Write the general characteristics of the phylum Echinodermata.

(N/A) $\rightarrow$ Echinoderms possess an endoskeleton of calcareous ossicles,hence the name Echinodermata (spiny-bodied).
$\rightarrow$ All are marine with an organ-system level of organization.
$\rightarrow$ Adult echinoderms are radially symmetrical,whereas larvae are bilaterally symmetrical.
$\rightarrow$ They are triploblastic and coelomate animals.
$\rightarrow$ The digestive system is complete,with the mouth on the lower (ventral) side and the anus on the upper (dorsal) side.
$\rightarrow$ The most distinctive feature of echinoderms is the presence of a water vascular system,which aids in locomotion,capture and transport of food,and respiration.
$\rightarrow$ An excretory system is absent.
$\rightarrow$ Sexes are separate (dioecious).
$\rightarrow$ Reproduction is sexual.
$\rightarrow$ Fertilization is usually external.
$\rightarrow$ Development is indirect,involving a free-swimming larva.
$\rightarrow$ Examples: Asterias (starfish),Echinus (sea urchin),Antedon (sea lily),Cucumaria (sea cucumber),and Ophiura (brittle star).