Echinodermata

The phylum Echinodermata includes animals such as starfish, sea cucumbers, sea urchans, and sand dollars. Ecdhinnoderms are marine animals which means that they live in water. Echinoderms evolved from animals with bilateral symmetry into marine animals with radial symmetry.
All echinoderms have fivefold radial symmetry
at one piont in their life. They also have an endoskeleton, inner

support system, which most invertibrates do not have.
Echinoderms have one body opening that serves as both a

mouth and anus.They have a radial nervous system,which is basically a "net"or "web" of nerves centralized around the body opening and branches our into the appendages. Echinoderms don't have a brain. Echinoderms reproduce sexually with external fertlization, they do this by releasing sperm and egg into the water and the eggs get fertilized. Some echinoderms have the ability to regenerate limbs, in the case of the starfish, it can regenerate it self from one limb so long as there is some of the body of the starfish still attached. Echinoderms have an open circulatory system. There are no blood vessels present, the blood mixes freely with other body fluids and is pumped by a series of hearts. A hydraulic water vascular system aids Echinoderms in movement, circulation and "breathing," or more accurately, gas exchange.