| A | B |
|---|
| Mantle | thin layer of tissue that secretes a mollusk's shell |
| echinoderm | spiny-skinned invertebrate that lives on the ocean floor |
| open-circulatory system | blood is not in vessels but surrounds organs |
| medusa | bell-shaped body plan, like that of a jellyfish |
| arthropod | jointed-foot animal |
| gills | organs that exchange oxygen and carbon dioxide with water |
| radula | tongue-like organ in mollusks that works like a file |
| bilateral | type of symmetry in which body parts are mirror images of each other |
