| A | B |
|---|
| contour feather | strong, lightweight feathers that give a bird coloring and smooth shape |
| down feather | provide an insulating layer next to the skin of adult birds, cover the bodies of young birds |
| endotherm | maintain a constant body temperature |
| preening | using the bill or beak to rub oil from the oil gland over its feathers |
| mammal | endothermic vertebrates that have hair and produce milk to feed their young |
| mammary gland | produces milk for feeding young |
| omnivore | eat plants and other animals |
| carnivore | eats only the flesh of other animals |
| herbivore | eat only plants |
| monotreme | mammals that lay eggs with leathery shells |
| marsupial | mammal that gives birth to immature young that crawl into external pouch |
| placental | embryos completely develop inside the female's uterus |
| gestation period | time during which the embryo develops in the uterus |
| placenta | orgn that develops from tissues of the embryo and tissues that line the inside of the uterus |
| umbilical cord | transports food and oxygen from the placenta to the embryo and removes waste |
