1. Big Ideas from Chapter 26 4.6 billion years in Earth’s history Much change has taken place Abiotic --> Life Many changes in the abiotic environment

2. 4 stages: Conditions of early Earth allow for abiotic synthesis of small molecules Small molecules build more complex polymers Polymers are packaged into protobionts Self replicating molecules allow for inheritance

3. Protobionts droplets of abiotically produced molecules including carbohydrates, lipids, amino acids, and ultimately nucleic acid Like cells: exhibit simple reproduction, internal environment protected within a membrane, simple enzymatic metabolism (breakdown of molecules to release energy)

4. Major shifts in life Protobiont --> prokaryotes Prokaryotes --> Eukaryotes Life colonizes the land

5. Prokaryotes Bacterial cells capable of producing substances required by the cell Prokaryotic autotrophs - cyanobacteria - can assemble organic compounds needed to survive Prokaryotic heterotrophs can use the products released by the autotrophs or feed on them directly

6. Oxygen Revolution Photosynthetic cyanobacteria - O2 given off as a byproduct - oxygen begins to accumulate in Earth’s atmosphere Changing environment - selection

7. Rise of Eukaryotes For a long time, prokaryotes are the sole inhabitants of Earth Eventually, eukaryotes evolve through endosymbiosis

8. Endosymbiosis Read the definition of endosymbiosis on the board Talk with your neighbor - can you think of any endosymbiotic relationships between species?

9. Endosymbiosis The mutualistic endosymbiotic relationship between different prokaryotes lead to eukaryotes - complex cells with specialized organelles Videos

10. Endosymbiosis Evidence supporting endosymbiosis: DNA Electron transport chains Enclosed in internal membrane Cell division of organelles resembles binary fission

11. Multicellularity Similar eukaryotic cells begin living in colonies and continue to specialize further Multicellular organisms are comprised of different specialized cell types

12. Evolution Life changes over time Natural selection Unplanned and responsive to changing conditions of the environment Many scientists are investigating the notion of change over time - both abiotic and biotic