Echinoderms and divergent development

With their variety of shapes they are a prime example of divergent development. The concept of divergence can be defined as the development of closely related organisms in different directions due to different adjustments to their habitat and/or lifestyle. Therefore every organism occupies a certain ecological niche. Furthermore they inhabit a majority of the marine habitats from sandy and soft bottoms to the hard bottom structures of the Sublittoral. Echinoderms are an exclusively marine class, occuring in various habitats from the intertidal zone down to the bottom of the deep sea trenches. From sand bottom to coral reefs, in cold and tropical seas. For reproduction, sperm and eggs are released into the water. Most echinoderm species produce pelagic planktonic larvae which feed on plankton. Unlike their parents, these larvae are bilaterally symmetrical. After their settlement to the bottom they change to the typical echinoderm features.