Asteroids-carnivory
Keystone predators
Pisaster ochraeus
Echinoids-herbivory
Stonglyocentrotus drobachiensis
uses a structure called aristotle's lantern to scrape algae off the substrate
Filter feeding
Brittle star--basket star

deposit feeding-
holothuroid--beche de mer, sea cucumbers

Nervous systems

depends upon events taking place at the cell level
membranes have a membrane potential