1. Paleontology Fossils and the History of Life on Earth

2. Fossils Remains or traces of ancient life Bones, Teeth, Shells, Tracks, Trails Soft tissues – rare Preservation is favored by –Hard parts –Rapid burial

3. How does an organism become a fossil? Rapid burial is essential Protection from scavengers, decomposers, physical deterioration More likely to be preserved if organism has “hard parts”

4. What conditions favor preservation? Rapid burial is most likely in ocean Many sea creatures have shells So… Marine organisms with shells are most likely to become fossils Other organisms are less easy to preserve. Therefore: Fossil record is biased – many creatures were never preserved

5. Types of Preservation Original shell, bone or teeth Altered hard tissue (replaced by different minerals) Molds and Casts Trace fossils: burrows, tracks, trails Soft Tissues –Carbon film –Amber –Mummified –Frozen

6. Original Hard Material

7. Altered Hard Material

8. Molds and Casts

9. Carbon Film

10. Amber

11. Impression and Carbon film

12. Carbon Film - Plants

13. Utility of Fossils History of Life on Earth Evolution – appearances of new species Extinction – disappearances of species Framework for other events in Earth’s History Guide in exploring for fossil fuels

14. Mile Markers in Deep Time Periods of time can be recognized by the music of that time Similarly, each interval of Earth History is characterized by a unique set of living creatures

15. Mile Markers in Deep Time Life is unique for each interval of time because of evolution and extinction Volcanos, earthquakes, mountains, types of rocks repeat throughout history Life does not repeat – it is directional Therefore, we can place other Earth events in a framework based on fossils

16. Mile Markers in Deep Time The fossil-based framework for Earth history is known as the GEOLOGIC TIME SCALE Units: Eras, Periods, Epochs, Ages

17. Summary Remains or traces of ancient life Preservation is favored by –Hard parts –Rapid burial Shelled marine organisms are most likely to fossilize Fossil record is biased

18. Summary Fossils may be preserved as –Original shell, bone or teeth –Altered hard tissue (replaced by different minerals) –Molds and Casts –Trace fossils: burrows, tracks, trails –Soft Tissues Carbon film AmberMummifiedFrozen

19. Summary Fossils document the history of life on Earth Fossils are proof of evolution and extinction Fossils provide a framework for other events in Earth’s history This framework is the Geologic Time Scale