How Oxygen (increased) And Carbon Dioxide (decreased) Changed in the Atmosphere

How was oxygen introduced into the atmosphere

Algae & plants produced the O2 that is now in the atmosphere by photosynthesis

Equation for photosynthesis

6CO2 + 6H2O -> C6H12O6 + 6O2

carbon dioxide + water –(light)-> glucose + oxygen

When did algae first produce oxygen

Algae first produced oxygen about 2.7 billion years ago and soon after this oxygen appeared in the atmosphere

How have oxygen levels increased

Algae first produced oxygen about 2.7 billion years ago and soon after this oxygen appeared in the atmosphere

How did Carbon Dioxide Levels decrease

Algae and plants decreased the % CO2 in the atmosphere by photosynthesis

How else did Carbon Dioxide decrease (fossil fuels)

-CO2 was also decreased by the formation of sedimentary rocks that contain carbon (e.g. limestone and coal)

-and by the production of fossil fuels from the remains of dead plants and animals when they decayed