Figure 3. The mean slopeb and metabolic level (L ) ± standard deviation in water- (A ) and (B ) air-breathing species at minimal (in green) and maximal activity (purple). L values are adjusted to 20 ℃ for comparison (see Appendix S8). Dash-dotted lines show the expected relationship between b and L , if muscular work scales asm1 , and gradually increases L by an order of magnitude from minimal activity (eq. [S7]). Species’ data are shown to illustrate variation, with a line joining each pair of measurements, i.e., at minimal and maximal activity for single species. Mean values were used when more than one pair of measurements was available for a species. Dashed horizontal lines indicate the typical boundaries proposed by the MLBH.