skeletal material
skeletal material In most vertebrates the skeleton is made from bone (calcium phosphate); among invertebrates it is more varied. Calcite or aragonite in various forms is common in such groups as the brachiopods (Brachiopoda) and molluscs (Mollusca). Normally the invertebrate skeleton is made up from several layers, and often each layer has a distinctive structure. The main, calcified portion of the shell is called the ‘ostracum’; an outer layer, the ‘periostracum’ (made from layers of protein), disappears after death. Calcitic skeletons also occur in corals and Bryozoa. Echinoderms (Echinodermata) have skeletons made up of a number of elements. Each element is permeated with living tissue but the hard material is calcite, which forms in optical continuity to form a single crystal. Chitin (a hydrocarbon related to cellulose) is the principal component of insect cuticle. It has been assumed that chitin impregnated with calcium carbonate forms the exoskeletal material in trilobites (Trilobita), but although organic material occurs its nature is still unknown. Similarly, recent studies of graptolite (Graptolithina) skeletal material have shown that the material is not chitin but a scleroprotein (a fibrous, insoluble protein). In some simple animals, e.g. Radiolaria and some sponges (Porifera), the skeleton is composed of opaline silica.
More From encyclopedia.com
material , ma·te·ri·al / məˈti(ə)rēəl/ • n. 1. the matter from which a thing is or can be made: goats can eat more or less any plant material | materials such a… Materialism , Materialism is a term with both metaphysical and social meanings. As a metaphysical position materialism regards matter (Latin materia) as the primar… Biomineralization , biomineralization The incorporation of inorganic compounds, such as salts, into biological structures, often to lend them hardness or rigidity. Biomi… Magnet , Magnet
Background
A magnet is a material that can exert a noticeable force on other materials without actually contacting them. This force is known a… Compost , Compost
Compost is a finely divided, loose material consisting of decomposed organic matter. It is primarily used as a plant nutrient and soil condit… Asthenosphere , The asthenosphere is the layer of Earth situated at an average depth of about 62 mi (about 100 km) beneath Earth's surface. It was first named in 191…
You Might Also Like
NEARBY TERMS
skeletal material