Fertilisation in water

The idea

In external fertilisation, seen in many aquatic animals, the female releases eggs into water and the male releases sperm over them; many eggs are laid, but many are destroyed or eaten.

A pond in the rains

A frog lays a great many eggs in a pond.

Where do you think the egg meets the sperm?

• Outside the body, in the water
• Inside the female's body
• In the air above the pond

Eggs and sperm in water

Press Next step to follow the eggs.

Outside the body

The female released the eggs and the male released sperm over them, so they met in the water. Many eggs were lost.

In external fertilisation, seen in many aquatic animals, the female releases eggs into water and the male releases sperm over them. A large number of eggs are laid, but many are destroyed or eaten.

Notes

External fertilisation: the female releases eggs into water, the male releases sperm over them. Many eggs are laid, but many are destroyed or eaten.

Check yourself

In external fertilisation, where do the egg and the sperm meet?

Which animals show external fertilisation?

What happens to many of the eggs that are laid?

What does the male do in external fertilisation?

• Inside the body of the female. That is internal fertilisation.
• Outside the body of the female, in the water — correct. Yes!
• Inside the body of the male. In external fertilisation the male releases sperm over the eggs, outside the bodies.
• Reptiles, birds and mammals. In reptiles, birds and mammals fertilisation takes place inside the body of the female.
• Plants with flowers. Flowering plants have pollination and fertilisation inside the flower.
• Frogs and most fish — correct. Yes!
• They are destroyed by water currents or eaten by other animals — correct. Yes!
• All of them become young animals. Although a large number of eggs are laid, many are destroyed or eaten.
• They are kept safe inside the mother. In external fertilisation the eggs are released into the water.
• Releases eggs into the water. The female releases the eggs.
• Releases sperm over the eggs — correct. Yes!
• Carries the fertilised egg inside his body. The eggs are released into the water and fertilised there.