Echinodermata
This is a phylum of marine animals. Adults of the echinoderms are easily recognizable by the pointed radial symmetry. This includes animals such as sea stars, sea urchins, and sand dollars. They are usually found in ocean depths from the intertidal zone to the abyssal zone. This phylum contains an estimate of seventy thousand living species. This makes it one of the largest groups of deuterstomes. This is the largest phylum that has no freshwater representatives. This phylum dates back to the start of the Cambrian period.
General Information
The echinoderms do not have a circulatory system. Yet the circulatory system is important for us, the echinoderms have a water vascular system. This is their system to survive in the depths of ocean to maintain homeostasis. This is called the ambulacral system. This system is a network in which there are fluid- filled canals that helps in gas exchange, feeding, and secondarily in locomotion. This system allows for the starfish to live without having gill slits. This system uses a central ring, the hydrocoel, the radial ambulacra stretching throughout the body and arms. This system also gathers nutrients for the body. There are crinoids that allow for the particles of food to be sucked up. Animals such as sea urchins also gathers food by turning their body in the way that their mouth is able to catch wandering prey.