Biological system: Difference between revisions

The '''skeletal system''' provides support and protection for [[animals]]. There are two main types of skeletal systems. The endoskeleton is an interal support system of the type possessed by [[humans]] and other [[vertebrates]], which is made of bone. The exoskeleton is an external system that was designed for many invertebrates such as the [[crustaceans]] and [[insects]]. The composition of exoskeletons vary widely, but known constituents include [[calcium]] [[salts]], [[protein]], [[carbohydrates]] ([[chitin]]) and silicate.