Eggs or live young?
Find out how twelve animals, from the hen and the frog to the cow and the whale, have their young and where fertilisation happens, then sort them into egg-layers and those that give birth.
Core concept
Oviparous animals lay eggs and viviparous animals give birth to young; fertilisation happens inside the female (internal) or outside in water (external)
Topic: Reproduction in animals
In sexual reproduction a male gamete (sperm) joins a female gamete (egg) in fertilisation, making a zygote that grows into a new animal. Animals do this in two ways. In internal fertilisation the egg and sperm meet inside the female's body, as in hens, snakes, cows and humans. In external fertilisation they meet outside, usually in water, as in frogs and most fish, which lay huge numbers of eggs. After fertilisation, oviparous animals lay eggs and the young hatch outside, while viviparous animals keep the young inside the mother until birth.
What you will learn
- Tell oviparous from viviparous animals.
- Explain internal and external fertilisation.
- Explain why frogs and fish lay so many eggs.
Before you start
- Know that animals grow from young ones.
Materials
- Pictures of animals and their young, or frog spawn in a pond (just look)
Equipment
- A hand lens
Procedure
- Pick a card and find how the young are born and where fertilisation happens.
- Do this for at least eight animals.
- Sort every animal into oviparous or viviparous.