> Which of the following ocean creatures has an exoskeleton?And the answer: snow crabs. Photo Courtesy: The Fish Site.An exoskeleton is the external skeleton thatsupports and protects an animal's body. It's different from an endoskeleton, thetype that humans have, which supports from the inside. Animals with exoskeletonsinclude insects such as grasshoppers and ants, and crustaceans like crabs andlobsters.Exoskeletons are excellent forms of defense for smaller animals such asarthropods (insects and spiders) and crustaceans (lobsters, shrimp, snails andcrabs). Most have several segments, each one with a somewhat separate piece ofan exoskeleton, so the animal's head and body parts can move separately. Thedefense is extremely effective – it helps to support the animal's body whilefunctioning somewhat like a portable raincoat that prevents the creature fromgetting wet or drying out.You may be wondering: why are humans stuck with measly bones if creatures withexoskeletons get a shield and system of support all at once? Well, for that wemust look to gravity: an equivalent external skeleton on a larger creature wouldbe extremely heavy. So heavy that we would barely be able to move or function.Instead, our marrow-filled, light, regenerable bones keep us mobile whileholding us together – and get it all done from the inside. Exoskeletons are generally composed of chitin (a complex polysaccharide that ischemically similar to cellulose) and calcium carbonate (common in rocks andeggshells). As animals with exoskeletons age, their soft inside parts grow buttheir firm exoskeletons do not. When an animal’s body gets too big for theexoskeleton, it splits open and falls away in a process called molting.Consequently, the animal’s body forms a new exoskeleton. To learn more about the bones supporting the life on Earth (inside and out),check out the video below.