FROM the tiniest bacterium to the largest tree or mammal, most of life on Earth seems to favour the same, optimum metabolic rate.
Within groups of organisms, smaller species have faster metabolisms, producing more energy per cell than larger ones. But when at the Petersburg Nuclear Physics Institute in Russia and colleagues looked at the whole range of life, they found no overall relationship between size and metabolic rate (Proceedings of the National Academy of Sciences, ).
While body mass varied by up to 20 orders of magnitude, metabolic rate varied by a mere factor of 10,000. Because most organisms鈥� metabolisms were clustered between 1 and 10 watts per kilogram of mass, Makarieva says there may be an optimum metabolic rate that lies within this range. 鈥淥rganisms that lie close to this value may be the fittest.鈥�
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