Biological scaling and physics

Kleiber’s law in biology states that the specific metabolic rate (metabolic rate per unit mass) scales as M^-1/2 in terms of the massM of the organism. A long-standing puzzle is the (-1/4) power in place of the usual expectation of (-1/3) based on the surface to volume ratio in three-dimensions. While recent papers by physicists have focused exclusively on geometry in attempting to explain the puzzle, we consider here a specific law of physics that governs fluid flow to show how the (-1/4) power arises under certain conditions. More generally, such a line of approach that identifies a specific physical law as involved and then examines the implications of a power law may illuminate better the role of physics in biology.