Multicellularity and large body size of eukaryotic organisms requires high metabolic rates and efficient ATP production by aerobic respiration. How did bacteria change Earth's atmosphere to enable aerobic respiration?
A) Nitrogen fixation by cyanobacteria decreased the amount of nitrogen in the atmosphere, leading to simultaneous increase of oxygen.
B) Splitting of water during anaerobic respiration by cyanobacteria dramatically increased the amount of oxygen in the atmosphere.
C) Oxygenic photosynthesis by cyanobacteria significantly increased the amount of oxygen in the atmosphere.
D) Anaerobic respiration by cyanobacteria increased the amount of oxygen in the atmosphere by reducing the amount of iron oxides that are 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 involves the conversion of water and carbon dioxide into oxygen and carbohydrates. Cyanobacteria were the first organisms to have this process, and they paved the way for the evolution of aerobic respiration in organisms with larger body sizes. The increased amount of oxygen in the atmosphere also allowed for the development of the ozone layer, protecting living organisms from harmful UV radiation.

Multicellularity and Large Body Size of Eukaryotic Organisms Requires High