| A | B |
|---|
| Birds | endothermic vertebrates with an outer covering of feathers and wings |
| contour feathers | large feathers that cover a bird's body and wings |
| flight feathers | contour feathers used for flying |
| barbs | side branches that grow from the quill of a contour feather |
| down feathers | short, soft, and fluffy feathers that insulate a bird's file |
| powder feathers | feathers that release a waterproofing powder |
| Archaeopteryx | early birdlike animal from the Jurassic period |
| crop | organ that stores food and moistens it |
| gizzard | gravel-containing food grinder |
| air sacs | make a bird's body more buoyant |
| four chambered | type of heart a bird has |
| uric acid | birds eliminate nitrogenous waste in this form |
| cerebrum | controls flying, nest building, care of young, and mating |
| cerebellum | coordinates movement and life processes |
| medulla | very much like that of a reptile |
| olfactory lobes | very small in a bird's brain |
| keel | where the chest muscles attach |
| shell gland | forms the shell around the egg |
| chalaza | keeps the yolk in the center of the shell |
| yolk | supplies nutrients for the embryo |
