Vertebrates

Vertebrates are animals with backbones. They can be classified according to their features, and include bony fish, amphibians, reptiles, birds and mammals.

Bony fish

Bony fish absorb oxygen through their gills and they have wet scales. Their body temperature varies according to their surroundings (organisms that do this are called poikilotherms). Bony fish reproduce by external fertilisation and lay eggs (they are oviparous).

Shoal of clown fish
Clownfish are bony fish

Amphibians

Amphibians usually have lungs but they can also absorb oxygen through their moist skin. Their body temperature also varies according to their surroundings. Amphibians also reproduce by external fertilisation and lay eggs.

Red-eyed tree frog
Frogs are amphibians

Reptiles

Reptiles have lungs and dry scales. As with bony fish and amphibians, their body temperature varies according to their surroundings. However, reptiles reproduce by internal fertilisation and lay eggs.

Python coiled up in to a perfect circle
Snakes are reptiles

Birds

Birds have lungs, feathers and beaks. They can maintain their body temperature (organisms that do this are called homeotherms). Like reptiles, birds reproduce by internal fertilisation and lay eggs.

Goldfinch perched on a wire frence
Goldfinches are birds

Mammals

Mammals have lungs and fur. Like birds, they can maintain their body temperature. Mammals reproduce by internal fertilisation and they give birth to live young (they are viviparous).

Grey squirrel eating nuts
Squirrels are mammals