oxygenic photosynthesis developed
~2.5 b.y.a. (end-Archaean)
O2 accumulated, raising level from
0.01% of atmosphere then to 20% today
(~10% at ~0.5 b.y.a. - first vertebrates)
first O2 photosynthesizers were probably
just like today's Cyanobacteria
dominated 2.5 - 0.6 b.y.a. - stromatolites
global primary production
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