Fig. 3.

Growth and metabolism size class scaling. In A and B, original data from Fig. 1 A and C are binned into logarithmic body size classes to highlight the principal relationships and give equal representation to different size classes. Exponents and 95% CIs are shown to the right of each plot for the nonbinned data, with filled circles for metabolism (above) and empty circles for growth (below). (A) Scaling relationships for basal metabolism (W) and maximum growth (g/s) from Fig. 1 A and C (with additional taxonomic groups) reveal scaling similarities for most groups but a systematic divergence at larger body mass across groups. (B) Mammal scaling relationships for metabolism across activity levels and maximum growth across life stages shows the boundaries in which these characteristics vary. (C) The prevailing view is that metabolism determines growth scaling (orange arrows of causality) on the basis that within a given major group, both variables scale as k ∼ 3/4 (parallel thick lines). The metabolic view, however, cannot explain why growth follows the same universal k ∼ 3/4 scaling both within and across groups, given that metabolism often shows shifts in elevation between groups. A more parsimonious view is that across groups, metabolism adheres to isometric bounds (k ∼ 1), but that within major groups, metabolism adjusts to growth scaling of k ∼ 3/4 (blue arrows of causality).