Echinodermata

Phylum Echinodermata (from the Greek for spiny skin) are a phylum of marine animals that includes sea stars, cucumbers, and some relatives. Groups of animals are found in almost all ocean depths. This phylum appeared in the early Cambrian period and consists of 7,000 species and 13,000 living species that are extinct. Five or six classes (six if Concentricycloidea calculated) are still alive now includes

- Starfish Asteroidea: approximately 1,500 species that capture prey for their own food
- Concentricycloidea, known for their water vascular system is unique and consists of only two species that have recently merged into Asteroidea.
- Crinoidea (sea lilies): about 600 species is a predator waiting for prey.
- Echinoids (sea urchins and sand dollars) are known for their spines are able to move; about 1,000 species.
- Holothuroidea (sea cucumbers or sea cucumber): the length of the animal resembles a snail; about 1,000 species.
- Ophiuroidea (brittle stars and serpent stars), is physically the largest echinoderms; about 1,500 species.

Forms of extinct animals that can be known from fossils including blastoids, Edrioasteriodea, Cystoidea, and several early Cambrian animals such as Helicoplacus, Carpoidea, Homalozoa, and Eocrinoidea as Gogia.

Phylum Echinodermata is the largest animal that has no members that live in fresh water or land. The animals are also easily recognizable from the shape of her body: most of them have radial symmetry, radial symmetry especially pentameral (divided into five). Although it looks primitive related phylum Echinodermata is relatively close to the Chordata (Vertebrata contained in it), and radial symmetry evolved secondarily. Starfish larvae, for example, still shows considerable similarity with Hemichordata larvae.

Many of the members who played a major role in marine ecosystems, especially coastal rocky littoral ecosystems, coral reefs, shallow waters, and ocean trenches. Species of sea star Pisaster ochraceus, for example, a major predator in the ecosystem of rocky beach on the west coast of North America, specifically, controlling the blue oyster populations (Mytilus edulis) so that other species may inhabit the coastal and mendominansi bivalves are not excessive. Another example is Acanthaster planci that eat coral polyps in the Indo-Pacific waters. Although often considered to be destructive, there are some theories that say that A. planci is actually an important predator of coral reef ecosystems, resulting in recruitment of new coral colonies which replaces the old, also reduces the pressure of competition between one species to another reef.

Echinoderms have the ability to regenerate lost body parts, such as sea cucumbers. If the sea cucumber feels threatened, it will squirt sea cucumber organs in order to get a chance to escape. Later, the missing organs will grow back