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Nature Favors Extremes: Research Finds Dominance of Large and Small Organisms

Rutgers University researchers have found that the largest and smallest organisms dominate the planet's biomass, according to a study published in the journal PLOS ONE. The study, which involved five years of compiling and analyzing data on the size and biomass of all living organisms on Earth, showed that the pattern of favoring large and small organisms held across all species and was more pronounced in land-based organisms than in marine environments.

Surprising Discovery

Malin Pinsky, an associate professor in the Department of Ecology, Evolution and Natural Resources in the Rutgers School of Environmental and Biological Sciences, and an author of the study, said the conclusion that life on Earth comes packaged predominantly in the largest and smallest sizes was a discovery that surprised them. "Sometimes it seems like mosquitoes or flies or ants must run the world, and yet, when we did the numbers, we found that our world is dominated by the microbes and the trees. These are the silent partners that recycle the nutrients and replenish the air all around us."

Universal Upper Size Limit

Lead author Eden Tekwa, who conducted the research as a postdoctoral fellow at Rutgers and the University of British Columbia, said that the largest body sizes appear across multiple species groups, and their maximum body sizes are all within a relatively narrow range. Trees, grasses, underground fungi, mangroves, corals, fish, and marine mammals all have similar maximum body sizes. "This might suggest that there is a universal upper size limit due to ecological, evolutionary or biophysical limitations," added Tekwa, who is now a research associate with McGill University's Department of Biology.

Humans Belong to Highest Biomass Range

The researchers said humans belong to the size range that comprises the highest biomass, which is a relatively large body size. "Body size is a fundamental feature of life, governing everything from metabolic rates to birth rates and generation times," Pinsky said. "Cataloging which body sizes are most common is a key step towards understanding the world around us."

Implications for Understanding Life Processes

The study's findings provide new insights into elemental life processes and have implications for understanding the ecology, evolution, and biophysics of organisms. The dominance of large and small organisms in the planet's biomass has important implications for the carbon cycle, food webs, and the regulation of Earth's systems.

Possible Future Research

The study opens the door to further research to investigate the ecological, evolutionary, and biophysical constraints on body size and the factors that contribute to the emergence of the patterns observed in the study. It also highlights the need for continued efforts to document and monitor the diversity and distribution of organisms on Earth, particularly in the face of the ongoing biodiversity crisis.

Journal Information: Eden Tekwa et al, The sizes of life, PLOS ONE (2023). DOI: 10.1371/journal.pone.0283020. … journal.pone.0283020
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