Big Ideas from Chapter billion years in Earth’s history Much change has taken place Abiotic --> Life Many changes in the abiotic environment
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
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)
Major shifts in life Protobiont --> prokaryotes Prokaryotes --> Eukaryotes Life colonizes the land
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
Oxygen Revolution Photosynthetic cyanobacteria - O2 given off as a byproduct - oxygen begins to accumulate in Earth’s atmosphere Changing environment - selection
Rise of Eukaryotes For a long time, prokaryotes are the sole inhabitants of Earth Eventually, eukaryotes evolve through endosymbiosis
Endosymbiosis Read the definition of endosymbiosis on the board Talk with your neighbor - can you think of any endosymbiotic relationships between species?
Endosymbiosis The mutualistic endosymbiotic relationship between different prokaryotes lead to eukaryotes - complex cells with specialized organelles Videos
Endosymbiosis Evidence supporting endosymbiosis: DNA Electron transport chains Enclosed in internal membrane Cell division of organelles resembles binary fission
Multicellularity Similar eukaryotic cells begin living in colonies and continue to specialize further Multicellular organisms are comprised of different specialized cell types
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