Science

3. a record of the geologic events and the evolution of life forms as shown in the rock and fossil records.
5. an animal with a backbone.
8. the number of years that have passed since the rock formed.
10. dating to determine the absolute ages of rocks.
11. an animal that lives part of its life on land and part of its life in water
12. have scaly skin and lay eggs that have tough, leathery shells.
13. Eras are subdivided into units of geologic time
14. The preserved remains of living things
15. is a gap in the geologic record
18. the atoms of one element break down to form atoms of another

1. Many were animals without backbones
2. a rock Is the number of years that have passed since the rock formed.
4. a vertebrate that controls its own bodytemperature and feeds milk to its young.
6. of sedimentary ages of rock layers.
7. to determine the relative
9. an event during which many types of living things became extinct at the same time.
16. present into three long units of time
17. Geologists divide the time between the Precambrian and