| A | B |
|---|
| amphibian | A vertebrate that usually lives in water in the early part of its life; it breathes with gills and then later develops lungs. |
| bird | A vertebrate that has wings, is covered with feathers, and hatches from a hard-shell egg. |
| exoskeleton | A hard outer structure, such as a shell, that protects or supports an animal’s body. |
| fish | A vertebrate that lives in water and has gills used for breathing and fins used for swimming. |
| gill | A feathery structure on each side of a fish’s head that lets the fish breathe underwater. |
| invertebrate | An animal that does not have a backbone. |
| mammal | A vertebrate, such as a cat, that has hair or fur and feeds its young with milk. |
| molt | To shed an out covering such as hair, outer skin, horns, or feathers at certain times. |
| organism | A living thing that can be classified as belonging to one of several kingdoms. |
| reptile | A vertebrate, such as a lizard or a crocodile, that has dry scaly skin and lays eggs that have a leathery shell. |
| vertebra | One of the bones that together make up the backbone. |
| vertebrate | An animal that has a backbone. |
