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.

Question

Quizplus · Accepted Answer

Oxygenic photosynthesis by cyanobacteria significantly increased the amount of oxygen in the atmosphere. This process involved the conversion of light energy into chemical energy, which was used to split water molecules and release oxygen as a byproduct. This led to the oxygenation of the atmosphere and the eventual rise of aerobic respiration in eukaryotic organisms.

Multicellularity and Large Body Size of Eukaryotic Organisms Require High