Animals with bones

The animals in the pictures all have bones. They have a skeleton with a backbone inside their bodies. We call animals with skeletons inside their bodies vertebrates. The word vertebrate means ‘with a backbone’.

We can sort vertebrates into five groups. See if you can identify the group that each of the animals in the pictures belongs to.

• Fish are vertebrates that live in water. They have fins instead of arms and legs. Their bodies are covered with scales.
• Amphibians, such as frogs, live in water and on land. Their bodies are covered with a smooth, wet skin.
• Reptiles, such as snakes, lizards and tortoises, are covered with dry scales. Most reptiles live on land. Some reptiles live in water, for example crocodiles.
• Birds are covered with feathers. Birds have wings instead of arms. Most birds can fly. Some birds, like the ostrich, cannot fly.
• Mammals are covered with hair or fur. Most mammals live on land. Some mammals live in the sea, for example whales and dolphins.

Animals without bones

Some animals have no bones. Animals with no bones are called invertebrates. The word invertebrate means ‘without a backbone’.

Some invertebrate animals have hard skins or shells on the outside of their bodies. This hard outer layer is called an exoskeleton. The exoskeleton protects the animal and supports the animal’s body. Insects, such as locusts and beetles, have an exoskeleton.

Other invertebrate animals such as worms and jellyfish have soft bodies. These animals do not have an exoskeleton.

Identification keys

Scientists use identification keys to help them sort and identify objects, materials and living things. Identification keys are based on questions that can be answered either ‘yes’ or ‘no’. By answering the questions, we can identify and name animals, or sort them into the right groups.

Look at this example which identifies different types of vertebrates.