| A | B |
|---|
| vertebrate | an animal with a backbone |
| gill | structure through which oxygen is obtained |
| coldblooded | having a body temperature that changes with the environment |
| warmblooded | having a constant body temperature |
| external fertilization | fertilization that takes place outside the female's body |
| internal fertilization | fertlization that takes place within the body of the female |
| swim bladder | air-filled sac enabling bony fish to rise or sink in water |
| metamorphosis | dramatic change in appearance due to development |
| phylum Chordata | taxonomic group that contains all vertebrates (chordates) |
| notochord | a long, flexible supporting rod (in us, our vertebral column) |
