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Characteristics of the Five Vertebrate Groups


Fish, Bristol Zoo, UK © Shirley Burchill

The body of the fish is covered in scales and has fins attached to help it move through the water. Fish breathe using gills which take oxygen out of the water. When male and female fish mate, the eggs often meet the sperm in the water. This is called external fertilization. Examples of fish are the herring, which lives in the sea, and the pike which is a freshwater fish.


Frog © Paul Billiet

The skin of amphibians is very thin and must always be kept wet because amphibians breathe through their skin. The do have lungs, but their lungs are small and are not used very much. Fertilization of the eggs is external, taking place in the water. The eggs are covered with jelly to protect them. The larvae, called tadpoles, are aquatic. They slowly change (metamorphose) into the adult amphibian which lives on land but always near water. Examples of amphibians are the frog and the newt.


Lizard, Kenya © Shirley Burchill

The body of a reptile is covered in hard scales. Reptiles live on land, although many of them swim well and may feed in water, such as some snakes and lizards. They breathe using lungs. When male and female mate fertilization is internal. The female lays soft-shelled eggs which are often buried in sand or in the earth to protect them while the young develop inside. Examples of reptiles are crocodiles, snakes and lizards.


Hawk, Devon, UK © Shirley Burchill

Birds have bodies covered with feathers. They do not have teeth but use their beaks to eat their food. Their front limbs are adapted as wings, although not all birds fly. Birds breathe using lungs. Fertilization is internal and the females lay eggs with hard shells, usually in a nest. Most birds incubate their eggs until the eggs hatch. Examples of birds are the stork, the eagle and the penguin.

Johnny's Fact File No.4
Facts iconThere are nearly 9000 different types of birds in the world. One of the largest birds is a sea-bird called the albatross. It has a wingspan of 3,5 metres.


All mammals have a body covering of either hair or fur. They breathe using lungs.

Asian lion, Bristol Zoo, UK © Shirley Burchill

Fertilization is internal and the females feed their young with milk from their mammary glands. Most mammals are viviparous. This means that the offspring are kept inside the female's body and feed through a placenta. The largest mammal lives in the sea. It is the blue whale, which can reach 33,6 metres in length and has a mass of 190 tonnes. The smallest mammal is called the bumble bee bat. This tiny bat lives in Thailand. It has a mass of just under 2 grammes and a wingspan of 16 cm.

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