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Transcript
Photosynthesis has changed the Earth’s atmosphere, oceans and rock deposition Prokaryotes were the first organisms to perform photosynthesis about 3.5 billion years ago. CO2 released from volcanic gassing “feeds” these photosynthetic prokaryotes. O2 reacts with UV light to form O3…ozone. Many groups of multicellular organisms were evolving. Amounts of CO2 begin to decrease, O2 begins to increase to about 2% about 2.5 billion years ago. But the O2 didn’t build up in the atmosphere yet. Where did it go? It dissolved in the oceans and oxidized the iron that was also dissolved in the water and precipitate onto the sea bed. These are the most important iron ores, for us, we get most of our steel from these ores…thanks to photosynthetic prokaryotes. Reservoirs of oxidizable rock became saturated about 1 billion years ago, so the free oxygen began to build up in the atmosphere to about 20%.
