| A | B |
|---|
| gill slits | paired openings used for breathing |
| endotherm | vertebrates with a constant body temperature |
| endoskeleton | the internal skeleton |
| estivation | inactivity in summer |
| spawning | males swim over the eggs and release sperm |
| ectotherm | body temperature changes with environment |
| notochord | dorsal structure that becomes the backbone in vertebrates |
| amphibian | ectothermic land and water animal |
| swim bladder | structure that allows a fish to go up or down in the water |
| buoyancy | the ability of a liquid or gas to exert an upward force |
| reptile | an ectothermic animal with dry skin |
| tympanic membrane | structures used by frogs to hear |
| scales | hard, thin, overlapping plates used for protection |
| fins | fan-like steering structures in fish |
| biological indicators | species that are sensitive to changes in the environment |
| chordate | every vertebrate is also this |
| dorsal hollow nerve cord | bundle of nerves above the notochord |
| hibernation | inactivity in winter |
| amniotic egg | provides a complete environment for the embryo |
| adaptatiion | makes an organism better able to survive its environment |
| fish | cold-blooded vertebrae |
| cartilage | tough, flexible tissue |
| photolyase | an enzyme produced that lets some organisms repair damage of ultraviolet light |
