As an expert in the field of biology, I can provide you with a detailed explanation of what an exoskeleton is and which animals possess this type of protective covering. An exoskeleton is a hard, external covering that supports and protects an animal's body. It is made up of a material called chitin, which is a complex carbohydrate, and proteins. This structure is particularly common among invertebrates, which are animals without a backbone.

Insects are a prime example of animals with exoskeletons. This group includes a vast array of creatures such as grasshoppers, cockroaches, bees, butterflies, and ants. The exoskeleton in insects serves multiple purposes. It provides structural support, allowing the insect to maintain its shape and move efficiently. It also offers protection from predators and physical damage. Additionally, the exoskeleton helps to reduce water loss, which is crucial for insects living in dry environments.

Crustaceans, such as crabs, lobsters, and shrimp, also have exoskeletons. These aquatic animals use their exoskeletons for protection and support. The hard shell of a crustacean's exoskeleton is composed of calcium carbonate and proteins, which gives it a unique strength and flexibility. Crustaceans must molt, or shed their exoskeleton, to grow, as their exoskeleton does not expand with their body.

The shells of certain sponges are considered exoskeletons. Sponges are simple, multicellular organisms that are part of the phylum Porifera. While not all sponges have a hard shell, those that do, like the sphingids, use their exoskeleton for support and protection.

The mollusks are a diverse group of invertebrates that include animals like snails, clams, tusk shells, chitons, and the nautilus. Many mollusks have an exoskeleton in the form of a shell. The shell is made up of layers of a material called nacre, also known as mother-of-pearl, which is secreted by the mollusk over time. This shell provides protection and support, and in some species, it can be coiled into a spiral shape.

Myriapods, which include centipedes and millipedes, are another group of animals that have an exoskeleton. Their exoskeleton is composed of chitin and serves to protect the animal and provide structural support. Myriapods have a segmented body, and each segment is covered by a ring of the exoskeleton.

Trilobites, now extinct, were a group of marine arthropods that lived in the Paleozoic Era. They had a well-developed exoskeleton that was divided into three main parts: the head, the thorax, and the tail. The trilobite's exoskeleton was made of chitin and provided protection from predators and the environment.

In addition to these, there are other less well-known animals with exoskeletons, such as tardigrades (also known as water bears), which are tiny, eight-legged micro-animals that can survive extreme conditions. Their exoskeletons are composed of a protein called tardigrade-specific protein, which is different from chitin.

In summary, exoskeletons are a common feature among many invertebrates, providing them with structural support, protection, and in some cases, aiding in their ability to conserve water. The composition and structure of exoskeletons can vary widely among different animal groups, reflecting the diverse evolutionary solutions to the challenges of living in various environments.

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Examples of animals with exoskeletons include insects such as grasshoppers and cockroaches, and crustaceans such as crabs and lobsters. The shells of certain sponges and the various groups of shelled molluscs, including those of snails, clams, tusk shells, chitons and nautilus, are also exoskeletons.read more >>