In the animal kingdom, different species have unique characteristics and tactics for survival. Some animals in particular rely on their shells.
Animals depend on their shells for a variety of reasons. Most shells function as homes for animals. Shells also help give an animal shape and protect the softer parts of its body. Finally, shells prevent animals from drying out while they are on land.
The most common shelled species is the mollusk. The mollusk takes chalky matter in the water around it and deposits it into layers. Eventually, these layers form a strong, thick shell.
Mollusks are bivalves, meaning they have a two-part shell. The two halves of the shell are held together with strong muscles and a hinge. This allows bivalves to open their shells while feeding but close them when threatened. Once they smack the halves of their shells together, bivalves can quickly swim away from predators and to safety.
Some mollusks, including chitons, have unusual shells that are flat instead of round. These shells consist of eight overlapping plates, or valves, that are connected with hinges. The chiton’s hinges allow it to bend as it moves over rocks.
Other aquatic species use their shells differently, like the cuttlefish for example. Its shell serves as a gas-filled flotation device. The cuttlefish is able to change the amount of gas inside of its shell as it floats, which lets it rise to the water’s surface at times and sink to the water’s bed at other times.
It’s clear that shells are useful in a variety of ways, each of which is important for the shell owner’s survival!
[Source: How Animals Work]