What is meant by the terms 'internal fertilisation' and 'external fertilisation' ? Explain with examples

Internal Fertilisation

• Definition: Fertilisation that takes place inside the female body.
• Process: The male deposits sperms into the female reproductive tract, where they fuse with eggs.
• Examples: Humans, cows, dogs, birds, and reptiles.
• Advantage: The developing zygote is protected inside the female body.

External Fertilisation

• Definition: Fertilisation that occurs outside the female body, usually in water.
• Process: Both male and female release gametes into the surrounding medium (mostly water), where fusion happens.
• Examples: Frogs, fish, and amphibians.
• Advantage: A large number of gametes are produced, increasing chances of fertilisation.

In short: Internal fertilisation = inside the body (humans, birds); External fertilisation = outside the body, in water (frogs, fish).