1001 Space Earth Nature Evolution Fossils and Prehistoric Life Dinosaurs Simple Animals Insects and Spiders Fish Amphibians Reptiles Birds Sea Mammals Land Mammals Plant Kingdom How Plants Live Unusual Plants Ecology Conservation Animal Behaviour Pets and Farm Animals History Human World Science and Technology

What use is a skeleton? An animal that lives on land needs a skeleton to support it and to help it move. Some animals, including humans, have a skeleton on the inside. Some animals, like insects and spiders, have a hard skeleton on the outside. Many simple animals that float in the sea, like the jellyfish, do not have a skeleton at all. They do not need one because the water they float in gives them all the support they need. The umbrella-shaped jellyfish swims by rhythmically contracting its body.   Previous: Back Book: 1001 Section: Nature Chapter: Simple Animals