NSF Award Abstract - #0202180

AWSFL008-DS3

Universal Scaling Laws in Biology: Origins, Applications, and Ramifications

Abstract

Life is the most complex physical phenomenon in the universe, manifesting an extraordinary diversity of form and function over an enormous scale ranging from the largest animals and plants to the smallest microbes and sub-cellular units. Yet, many of its most fundamental and complex phenomena scale with size in a surprisingly simple fashion. For example, metabolic rate (the power needed to sustain life) scales as the 3/4-power of mass over 27 orders of magnitude ranging from molecular and intra-cellular levels up through the smallest unicellular bacteria to the largest multicellular organisms. Similarly, time-scales (such as lifespan and growth-rate) and sizes (such as genome length and density of mitochondria) scale with exponents that are typically simple powers of 1/4. The universality and simplicity of these scaling relationships suggest that fundamental universal principles underlay much of the generic structure, function and organization of many biological phenomena.

The premise of this project is that regardless of size, almost all life is sustained, and ultimately constrained, by space-filling, fractal-like hierarchical branching networks (both real and virtual), which are optimized by the forces of natural selection. Previous work has shown how these principles explain universal quarter-power scaling and how they lead to a quantitative understanding of many diverse biological systems. This project will continue to explore and elaborate on these universal principles by applying them to other fundamental problems in biology while extending the paradigm into other areas of science where their analogs might be applicable, such as corporate structures and urban development. The biological problems will include aging and mortality, minimum and maximum sizes of mammals, size and energy distributions in ecosystems, quantifying evolution including thermodynamic considerations, and understanding the scaling of genome size and its relationship to the complexity of the organism.