| A | B |
|---|
| lift | the force that allows a bird to stay in the air |
| contour feathers | feathers birds use for flying |
| Cetacea | order including largest mammals |
| herbivores | plant eaters |
| marsupials | pouched mammals |
| sternum | the breastbone that supports large chest muscles |
| mammals | produce milk for their young, warm blooded and have hair |
| gestation period | the length of time necessary for the embryo to develop in the uterus |
| mammary glands | glands that produce milk |
| joey | a young kangaroo |
| incisors | specialized teeth in mammals that bite and cut |
| omnivores | animals that eat both plants and animals |
| hollow bones | makes a bird lighter |
| sea otter | a carnivorous placental mammal with a well-developed brain and good underwater vision |
| incubate | process of keeping eggs warm |
| umbilical cord | structure containing blood vessels that attaches embryo to the placenta |
| thrust | the motion of a bird that goes forward |
| placenta | organ developed by embryo that attaches to the uterus |
| preening | activity of rubbing oil into feathers |
| placental mammals | mammals whose embryos develop inside a uterus |
| monotremes | mammals that lay eggs with tough, leathery shells |
| carnivores | flesh eating |
| down feathers | feathers that help to insulate |
