| A | B |
|---|
| vertebrate | animals with backbones |
| cartilage | tough material that is flexible and later forms bones |
| endotherms | animals that have a stable body temperature (warm-blooded) |
| ectotherms | animals that rely on their environment for their temperatures (cold-blooded) |
| fins | fan-shaped structures that help fish move |
| scales | protect the body of a fish and lower the amount of friction |
| lateral line | row(s) of tiny sense organs that detect water vibrations |
| gills | an organ that removes oxygen from the water |
| external fertilization | females lays unfertilized eggs into the water and the male fertilizes them |
| jawless fish | fish without jaws |
| cartilaginous fish | strong swimmers and expert predators |
| bony fish | have many bones; largest group of fish |
