| A | B |
|---|
| organ | A structure in the body that is composed of different kinds of tissue |
| adaptation | A characteristic that helps an organism survive in its environment or reproduce |
| herbivore | An animal that eats only plants |
| carnivore | An animal that eats only other animals |
| predator | A carnivore that hunts and kills other animals for food and has adaptations that help it capture the animals it preys upon |
| prey | An animal that a predator feeds upon |
| omnivore | An animal that eats both plants and animals |
| invertebrate | An animal that does not have a backbone. |
| vertebrate | An animal with a backbone |
| bilateral symmetry | Line symmetry; the quality of being divisible into two halves that are mirror images |
| radial symmetry | The quality of having many lines of symmetry that all pass through a central point |
| larva | The immature form of an animal that looks very different from the adult. |
| cnidarians | Animals whose stinging cells are used to capture their prey and defend themselves, and who take their food into a hollow central cavity. |
| polyp | The cnidarian body plan characterized by a vaselike shape and which is usually adapted for life attached to an underwater surface |
| medusa | The cnidarian body plan characterized by a bowl shape and which is adapted for a free-swimming life |
| regeneration | The ability of an organism to regrow body parts |
| anus | The opening at the end of an organism’s digestive system through which wastes exit |
| 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 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 | A mollusk with feet adapted to form tentacles around its mouth |
| arthropod | 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 arthropod that has two or three body sections, five or more pairs of legs, two pairs of antennae, and usually 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 complete metamorphosis, in which an insect is enclosed in a protective covering and gradually changes from a larva to an adult |
| gradual metamophosis | 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 | A stage 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 | A system of fluid-filled tubes in an echinoderm’s body |
