Biological and Biogeochemical Preludes to the Ediacaran Radiation

Abstract

Evolution is sometimes envisioned as a dynamic process played out on an inert or passive planetary platform; however, if the geological record contains a message for evolutionary biology, other than the fact of the fossil record itself, it is that the Earth's surface is in a continual state of change. On various time scales, climates fluctuate, reservoirs and fluxes of biogeochemical cycles vary, sea levels rise and fall, and oceanic water masses form and decay, while continents grow, split apart, drift, and recombine. At the same time, organisms that compete with, prey upon, provide food for, or live in symbiotic association with any given taxon of interest radiate, undergo morphological and physiological change, and become extinct. This is the context of evolution, and paleontological efforts to understand evolutionary events of the past require that we attempt to root those events in the context of ongoing biological and environmental change.