One advantage an exoskeleton provides is a strong outer layer that acts as armor against predators and environmental hazards. It also serves as a protective water barrier, and it imparts advantages related to structure and mobility.
Like endoskeletons, exoskeletons provide structure and support to an animal's body. However, exoskeletons encase all of an animal's living tissues, protecting them from damage and attack. Muscles used for locomotion attach directly to the exoskeleton, giving the animal better leverage for rapid movement.
One of the most important functions of an exoskeleton is to prevent land-dwelling species from drying out. This is crucial because of the vital role played by water in physiological processes. On the other hand, an exoskeleton protects ocean-dwelling animals from being affected by small changes in the saltiness of water in their environment.
While some exoskeletons are dense, such as the hard shells of clams, the exoskeletons of insects are lightweight, making it possible for them to fly. Being nonliving, an exoskeleton does not grow with an animal. Therefore, it must be periodically shed in a process called molting. A new exoskeleton is then formed from epidermal secretions. This process consumes metabolic resources, and the animal is vulnerable until the new exoskeleton hardens.