Final answer:
The exoskeletons of marine arthropods are made of calcified chitin, while vertebrate endoskeletons are predominantly composed of calcified bone, allowing for greater size and strength.
Step-by-step explanation:
The exoskeletons of marine arthropods are made of calcified chitin, and the endoskeletons of vertebrates are mostly composed of calcified bone. The exoskeleton provides defense against predators, supports the body, allows for movement through muscle contractions, and is often biomineralized with calcium carbonate.
However, the exoskeleton does not grow with the organism, limiting its size and requiring molting for growth. On the other hand, the vertebrate endoskeleton, made of bone or cartilage, allows for larger size due to its strength and the fact that muscles are attached on the outside, providing more leverage and efficiency in handling increased mass.