Echinoderms are defined as any of a variety of invertebrate marine animals characterized by a hard, spiny covering or skin. They have attracted much attention due to their extensive fossil record, ecological importance, and bizarre body forms. Most echinoderms are extinct, but many living representatives still exist. All living echinoderms have an internal skeleton and a central cavity, but the outward appearance can vary significantly. For example, starfish and brittle stars have arms that extend from a central disk; sea lilies have a central stalk, or stem, and resemble flowers; sea cucumbers are wormlike and tend to burrow. The ways in which echinoderms move and feed are as diverse as their body forms. Table 1 lists certain echinoderms and their methods of locomotion (movement) and feeding Table 2 includes examples of echinoderms habitats around the world. The echinoderm shown below is most likely a:

Correct answer: C. Sea cucumber

• A. Sea lily
• B. Starfish
• C. Sea cucumber
• D. Brittle star

Last updated 3 September 2026