Recent research provides an unprecedented account of the diversity and biomass of life on Earth, but the data also suggest unexplained patterns such as the dominance of very different taxa. We compile body size biomass spectra across all taxa to qualitatively test three hypotheses based on metabolic food web interactions, macroevolution, and the evolution of multicellularity.
Results/Conclusions
We find that small (10-14 g) and large (106 g) organisms vastly outweigh other sizes. The global spectrum reveals an allometric power exponent of 0.06±0.007 (S.D.), which is compatible with some metabolic food web predictions. However, the dominant pattern consists of isolated size modes that suggests a role for multicellularity. The data and theory provide a comprehensive snapshot of life and point to a size-based synthesis of microevolution and macroecology.