I am sure that many of you, if not all of you, have been to the tide pools sometime in your lives. They are marine invertebrate animals of the phylum Echinodermata. This is because of their external skeleton of calcareous plates just under the skin, no head. They ha ve unique water-vascular systems with tube feet. Echinoderms are radially symmetrical, they lack specialized excretory organs, and reproduce sexually.
Echinoderms have extensive powers of regeneration of lost or injured parts.
All of the members live on the sea floor. Other members of this class include, seastars, brittle stars, sand dollars, sea cucumbers, and crinoids. There are many types of sea urchins. Green, red, rock-boring, heart, purple, and more. But for this research I am basing most of my information on the purple sea urchin, found along the Pacific Coast.