| A | B |
|---|
| symmetry | arrangement of individual body parts |
| invertebrate | an animal without a backbone |
| cnidarian | radially symmetrical, hollow-bodied animals with two cell layers organized into tissues |
| polyp | vase shaped, usually sessile body form in the life cycle of a cnidarian |
| mollusk | soft-bodied, bilaterally symmetrical invertebrate with a large, muscular foot, a mantle, and an open circulatory system |
| mantle | thin layer of tissue that covers a mollusk's body and that can secrete a shell |
| gill | organ that allows a water-dwelling animal to exchange carbon dioxide for dissolved oxygen in the water |
| radula | scratchy, tonguelike organ in many mollusks that has rows of teethlike projections used to scrape and grate food |
| open circulatory system | a type of blood-circulation system that lacks bolld vessels and in which blood washes over the organs |
| closed circulatory system | a type of blood-circulation system in which blood is transported through blood vessels rather than surrounding the organs |
| arthropod | bilaterally symmetrical animal with jointed appendages, a protective exoskeleton, and a segmented body |
| appendage | structure such as a claw, leg, or antenna that grows from the body |
| exoskeleton | rigid, protective body covering of an arthropod that supports the body and reduces water loss |
| metamorphosis | change of body form that can be complete or incomplete |
| medusa | free-swimming, bell-shaped body form in the life cycle of a cnidarian |
