| A | B |
|---|
| mollusks | invertebrates with soft, unsegmented bodies, that are often protected by hard outer shells |
| mantle | thin layer of tissue that helps produce a mollusk's shell |
| kidneys | organs that remove waste |
| gills | organs that remove oxygen from water |
| radula | a flexible ribbon of tiny teeth |
| three major groups of mollusks | gastropods, bivalves, and cephalopods |
| gastropods | mollusts have a single shell or no shell |
| bivalves | mollusks that have two shells held together by hinges and strong muscles |
| cephalopods | mollusks whose feet are adapted to form tentacles |
| arthropod | invertebrate that has an external skeleton, a segmented body, and jointed attachments called appendages |
| exoskeleton | outside skeleton |
| endoskeleton | internal skeleton |
| chitin | tough and flexible outer shell of artropods are made from this |
| antenna | an appendage on the head that contains some sense organs |
| three major groups of arthropods | crustaceans, arachnids, and insects |
| crustacean | arthropod that has two or three body sections and usually has three pairs of appendages for chewing |
| metamporphosis | a process in which an animal's body undergoes dramatic changes in form during its life cycle |
| molting | the process of shedding an outgrown exoskeleton |
| arachnid | arthropod with only two body sections and no antennas |
| abdomen | the hind section of an arthropod |
| insects | arthropods with three sections, six legs, one pair of antenna and usuall one or two pairs of wings |
| thorax | mid-section of an arthropod |
| complete metamorphosis | egg, larva, pupa, and adult stages |
| pupa | the insect is enclosed in a protective covering during the second stage of metamorphosis |
| gradual metamorphosis | an egg hatches into a nymph |
| nymph | a miniature adult insect |
| camoflage | protective coloration |
| echinoderms | a radially symmetrical invertebrate that lives on the ocean floor |
| water vascular system | fluid-filled tubes within the echinoderm's body |
