Species

4. tectonics- the movements as the result of solid "plates" moving slowly, as little as 3 cm a year, over Earth's mantle
5. Radiation- process where single species or a small group of species evolve over a relatively short period of time
6. theory- prokaryotic cells entered those ancestral eukaryotes
11. extinction- an event during which many species become extinct over a relatively short period of time
12. extinction- paleontologists use this to describe the kind of "business as usual" extinction
13. researchers who study fossils to learn about ancient life
15. eons are divided
16. Evolution needed to be slow and steady
17. fossils- distinctive fossils used to establish and compare the relative ages of rock layers and the fossils they contain
18. time scale- geologists and paleontologists have built a time line of Earth's history

1. Equilibrium- the terms used to describe equilibrium that is interrupted by brief periods or more rapid change
2. evolution-evolution produces similar structures and characteristics in distantly related organisms through this process
3. time required for half of the radioactive atoms in a sample to decay
4. Eras are subdivided
7. patterns- grand transformations in anatomy, phylogeny, ecology, and behavior, which usually take place in clades larger than a single species
8. is one that has died out
9. the process by which two species evolve in response to changes in each other over time
10. dating- relies on radioactive isotopes, which decay, or break down, into stable isotopes at a steady rate
14. Dating- places rock layers and their fossils in a temporal sequence