The evolution of photosynthesis

Abstract

The merits of the inductive and the deductive approach in tracing the pathways of evolution is discussed. Using the latter approach, it is concluded that photosynthesis followed fermentation as a method of obtaining energy-rich compounds, especially ATP. Photosynthesis probably arose by utilization of membranes for bioenergetic processes. Originally photosynthesis served photophosphorylation (ATP production), later reducing power was also made, either by open-ended, light-powered, electron flow or driven by ATP; ultimate electron donors were at first hydrogen or sulfur compounds, and later water. The last-named capability was acquired by prokaryotic algae, the earliest plants, similar to the recent blue-greens. When free oxygen entered the atmosphere for the first time, various forms of respiration (oxidative phosphorylation) became possible. Mechanistically, respiration evolved from photosynthesis ("conversion hypothesis"). Prokaryotic algae are probably the ancestors of the chloroplasts in the eukaryotes. In the evolution of the eukaryotes, not much change in the basic processes of photosynthesis occurred. © 1977.