photosynthesis


Size of fossils throughout history and the two sharp increases in atmospheric O2 from photosynthesis. Oxygen is shown as percentage of present atmospheric levels (PAL) during the Archaean, Proterozoic and Phanerozoic geological eons. Adapted from ”Two-phase increase in the maximum size of life over 3.5 billion years reflects biological innovation and environmental opportunity.” by JL Payne et al. (2009) Proc Natl Acad Sci USA 106: 24-27. Adapted with permission.

Photosynthesis is the process by which solar energy is absorbed by some living organisms (plants, algae and certain bacteria), converted and stored as chemical energy.

Based on geological evidence photosynthesis-capable organisms are estimated to have appeared more than 3 billion years ago. The first organisms to successfully utilize energy from sunlight were most likely anoxygenic (non-oxygen evolving), and used hydrogen peroxide as the primary electron donor, and before that ferrous iron [1]. The greatest leap in innovation of the photosynthetic mechanism was the transition to oxygenic photosynthesis. The use of water as the primary electron source, and the subsequent release of O2 changed the composition of the Earth’s atmosphere starting approximately 2.4 billion years ago [2]. Oxygenic photosynthesis and its by-product O2 changed Earth’s environment to such an extent that it affected the evolution of life, allowing for organisms to grow in size and complexity . During millennia photosynthesis evolved and diversified to become an efficient energy-harvesting mechanism in all environments.