| A | B |
|---|
| bird | An endothermic vertebrate that has feathers, a four-chambered heart, and lays eggs. |
| contour feathers | A large feather that helps give shape to a bird's body. |
| down feathers | Short fluffy feathers that trap heat and keep a bird warm. |
| insulator | A material that does not conduct heat well and which therefore helps prevent it from escaping. |
| crop | A bird's internal storage tank that allows it to store food inside its body after swallowing it. |
| gizzard | A thick-walled, muscular part of a bird's stomach that squeezes and grinds partially digested food. |
| lift | The difference in pressure between the upper and lower surfaces of a bird's wing that produces an upward force that causes the wing to rise. |
| mammal | An endothermic vertebrate with a four-chambered heart, skin covered with fur or hair, and which has young fed with milk from the mother's body. |
| premolars | Teeth that, along with molars, gring and shred food into tiny bits. |
| mammary gland | The organs that produce the milk with which mammals feed their young. |
| incisors | Flat-edged teeth used to bite off and cut parts of food. |
| molars | Teeth that, along with premolars, grind and shred food into tiny bits. |
| canines | Sharply pointed teeth that stab food and tear into it. |
| diaphragm | A large muscle in a mammal's chest that functions in breathing. |
| monotreme | A mammal that lays eggs. |
| marsupial | A mammal whose young are born alive at an early stage of development, and which usually continue to develop in a pouch on their mother's body. |
| gestation period | The length of time between fertilization and birth of an animal. |
| placental mammal | A mammal that develops inside its' mother's body until its body systems can function independently. |
| placenta | An organ in pregnant female placental mammals that passes materials between the mother and the developing embryo. |
