natural selection

3. Selection the theory that states organisms best suited for their environment will survive and pass their favorable traits on to their offspring
4. a fossil that forms the perfect shape of the organism
8. the amount of time it takes for half of the atoms to decay
9. where the actual remains of fossils may be found
11. a break in Earth's crust
12. the way an organism is made (phenotype) that helps the organism survive in its environment
13. a disturbance in one or more layers of Earth's crust; surface where new rock layers meet a much older rock surface beneath them
14. magma that has cooled outside of Earth's crust
15. a scientist who studies fossils

1. a behavior of an organism that helps it survive in its environment
2. the law that states "in layers of undisturbed rock layers, the oldest layers will be on the bottom and the youngest will be on top"; the way to determine relative
5. a fossil that tells evidence of the activity of organisms
6. magma that has cool inside Earth's crust
7. minerals replace all or part of the organism
10. a genetic change in the cells of an organism which may lead to favorable or unfavorable changes in the organism