Why do some animals have shells?

Shells are a common feature of many animals, from mollusks to turtles. These shells serve a variety of purposes, including protection, support, and camouflage.

One of the primary reasons that animals have shells is for protection. For example, turtles have a hard, bony shell that protects them from predators, while snails and clams have shells that protect their soft bodies from harm. Some animals, like crabs, have shells that provide protection during the vulnerable molting process.

Shells can also serve as a form of support. For example, the shells of cephalopods like nautiluses and ammonites are filled with gas, allowing them to float in the water column without expending much energy. Similarly, the shells of some sea urchins and starfish provide support for their tube feet and spines.

Finally, shells can also serve as a form of camouflage. Many animals, like hermit crabs, use shells from other creatures as a protective covering that also helps them blend in with their surroundings.

Overall, shells are a remarkable example of how animals have adapted to their environments over time through evolution.