Largest and smallest sizes are dominant in nature

A survey of body sizes of Earth’s organisms conducted by Rutgers University has found that, although life may be found in all shapes and sizes, the most extreme sizes are predominant in nature. The research shows that our planet’s biomass – the material making up all living organisms – is concentrated at either end of the size spectrum.

“This conclusion – that life on Earth comes packaged predominantly in the largest and smallest sizes – was a discovery that surprised us,” said study co-author Malin Pinsky, an associate professor of Ecology, Evolution, and Natural Resources at Rutgers.

“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.”

Over a period of five years, the researchers compiled and analyzed data about the size and biomass of each type of living organism on our planet, ranging from unicellular organisms such as soil archaea and bacteria to large organisms like blue whales or sequoia trees. The analysis revealed that the pattern favoring either large or small organisms can be found in all types of species, although it seems to be more pronounced in land-based organisms.

“The largest body sizes appear across multiple species groups, and their maximum body sizes are all within a relatively narrow range,” said lead author Eden Tekwa, a research associate at McGill University, who conducted the study during a fellowship at Rutgers.

“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.” According to Tekwa, humans belong to the size comprising 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. Cataloging which body sizes are most common is a key step towards understanding the world around us,” Pinsky concluded.

The study is published in the journal PLoS ONE.

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By Andrei Ionescu, Earth.com Staff Writer

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