| A | B |
|---|
| animal | Multicelled |
| annelid | A member of phylum Annelida; segmented worm such as earthworm. |
| arthropod | Invertebrate with hard exoskeleton and specialized segments with jointed appendages. |
| bilateral symmetry | A body shape with right and left halves that are approximately mirror images of one another. |
| brain | Of most nervous systems;integrating center that receives and processes sensory input and issues coordinated commands for responses by muscles and glands. |
| cephalization | Over time the concentration of sensory structures and nerve cells in a head. |
| cnidarian | Type of radial invertebrate at the tissue level of organization; the only nematocyst producer. |
| coelom | A peritoneum-lined cavity between the gut and body wall of most animals. |
| contractile cell | A cell that shortens in response to stimulation and returns to a resting position. |
| cuticle | In annelids this is a thin flexible coat. In arthropods it is a lightweight exoskeleton hardened with protein and chitin. |
| deuterostome | Bilateral animal in which the anus forms from first indentation in the embryo examples are echinoderms and chordates |
| echinoderm | Type of invertebrate with calcified spines or plates on body wall. Radial with some bilateral features examples include starfish |
| ectoderm | The first-formed outermost primary tissue layer of animal embryos; gives rise to nervous system tissues and integument's outer layer. |
| endoderm | Inner primary tissue layer of animal embryos; source of inner gut lining and derived organs. |
| epithelium | Animal tissue that covers external surfaces and lines internal cavities and tubes. |
| exoskeleton | External skeleton usually the hardened cuticle of arthropods |
| flatworm | One of the simplest invertebrates having organ systems; includes turbellarians such as planaria and flukes or tapeworms. |
| gonad | Primary reproductive organ in which animal gametes are produced. |
| gut | Generally;a sac or tube from which food is absorbed into internal environment. Also a gastrointestinal tract hermaphrodite |
| hydrostatic skeleton | A fluid-filled cavity or cell mass against which contractile cells act. |
| invertebrate | Any animal without a backbone. |
| larva | Immature stage between an embryo and adult in many animal life cycles. |
| malpighian tubule | One of many small tubes that help land-dwelling insects dispose of toxic wastes without losing precious water. |
| mantle | In mollusks this is a tissue draped over the visceral mass. |
| medusa | Of cnidarian life cycles this is a free-swimming bell-shaped stage with oral lobes and tentacles extending below the bell. |
| mesoderm | Primary tissue layer of all large |
| metamorphosis | changes in body form of certain animals; and remodeling of body parts leads to adult form. |
| mollusk | Only invertebrate with mantle draped over a soft;fleshy body; most have an external or internal shell. |
| molting | Periodic shedding of worn-out or too-small body structures. Permits some animals to grow in size or renew parts |
| nematocyst | Cnidarian capsule that has a dischargeable tube-shaped thread and sometimes barbed; releases a toxin or sticky substance. |
| nephridium | Unit that controls composition and volume of fluid in some invertebrates such as the earthworm |
| nerve cell | One of the cells that receive and integrate signals from sensory receptors. |
| nerve cord | A prominent longitudinal nerve; Chordate nervous systems arise from a dorsal nerve cord. |
| nymph | Immature post-embryonic stage of some insect life cycles. |
| organ | Body structure with definite form and function that consists of more than one tissue. |
| organ system | Organs interacting chemically and physically in a common task. |
| pharynx | Among invertebrates a muscular tube to the gut |
| placozoan | The simplest known animal; tiny and asymmetrically soft-bodied with two cell layers. |
| planula | Larva usually with ciliated epidermis. Swims or creeps; may resemble first animals. |
| polyp | Vase-shaped and sedentary stage of cnidarian life cycles. |
| proglottid | One of many tapeworm body units that bud in sequence behind the scolex. |
| protostome | Lineage of coelomate bilateral animals that includes mollusks; annelids; and arthropods. The first indentation to form in protostome embryos becomes the mouth. |
| pupa | An immature and post-embryonic stage of many insect life cycles. |
| radial symmetry | Animal body plan having four or more roughly equivalent parts around a central axis roundworm |
| sponge | Animal with no body symmetry and no tissuesand phagocytic collar cells in its body wall. |
| water vascular system | Unique hydraulic system of echinoderms; functions in locomotion and feeding. |
| acoelomate | Absence of a fluid-filled cavity between gut and body wall. |
