilisation

• In early spring after the rain, the male frogs go to a suitable dam or pool. They croak to attract the females.


• When the eggs in the body of the female are ripe, she enters the water.


• The male clings to the female. He climbs on her back and puts his forelegs around her body.


• The female then lays her eggs in the water.


• The male now pours his male fluid over them. This male fluid contains very tiny living things which we call sperms.


• We say that the male and female mate.


• When a sperm has joined with an egg, we say the egg has been fertilised. The egg is now fertile.


• The jelly around the eggs of a frog swells and sticks to a plant. The eggs of each female are laid together in a group.


• In each egg which has been fertilised, an embryo develops.


• The embryo grows and becomes a tadpole.


• The tadpole hatches from the egg, but lives on the yolk of the egg until it has been used up.


• A tadpole lives in the water.


• The tadpole grows and becomes an adult frog.


• A frog is unisexual. There are male and female frogs.


• When the sperms fertilise the eggs in the water, we say that external fertilisation has taken place.

What other animals lay eggs which are fertilised externally?

Fishes