Skeletal System of Arthropoda
One main commonality among the species in the phylum Arthropoda are the exoskeleton and segmented body that they all possess. The exoskeletons are made of cuticle, a non-cellular molecule that is secreted by the epidermis. The exoskeleton of arthropods can not stretch, which causes arthropods to go through a process called moulting, where they shed their exoskeleton and start making a new once once they have outgrown it. This outgrown exoskeleton can then be eaten by the organism to gain the nutrients needed to form a new, larger exoskeleton. This phylum has shown evolution as each of these animals molt, or shed their shell, to allow for more extensive growth, which can be used as an advantage over the other occupants of their ecosystems.