Multicellularity and Large Body Size of Eukaryotic Organisms Require High

Multiple Choice

Multicellularity and large body size of eukaryotic organisms require high metabolic rates and efficient ATP production by aerobic respiration. How did bacteria change Earth's atmosphere to enable aerobic respiration?

A) Oxygenic photosynthesis by cyanobacteria significantly increased the amount of oxygen in the atmosphere.
B) Splitting of water during anaerobic respiration by cyanobacteria dramatically increased the amount of oxygen in the atmosphere.
C) Nitrogen fixation by cyanobacteria decreased the amount of nitrogen in the atmosphere, leading to the simultaneous increase of oxygen.
D) Anaerobic respiration by cyanobacteria increased the amount of oxygen in the atmosphere by reducing the amount of iron oxides that were able to react instantly with oxygen.