Supply–demand balance and metabolic scaling
- *Department of Physics, 104 Davey Laboratory, Pennsylvania State University, University Park, PA 16802; †Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, CA 93106; §International School for Advanced Studies (S.I.S.S.A.), Via Beirut 2-4, 34014 Trieste, Italy;¶ Istituto Nazionale di Fisica della Materia and the Abdus Salam International Center for Theoretical Physics, 34100 Trieste, Italy; and ∥Dipartimento di Ingegneria Idraulica, Marittima e Geotecnica, Universitá di Padova, I-35131 Padova, Italy
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Edited by Simon A. Levin, Princeton University, Princeton, NJ, and approved June 13, 2002 (received for review April 10, 2002)
Abstract
It is widely accepted that metabolic rates scale across species approximately as the 3/4 power of mass in most if not all groups of organisms. Metabolic demand per unit mass thus decreases as body mass increases. Metabolic rates reflect both the ability of the organism's transport system to deliver metabolites to the tissues and the rate at which the tissues use them. We show that the ubiquitous 3/4 power law for interspecific metabolic scaling arises from simple, general geometric properties of transportation networks constrained to function in biological organisms. The 3/4 exponent and other observed scaling relationships follow when mass-specific metabolic demands match the changing delivery capacities of the network at different body sizes. Deviation from the 3/4 exponent suggests either inefficiency or compensating physiological mechanisms. Our conclusions are based on general arguments incorporating the minimum of biological detail and should therefore apply to the widest range of organisms.
Footnotes
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↵ ‡ To whom reprint requests should be addressed. E-mail: damuth{at}lifesci.ucsb.edu.
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This paper was submitted directly (Track II) to the PNAS office.
- Copyright © 2002, The National Academy of Sciences
