| A | B |
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| Annelida | A phylum of animals with bodies made up of many similar segments; segmented worms |
| anterior | Pertaining to the front, or head, end of a bilateral symmetricla animal |
| bilateral symmetry | A type of summetry in which the division of the organism results in two parts that are mirror images of each other |
| bivalve | A member of the class Bivalvia, including clams, oysters, mussels, and scallops; a mollusk having a two-part, hinged shell and no head or radula |
| cephalopod | A member of the class Cephalopoda, including the octopus, squid, and nautilus; a mollusk having a distinct head and tentacles |
| cnidoblast | a stinging cell found in coelenterates, which is used for defense and capturing food |
| Coelenterata | A phylum consisting of hydras, jellyfish, and corals; cup shaped animals with hollow gut |
| coelom | the fluid-filled body cavity between the body wall and the digestive tube |
| collar cell | A type of flagellated cell found in the inner layer of a sponge |
| dorsal | Pertaining to the upper side or back of a bilaterally symmetrical animal |
| foot | A large ventricle, muscular structure that functions in locomotion in mollusks |
| gastropod | A member of the class Gastropoda , including snails, slugs, and whelks; a mollusk having a head with tentacles and a one-piece, straight, or spiral shell |
| gastrovascular cavity | The internal body cavity of a coelenterate |
| gemmule | A group of cells enclosed in a tough outer covering |
| invertebrate | Any animal without a backbone |
| larva | An early developmental stage of some animals after hatching; must undergo metamorphosis to reach adult form |
| mantle | A fold of skin that surrounds the body organs in mollusks and secretes the shell of shelled mollusks |
| medusa | The body form of free-swimming coelenterates |
| mesoglea | A jelly-like protein that seperates the layers of coelenterates |
| Mollusca | A phylum of invertebrates having soft, unsegmented bodies, often enclosed in a mantle; mollusks |
| nematocyst | The capsul within a cnidoblast containing a coiled, hollow thread that is discharged when the cnidoblast is stimulated |
| Nematoda | A phylum of invertebrates with cylindrical bodies covered by a heavy cuticle; roundworms |
| osculum | An opening at the unattached end of a sponge that serves as an excurrent opening |
| parapodium | Paired, paddlelike extentions found on each segment of some annelids; used for swimming and creeping |
| pharynx | The throat |
| planula | The small, ciliated larva of many coelenterates |
| Platyhelminthes | Meaning flatworms; simplest invertebrates showing definate head and tail |
| polyp | The sessile body form of a coelenterate |
| pore | A tiny opening found in plant leaves and animal skins through which fluids are absorbed or discharged |
| Porifera | A phylum of the simplest multicellular animals; aquatic, immobile animals with an outer layer pierced by many pores; sponges |
| posterior | Pertaining to the rear or tail end of a bilaterally symmetrical animal |
| proglottid | Any of the segmentlike divisions of a tapeworms body |
| radial symmetry | An organism with a central axis running the length of the animal from top to bottom, front to rear |
| radula | A rasping, tonguelike organ in mollusks |
| spherical symmetry | Organisms in the shape of a sphere, any cut through the center divides the organism into two matching halves |
| spicule | A small skeletal structure embedded in the middle layer of sponges that provides support and gives shape to the sponge |
| sponging | Flexible fibers made up of protein |
| trochophore | A type of free-swimming, ciliated larva |
| ventral | Pertaining to the lower or belly side of a bilaterally symmetrical animal |
| vertebrate | Any animal with a back bone, including mammals, fishes, birds, reptiles, and amphibians |
| zoology | a branch of biology that deals with the study of animals |
