Metabolism is the biochemical network that supplies the energy and building blocks for all cells on Earth. The collective metabolism of all cells in turn mediates the global biogeochemical cycles, which regulate Earth's climate. Reconstructing metabolic evolution provides a powerful lens for linking evolutionary dynamics across levels of biological organization and for understanding the chemical co-evolution of Earth and the biosphere. I will illustrate these ideas using globally abundant oceanic phytoplankton and co-occurring bacteria as a model system. I will argue this system evolved through a sequence of "niche constructing adaptive radiations" that drew down nutrient levels in the surface oceans, thereby increasing total ecosystem biomass, while also increasing levels of dissolved organic carbon. I will further argue this evolutionary dynamic produced a collective mutualism in oceanic microbial ecosystems that is highly similar to that of organelles within plant cells. Finally I will argue that the evolutionary self-organization of oceanic microbial ecosystems contributed to the Neoproterozoic-Phanerozoic oxygenation of Earth, and more generally that the rise of atmospheric oxygen reflects an increasing metabolic rate of the biosphere.

(The EHAP/Geobiology Seminar Series is jointly hosted by OEB and EPS.)