2.- From zygote to birth

Animals that are born from an egg are called oviparous animals. In these animals, the zygote develops into an embryo inside the egg.

The egg forms a protective shell around the zygote cell. It also contains the food that the zygote needs to develop into an embryo.

Some eggs are small and very simple. The eggs of fish and amphibians, for example, are made up of an embryo and soft, gelatine shell.

Other eggs are larger and more complex.

The eggs of reptiles and birds are made up of a yolk,

eggs white and a hard shell.

Oviparous animals

After fertilisation, the zygote starts to divide and grow into an embryo. The embryo develops until it is ready to survive externally, and then it is born.