1. The Origin of Life Notes: Chapter 14

2. The Beginning:  Earth is about 4.6 billion years old  Life began on Earth about 3.5 billion years ago in the ocean

3. Evidence of Life:  Fossils: remains of organisms, found in sedimentary rock  Relative Dating: lower rocks are older than higher ones  Radiometric Dating: using radioactive isotopes in rocks because rate of decay is related to half-life

6. Relative Dating:

7. Radiometric Dating:

8. How does life arise?  Spontaneous generation: life from nonliving things –Francesco Redi: disproved theory by showing that flies must come from other flies

9. How does life Arise?  Spontaneous generation: –Louis Pasteur: concluded that microorganisms must come from other microorganisms using S- shaped flasks that let in only air = no organisms

10.  Biogenesis: life only from other living things –Miller & Urey: showed that organic molecules could have formed the beginning of life

11. The origin of cells:  Anaerobic prokaryotes: lived in an atmosphere with no oxygen 

12. The origin of cells:  Aerobic organisms: evolved once photosynthesis released oxygen

13. The origin of cells:  Prokaryotes: cells without a nucleus or organelles  Eukaryotes: cells with a nucleus and organelles –cells grew in complexity once conditions for life improved