You are here
💡 Inside or outside?
A frog scatters its eggs into a pond; a bird keeps its egg safe inside first. Where the gametes meet changes everything about how many young survive.
What are external and internal fertilisation?
Fertilisation in Animals
External — Internal — inside gametes meet in the female body; water; many eggs, fewer eggs, higher low survival (fish, survival (birds, frogs) mammals)
- In external fertilisation , the female releases eggs into water and the male releases sperm over them (frogs, most fish); many eggs are laid but many are lost.
- In internal fertilisation , fertilisation takes place inside the female’s body (reptiles, birds, mammals).
- Survival of young ones is generally higher in internal fertilisation because the fertilised egg or embryo is better protected.
Important Definitions
- External fertilisation — fusion of gametes outside the body, usually in water, as in frogs and most fish.
- Internal fertilisation — fusion of gametes inside the female’s body, as in reptiles, birds and mammals.
