Characterized by radial symmetry Several arms radiating from a central body body consists of five equal segments, each containing a duplicate set of various internal organs no heart, brain, or eyes mouth is situated on the underside and their anus on top do not possess an external skeleton. a thin outermost skin covers a mesodermal endoskeleton made of tiny calcified plates and spines
Echinoderms are exclusively marine Occur in various habitats intertidal zones, the bottom of the deep sea trenches, coral reefs, cold and tropical seas Some are carnivorous, others are detritus foragers, or planktonic feeders Reproduction is carried out by the release of sperm and eggs into the water Most species produce pelagic (free floating) planktonic larvae which feed on plankton
Echinoderms are important both biologically and geologically few other groupings are so abundant in the biotic desert of the deep sea, as well as the shallower oceans their ossified skeletons are major contributors to many limestone formations, and can provide valuable clues as to the geological environment.
Sea Stars typically have five "arms" which radiate from a central disk usually hunt for shelled animals such as oysters and clams have two stomachs, one for digestion, and one can be extended outward to engulf and digest prey radiate diversely in shapes and colors
Sea Cucumbers elongated body and leathery skin Generally scavengers, feeding on debris Communicate through sending hormone signals through the water body wall can be loosened and tightened at will If it wants to squeeze through a small gap it can essentially liquefy its body and pour into the space.
Sea Urchins small, spiny, globular creatures move slowly, feeding mostly on algae light touch elicits a prompt and visible reaction from the spines, which converge toward the point that has been touched
Sand Dollars have a skin of moveable spines when it is found washed up on the beach, it is dead has a set of five paired rows of pores that are arranged in a petal-like pattern
Crinoids Also known as sea lilies or feather-stars a mouth on the top surface that is surrounded by feeding arms usually have a stem used to attach themselves to a substrate, but many live attached only as juveniles and become free-swimming as adults