macy vocab

4. The required for half of the amount of a radioactive parent element to decay into a stable daughter element.
6. the biological mechanism by which organisms adjust to new environments or to changes in their current environment
7. eon:The time in Earths history from 542 million years ago to the present.
8. eon: The time from 2.5 to 0.542 billion years ago.
11. Small, early continents.

1. a species, family, or other group of animals or plants) having no living members; no longer in existence.
2. eon: The first 640 million years of Earth history.
3. decay: The process by which an unstable element naturally changes into another element that is stable.
5. The preserved remains or evidence of past living organisms.
8. of superposition: Principle that states that in rock layers that have not been folded or deformed, the oldest rock layers are on the bottom.
9. eon: The time from about 4 to 2.5 million years ago.
10. time scale: A chart that divides Earth’s history into different time units based on changes in the rock and fossils.