| A | B |
|---|
| Mollusk | An invertebrate with a soft, unsegmented body; most are protected by hard outer shells |
| Kidney | A major organ of the excretory system; eliminates urea, excess water and the other waste materials from the body |
| Gill | An organism's breathing organ that removes oxygen from water |
| Radula | A flexible ribbon of tiny teeth in mollusks |
| Gastropod | A mollusk with a single shell or no shell |
| Bivalve | A mollusk that has two shells held together by hinges and strong muscles |
| Cephalopod | Amollusk with feet adapted to form tentacles around its mouth |
| Anthropod | An invertebrate that has an external skeleton, a segmented body, and jointed attachments called appendages |
| Exoskeleton | An outer skeleton |
| Chitin | The tough, flexible, material from which arthropod exoskeletons are made |
| Molting | The process of shedding an outgrown exoskeleton |
| Antenna | An appendage on the head of some animals that contains sense organs |
| Crustacean | An anthropod that has two or three body sections, five or more pairs of legs, two pairs of antennae and ususally three pairs of appendages for chewing |
| Metamorphosis | A process in which an animal's body undergoes dramatic changes in form during its life cycle |
| Arachnid | An arthropod with only two body sections |
| Abdomen | The hind section of an arachnid's body that contains its reproductive organs and part of its digestive tract; the hind section of an insect's body |
| Insect | An arthropod with three body sections, six legs, one pair of antennae and usually one or two pairs of wings |
| Thorax | An insect's mid-section, to which its wings and legs are attached |
| Complete metamorphosis | A type of metamorphosis characterized by four dramatically different stages:egg, larva, pupa, and adult |
| Pupa | The second stage of the complete metamorphosis, in which an insect is enclosed in a protective covering and gradually changes from a larva to an adult |
| Gradual metamorphosis | A type of metamorphosis in which an egg hatches into a nymph that resembles an adult, and which has no distinctly different larval stage |
| Nymph | Astage of gradual metamorphosis that usually resembles the adult insect |
| Camouflage | Protective coloration; a common animal defense |
| Pheromone | A chemical released by one animal that affects the behavior of another animal of the same species |
| Bioluminescence | The production of light by a living organism |
| Echinoderm | A radially symmetrical invertebrate that lives on the ocean floor and has a spiny internal skeleton |
| Endoskeleton | An internal skeleton |
| Water vascular system | Asystem of fluid-filled tubes in an echinoderm's body |
