| A | B |
|---|
| chordate | member of a group of animals that have a notochord in their ambryonic form |
| notochord | flexible rod that extends through much of the length of a chordate embryo |
| vertebra | segment of the backbone; encloses and protects the nerve cord |
| endoskeleton | skeleton located inside the body; characteristic of all vertebrates and som invertebrates |
| tetrapod | member of a group of animals with two sets of paired limbs modified as legs |
| cartilaginous fish | member of a group of fishes with flexible skeletons made intirely of cartilage |
| bony fish | member of a group of fishes with skeletons made mainly of bone |
| lateral line system | row of sensory organs running along each side of the body in fishes |
| operculum | protective flap covering the gills of bony fishes |
| swim bladder | gas-filled sac that controls buoyancy in fishes |
| amphibian | member of a group of invertebrates that includes fros, toads, and salamanders, most of which spend part of their life cycles in an aquatic environment and part in a terrestrial environment |
| tadpole | legless aquatic larva of an amphibian |
