Maurer, Brian A., and D. R. Brooks. “Energy flow and entropy production in biological systems.” J Ideas 2 (1991): 48-53.
URL1 URL2
Biological systems persist because they process energy and accumulate excesses that are usable in growth and maintenance. There are two general types of energy transformations that occur in biological systems. Heat generating transformations result in lost energy. Conservative energy transformations produce energy that can be stored and used later to do work. Different types of entropy can be associated with each of these types of energetic processes. Heat generating energy transformations occur when energy and entropy flow in opposite directions. Conservative energy transformations are characterized by entropy and energy flowing in the same direction. Thus the system has conflicting tendencies: heat generating processes move it towards unstructured states and conservative processes move it towards complex structured states. Both tendencies increase the entropy of the system. These ideas are examined from the viewpoint of energy flow through organisms and populations of organisms. As entropy and energy flow through such systems at different rates, structure accumulates at any given biological level, and that structure is constrained by energy and entropy flows at other levels of organization. Rate gradients in entropy production lead to different types of constraint systems governing hierarchically related entities and to the generation of historical constraints at any given level of organization.