Figure 2
Temperature-regulated basal metabolic rate (BMC) (watts) and brain size (gram). A. Allometric relationships between basal metabolic rate (BMR) (watts) and body mass (gram) for the endotherms (including 525 mammals [43] and 320 birds [37],[42]) (plotted in red triangles) and the ectotherms (including 265 fishes [37],[42],[44], 155 reptiles [37],[42] and 158 amphibians [37],[42]) (plotted in black open circles). The BMR versus body mass data were well fit by the equation 0.0305×0.682 (adjusted-R2 = 0.933, p < 0.01) for the endotherms and by 0.00525×0.81 (adjusted- R2 = 0.91, p < 0.01) for the ectotherms. The datasets are given in Additional file 3: Table S3. All the data plotted here for ectotherms were normalized to the temperature of 16°C, and the data for the endotherms were normalized to 38°C based on Eq. (2) (see also the methods in references [28],[37]) to minimize the errors induced by measuring temperatures. B. When the metabolic rate data for the endotherms were normalized to 16°C, they merged into the group of ectothermic metabolic data. However, there some difference between these groups remained, particularly for the small animals. C. The BMR ratios as a function of body size for the endotherms to ectotherms was BMRendotherm(38°C)/BMRectotherm (16°C) (plotted in red line) and BMRendotherm(16°C)/BMRectotherm (16°C) (blue line). D. The brain masses (grams) as a function of body BMRs (watts) for the ectotherms (black line) and endotherms (red line) were based on the fit equations in Figures 1A and 2A.