An endothermic vertebrate that lays eggs and has feathers and a four-chambered heart.
A large feather that helps give shape to a bird's body.
A short, fluffy feather that traps heat and keeps a bird warm.
An internal organ of many birds that stores food inside its body after swallowing it.
A muscular, thick-walled part of a bird's stomach that squeezes and grinds partially digested food.
The difference in pressure between the upper and lower surfaces of a bird's wings that produces an upward force that causes the bird to rise.
An endothermic vertebrate with a four-chambered heart and skin covered with fur or hair, that feeds its young with milk from the mother's body.
A large muscle located at the bottom of a mammal's rib cage that functions in breathing.
A mammal that lays eggs.
A mammal whose young are born at an early stage of development, and which usually continue to develop in a pouch on their mother's body.
The length of time between fertilization and birth of a mammal.
A mammal that develops inside its mother's body until its body systems can function independently.
A membrane that becomes the link between the developing embryo or fetus and the mother
An organ in female mammals that produces milk for the mammal's young.