Mammals（哺乳类动物） are covered by hair or fur（毛皮）,have a backbone（脊椎） and are warm-blooded（温血的）.

All female（雌性） mammals（哺乳动物） produce milk for their young.

Reptiles（爬行动物） are covered by scales（鳞片） and include snakes,lizards（蜥蜴） and turtles（乌龟）.

Reptiles have a backbone and are cold-blooded,which means they often rely on（依靠） external（外部的） sources of heat（热度）.

Birds are covered by feathers and are warm-blooded.

Most birds can fly and many types of birds migrate（迁徙） great distances.

Most insects such as ants and bees have a small,3-part body with 3 pairs of legs.

Some insects,like mosquitoes（蚊子）,spread（传播） diseases（疾病） that cause the deaths of many humans.

Unlike animals,plants get the energy that they need from the sun.

Plants convert light energy,along with carbon-dioxide（二氧化碳） and water,into chemical energy.

Mosquitoes cause the deaths of more humans than any other animal.

Insects such as ants and bees live in well-organized（组织有序） colonies（聚居地）.

Most mammals live on land,but some live in the sea.