Page 24 - 新思维科学学生用书4 样章

1.4 Different kinds of skeletons

• 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 locust

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 jellyfish

not have an exoskeleton.

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