| A | B |
|---|
| Amniotic egg | egg covered with a shell that provides a complete environment for the embryo’s development; for reptiles, a major adaptation for living on land |
| Cartilage | tough; flexible tissue that joins vertebrae and makes up all or part of the vertebrate endoskeleton; in humans, thick, smooth, flexible, and slippery tissue layer that covers the ends of bones, makes movement easier by reducing friction, and absorbs shocks |
| Chordate | animal that has a notochord, a nerve cord, pharyngeal pouches, and a postanal tail present at some stage in its development |
| Ectotherm | vertebrate animal whose internal temperature changes when the temperature of its environment changes |
| Endoskeleton | supportive framework of bone and/or cartilage that provides an internal place for muscle attachment and protects a vertebrate’s internal organs |
| Endotherm | vertebrate animal with a nearly constant internal temperature |
| Estivation | inactivity in hot, dry months |
| Fin | structure used by fish for steering, balancing, and movement |
| Hibernation | inactivity in cold weather; cyclic response of inactivity and slowed metabolism that occurs during periods of cold temperatures and limited food supplies |
| Nerve cord | tubelike structure above the notochord that in most chordates develops into the brain and spinal cord |
| Notochord | firm but flexible structure that extends along the upper part of a chordate’s body |
| Pharyngeal pouches | in developing chordates, the paired openings found in the area between the mouth and digestive tube |
| Postanal tail | muscular structure at the end of a developing chordate |
| Scales | thin, hard plates that cover a fish’s skin and protect its body |
| Vertebrate | animal with a backbone |
