Download Photosynthesis and the Earth

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%.