Starfish

Objective: On your blog, describe a starfish in terms of symmetry, germ cell layers, coelem, Circulatory system, reproduction, feeding, excretion and nervous system. Find picture examples of each living class Crinoidea, Ophiocistioidea, Astroidea, Echinoiudea and Holothuidea.

Starfish have a radial symmetry because of their five arms. Their exoskeleton are composed of a double  cell layered. Their coelem have an open circulatory system because they are water vascular. Water flow through their mouth and through all five of it's arms. Starfish keep their eggs in their arms and fertilize them externally. Starfish can also reproduce asexually from broken limbs. They prey open mollusks, eat vegetation, and debris. They lack excretory systems so they release their waste through pores on their skins. They have a circum-oesophageal ring that acts as their nervous system.

Crinoidea -1st picture, sea fan
Ophiocistioidea-4th picture, 6+ armed starfish
 Astroidea-3rd picture, regular 5 armed starfish
 Echinoiudea-2nd picture, Sea Urchin
 Holothuidea-5th picture, Sea Cucumber