REFERENCE:Schneider, E.D, Kay, J.J., 1995, "Order from Disorder: The Thermodynamics of Complexity inBiology", in Michael P. Murphy, Luke A.J. O'Neill (ed), "What is Life: The Next Fifty Years.Reflections on the Future of Biology", Cambridge University Press, pp. 161-172Order from Disorder: The Thermodynamics of Complexity in BiologyEric D. Schneider and James J. Kay© COPYRIGHT 1995 Table of Contents Introduction1.Thermodynamic Preliminaries2.Dissipative Systems3.Living Systems as Gradient Dissipators4.A Thermodynamic Analysis of Ecosystems5.Order from DISORDER and order from order6.References7.IntroductionIn the middle of the nineteenth century, two major scientific theories emerged about the evolution ofnatural systems over time. Thermodynamics, as refined by Boltzmann, viewed nature as decayingtoward a certain death of random disorder in accordance with the second law of thermodynamics. Thisequilibrium seeking, pessimistic view of the evolution of natural systems is contrasted with theparadigm associated with Darwin, of increasing complexity, specialization, and organization ofbiological systems through time. The phenomenology of many natural systems shows that much of theworld is inhabited by nonequilibrium coherent structures, such as convection cells, autocatalyticchemical reactions and life itself. Living systems exhibit a march away from disorder and equilibrium,into highly organized structures that exist some distance from equilibrium.This dilemma motivated Erwin Schrödinger, and in his seminal book What is Life? (Schrödinger, 1944),he attempted to draw together the fundamental processes of biology and the sciences of physics andchemistry. He noted that life was comprised of two fundamental processes; one "order from order" andthe other "order from disorder". He observed that the gene generated order from order in a species, that is, the progeny inherited the traits of the parent. Over a decade later Watson and Crick (1953)provided biology with a research agenda that has lead to some of the most important findings of the lastfifty years.However, Schrödinger's equally important but less understood observation was his order from disorderpremise. This was an effort to link biology with the fundamental theorems of thermodynamics(Schneider, 1987). He noted that living systems seem to defy the second law of thermodynamics whichinsists that, within closed systems, the entropy of a system should be maximized. Living systems,however, are the antithesis of such disorder. They display marvelous levels of order created fromdisorder. For instance, plants are highly ordered structures, which are synthesized from disorderedatoms and molecules found in atmospheric gases and soils.Schrödinger solved this dilemma by turning to nonequilibrium thermodynamics. He recognized thatliving systems exist in a world of energy and material fluxes. An organism stays alive in its highlyorganized state by taking high quality energy from outside itself and processing it to produce, withinitself, a more organized state. Life is a far from equilibrium system that maintains its local level oforganization at the expense of the larger global entropy budget. He proposed that the study of livingsystems from a nonequilibrium perspective would reconcile biological self-organization andthermodynamics. Furthermore he expected that such a study would yield new principles of physics.This paper examines the order from disorder research program proposed by Schrödinger and expandon his thermodynamic view of life. We explain that the second law of thermodynamics is not animpediment to the understanding of life but rather is necessary for a complete description of livingprocesses. We expand thermodynamics into the causality of the living process and show that the secondlaw underlies processes of self-organization and determines the direction of many of the processesobserved in the development of living systems.Thermodynamic Preliminaries Thermodynamics has been shown to apply to all work and energy systems including the classictemperature-volume-pressure systems, chemical kinetic systems, electromagnetic and quantum systems.Thermodynamics can be viewed as addressing the behaviour of systems in three different situations: 1)equilibrium, (classical thermodynamics), i.e. the actions of large numbers of molecules in a closedsystem, 2) systems that are some distance from equilibrium, and will return to equilibrium, i.e.molecules in two flasks connected with a closed stopcock; one flask holds more molecules than theother and upon opening the stopcock the system will come to its equilibrium state of an equal number ofmolecules in each flask, and 3) systems that have been moved away from equilibrium and areconstrained by gradients to be at some distance from the equilibrium state, ie. two connected flasks witha pressure gradient holding more molecules in one flask than the other.Exergy is a central concept in our discussion of order from disorder. As already mentioned, energy varies in its quality or capacity to do useful work. During any chemical or physical process the qualityor capacity of energy to perform work is irretrievably lost. Exergy is a measure of the maximumcapacity of an energy system to perform useful work as it proceeds to equilibrium with its surroundings(Brzustowski & Golem, 1978, Ahern, 1980).The first law of thermodynamics arose from efforts to understand the relation between heat and work.The first law says that energy cannot be created or destroyed and that the total energy within a closed orisolated system remains unchanged. However, the quality of the energy in the system (i.e the exergycontent) may change. The second law of thermodynamics requires that if there are any processesunderway in the system, the quality of the energy (the exergy) in that system will degrade. The secondlaw can also be stated in terms of the quantitative measure of irreversibility, entropy, which for anyprocess is greater than zero. The second law can also be stated as: any real process can only proceed in adirection which results in an entropy increase.In 1908 thermodynamics was moved a step forward by the work of Carathéodory (Kestin, 1976) whenhe developed a proof that showed that the law of "entropy increase" is not the general statement of thesecond law. The more encompassing statement of the second law of thermodynamics is that "In theneighbourhood of any given state of any closed system, there exists states which