| A | B |
|---|
| atmosphere | air that surrounds the earth |
| barren | unable to produce and support much plant life |
| bison | a shaggy animal with hooves, horns, and a humped back |
| ecological | having to do with the relationship of living things and the environment |
| famine | a widespread, dangerous lack of food |
| interglacial | warm time between ice ages |
| marrow | the soft tissue inside bones |
| megafauna | very large animals |
| microbe | very tiny living thing, germ |
| obscure | to hide something from view |
| previously | before; at an earlier time |
| retreat | to go back; to withdraw |
| yield | amount produced |
| expedition | a journey taken for a specific reason |
| extinct | no longer existing |
| artistic ability | cave drawings of the Ice Age people best show their X. |
| North America | By about 22,000 years ago, groups of people began moving into X |
| Greenland and Antarctica | Both are covered by ice from the Ice Age |
| 1/3 of the earth | During the Ice Age, ice covered X |
| The Ice Age ended X years ago | 10, 000 |
