Recasting thermodynamics to inherently include a living system's environment at multiple scales.
Roydon, FRASER*,1, James, KAY1, 1 University of Waterloo, Waterloo, Ontario, CANADA
ABSTRACT- Prigogine′s famous dissipative structures and local viewpoint of entropy production inherently provides a theoretical framework less than ideally suited for studying self-organizing, self-replicating, hierarchal, adaptive systems. Thermodynamically, Prigogine′s approach represents a system-centric (or open-system) thermodynamic view of biological and ecological systems. Unfortunately, the open-system viewpoint de-emphasizes the extremely important ecological consideration of a living system′s environment. Furthermore, Prigogine′s focus on local equilibrium and entropy has lead to conceptual slip-ups by others. For example, in many discussions of Prigogine′s work it is incorrectly assumed that a increase in dissipation (entropy production) is necessarily coupled to an increase in energy flux. This observation reveals that the clear distinction between energy magnitude and energy quality that exists is not well appreciated by many. In this work it is proposed that it would be more productive to characterize ecosystems from the basis of an isolated-system (or exergy) thermodynamic viewpoint which leads, for example, to the ideas of degradation structures and generalized exergy. One result of the degradation structure viewpoint is that the number and type of thermodynamic gradients can theoretically be used to distinguish between, and quantify, thermodynamic complexity and complicatedness. Defining complexity as being proportional to the number of distinctly different accessible thermodynamic gradients inherently considers the multi-scale reach of an ecosystem or organism as it attempts to adapt to and survive in its environment. In addition, the generalized exergy concept provides a means to quantify and hence characterize far from equilibrium living systems. For example, intrinsic exergy can be used to define a thermodynamic based, hierarchal structure dependent on an ecosystem′s or organism′s distance from thermodynamic equilibrium, while exergy destruction rates can provide a measure of the ability of a living system to utilize energy. In conclusion, the isolated-system viewpoint coupled with the concepts of generalized exergy and degradation structures would seem to offer a useful framework for characterizing the dynamics and structure of ecosystems.
Key words: exergy, degradation structures, complexity
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