Sea urchins are closely related to starfish. Both animals are members of a group known as echinoderms. The purple sea urchin is found off the west coast of North America from Canada to Baja California. They are common in the kelp forests of California where they feed on the kelp and other algae. Their sharp spines help protect them from would-be predators. Some species of urchins are venomous and can deliver a toxic sting through their sharp spines.