1. Fossils

2. Isn’t it just a “theory”? Evolution is a theory, but a theory is an explanation of a phenomena that is based on factual observations

3. I.Evolution A. Evolution: the changes of populations over generations

4. B. Fossil evidence: we use fossils to help explain the evolution of organisms 1. Fossil: any trace left behind by a living thing a. Mineralized bones b. Eggs c. Teeth d. Footprints

5. 2. Types of Fossils a. Mold: an imprint in rock

6. b. Cast: a mold that is filled with hardened minerals, a rock like model of a fossil

7. C. What do fossils tell us? 1. Relative Age: A given fossil is younger or older than another fossil

8. 2. Absolute Age: age in years of a fossil 3. Law of superposition: layers (strata) of rock and soil were deposited upon each other by wind and water i. Lowest Strata = Oldest ii. Highest Strata = Most recent

9. 4. Fossils that were found in the strata tell: i. When a species appeared ii. When it existed for a while iii. When it became extinct

10. 5. Mass extinction: brief period of time when large numbers of species disappeared

11. 6. Biogeography: study of geographical distribution of fossils and living organisms a. New organisms arise where similar forms already lived