Echinoderms are marine animals with radial or pentaradial symmetry and include sea stars, sea urchins, sand dollars, brittle stars, and sea cucumbers. They have a water vascular system and tube feet for movement and respiration. Their endoskeleton is covered by skin and spines. Sea stars have five arms from a central disk and feed on bivalves and snails. Sea urchins have movable spines and plates and feed on algae using specialized jaws. Sea cucumbers have tube feet in rows and some can expel their internal organs as a defense mechanism.

1. Phylum Echinodermata Kingdom Animalia Phylum Echinodermata Class Asteroidea Class Ophiuroidea Class Echinoidea Class Holothuroidea

7. Water Vascular System: