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Dinosaurs have been extinct for millions of years. However, archeologists have been able to learn a lot about dinosaurs from the bones they have found. Using computers, it's possible to determine how a prehistoric animal moved by examining its skeleton. We can learn a lot from a skeleton because it's vital to the structure and movement of the animal.

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A skeleton has three roles. It provides support for an animal's body. Without the framework of your skeleton, you'd sag from the weight of your body and become a formless mass. A skeleton also provides protection for an animal's soft tissues. Our ribs protect our heart, lungs, and other organs from being damaged during everyday activities. A skeleton is also important for movement. It gives the muscles a solid structure to work against.

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When we think of a skeleton, we usually think of a bunch of bones. But bones make up just one type of skeleton. A grasshopper has a skeleton that isn't made of bones. A grasshopper's skeleton is the hard covering on the outside of its body. And you might not realize it, but an earthworm has a skeleton too. An earthworm's skeleton is composed of fluid held under pressure in a closed compartment. The earthworm's muscles can change the shape of the compartment to allow the worm to move.

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In this activity, we'll look at the three different types of skeletons. We'll start by exploring hydrostatic skeletons, which are composed of fluid under pressure, and exoskeletons, found on the outside of certain animals. Then we'll look at endoskeletons, which are found inside certain organisms.

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