Do sharks have skeletons like people do?

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Do sharks have skeletons like people do?

You'd think so, but they don't, really. While many types of fish have skeletons made of bone very similar to our own skeletons -- made of calcium and other hard minerals -- sharks don't. Most of a shark's "skeleton" is actually made of cartilage, a soft, flexible material. Cartilage is the material used in our own noses, for example. Having a "skeleton" made of cartilage makes sharks more flexible and maneuverable, which helps them catch their prey.

There is some calcium in a shark's cartilage to make it stronger, but it's still pretty flexible. The highest amount of calcium is found in a shark's jaws and teeth. There the strength approaches the strength of what we normally think of as bone. That's why you'll often find that the most common "remains" of a shark that's sold in stores is the jawbone and its attached teeth. It's often all that is hard enough to survive, after a shark dies.

By the way, sharks don't have to worry about tooth decay. They continue growing new teeth -- and losing their old ones -- as they grow older. As the old teeth wear and age, new rows grow behind them and move forward in the shark's mouth, replacing the old teeth as they fall out. Sometimes a row of teeth will be replaced as often as every two weeks, usually in the most active feeding seasons. At other times and for different species of shark it can take months for that to happen.

Because their skeletons are made of flexible cartilage, even small sharks can open their mouths surprisingly wide. Even small sharks can swallow pretty large fish when they get a chance.

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