| A | B |
|---|
| endoskeleton | internal support structure |
| exoskeleton | outer protective layer |
| notochord | flexible skeletal rod |
| endotherms | have constant body temperatures |
| ectotherms | body temperature changes with outside temperatures |
| fish | have streamlined bodies with fins and gills |
| jawless fish | did not have jaws, |
| cartilaginous fish | fish without bones, made up of flexible cartilage |
| bony fish | have skeletons made of bones |
| gills | organs that remove dissolved oxygen from the water |
| lampreys, and hagfish | examples of jawless fish |
| sharks, rays and skates are examples of | cartilaginous fish |
| cartilage | a firm and flexible connective tissue that makes up part of your skeletal system |
| swim bladder | a sac of air that allows a fish to rise and lower itself in water as it is swimming |
| scales | are covered with mucus which helps the fish move through water easily |
| fins | used for swimming and steering fish as the swim |
