Fossils
- 1. Fossils
- 2. Objectives Classify the processes that lead to fossil formation Understand key concepts in the study and use of fossils Describe the importance of index fossils
- 3. Fossilization Frequency? Rare Event How? Organism dies and becomes buried in sediments
- 4. Key concepts of Fossils Fossils represent the remains of once-living organisms Most fossils are the remains of extinct organisms The same fossils found in different rock layers indicate they are the same age
- 5. Four types of fossils
- 6. Petrified Fossils The tissues of organism are slowly replaced by minerals Organism turns into stone
- 7. Mold Organism is completely dissolved, but leaves a space in rock
- 8. Cast Mold can fill later with minerals and harden into shape of organism
- 9. Preserved Remains Organism trapped in preservative Amber Ice
- 10. Relative Dating Layers of sediment are laid down in order Oldest layers are on the bottom Layers must remain undisturbed Therefore fossils in deeper layers must be older than fossils in top layers 156
- 11. Radioactive Dating When organism dies it stops consuming radioactive material All radioactive chemicals decay at a specific rate Half-life = amount of time for half of the material to decay The amount of decay within fossil will determine its age 158
- 12. Mass Extinction Times in fossil evidence when many things stop appearing in one layer Event has occurred multiple times in Earth’s history Called a mass extinction event Why? Climate change Asteroid impact 162
- 13. Gradualism Organisms change slowly over time Fossil evidence shows long periods of time with no change Often changes occur rapidly within a fossil layer Incomplete fossil records 163
- 14. Punctuated Equilibria Organisms change rapidly in a short period of time Some change gives a huge advantage and that organism replaces others Long periods of no change, “Stability” in fossil record 163
- 15. Describing a million Close your eyes and when I say, “go” mentally time one minute Raise your hand and open your eyes when you think one minute has passed Sit quietly until everyone has raised their hand (ready) Was it easy or hard to count one minute? Is it easy or hard to think about how much time is let till the end of the school year? Is it easy to picture how big a million is?
- 16. Fossilization Frequency? Rare Event How? Organism dies and becomes buried in sediments
- 17. Key concepts of Fossils Fossils represent the remains of once-living organisms Most fossils are the remains of extinct organisms The same fossils found in different rock layers indicate they are the same age
- 18. Four types of fossils Petrified Fossils The tissues of organism are slowly replaced by minerals Organism turns into stone Molds Organism is completely dissolved, but leaves a space in rock Casts Mold can fill later with minerals and harden into shape of organism Preserved Remains Organism trapped in preservative Amber Ice
- 19. Homework Describe how fossils form