ABSTRACT
Among a vast range of species from microorganisms to the largest mammals, many biological variables seem to bear a specific quarter-power scaling relationship to overall body size (Fig. 9.1). For example, various biological times (e.g., lifespan and the time between heartbeats) scale with body mass to the 1/4 power, and resting metabolic rate scales with body mass to the 3/4 power (McMahon, 1973; Calder, 1996; Schmidt-Nielsen, 1984; Niklas, 1994; Enquist et al., 1998, 1999; Brown and West, 2000; Niklas and Enquist, 2001). Several attempts have been recently made to derive such general allometric scaling laws based on maximum efficiency (West et al., 1997, 1999b; Banavar et al., 1999) that has been regarded as the fundamental design principle for biological systems. Andresen et al. (2002) argued that maximum efficiency built on evolutionary as well as thermodynamic grounds (Dewey and Delle Donne, 1998) may suffer from internal inconsistencies when it is used to explain scaling laws.
