1. The History of Life Chapter 12

2. In the Beginning Earth is 4.6 billion years old Primitive atmosphere formed 4 billion years ago H 2 O, CO, CO 2, N 2, H 2 S, HCN released by volcanic eruptions and meteorites Cyanobacteria used H 2 S for photosynthesis fossils of prokaryotic cells called stromatolites are 3.5 billion years old

3. 1953 Stanley Miller Harold Urey Experiment UCSD

4. An Aerobic planet ☬ Oxygen concentration rose, caused mass extinction of anaerobic organisms and dominance or aerobic species ☬ Oxygen rose into stratosphere, formed ozone shield, allowed species to inhabit land

5. How Time Transforms Organic Matter

6. Fossils RRange in age from 3.5 billion years old (Cyanobacteria) to 10,000 years old (species from the last ice age) FFormed in sedimentary rock, most often found in limestone, sandstone, or shale.

7. Radiometric Dating Measures the natural decay rate of unstable isotopes Determines the relative age of fossils Carbon in its stable state contains 6 protons and 6neutrons Carbon 14 contains two extra neutrons, it is an isotope, it is radioactive

8. Radiometric Dating The oldest fossils are at the bottom of the rock column

9. Geological time scale oldest Current day

10. 1 2 3 4 5 Mass extinction 25-70% of species wiped out Extinction is followed by a period of episodic speciation