title: Towards a definition of life.
abstract: This article offers a new definition of life as a "self-contained, self-regulating, self-organizing, self-reproducing, interconnected, open thermodynamic network of component parts which performs work, existing in a complex regime which combines stability and adaptability in the phase transition between order and chaos, as a plant, animal, fungus, or microbe." Open thermodynamic networks, which create and maintain order and are used by all organisms to perform work, import energy from and export entropy into the environment. Intra- and extracellular interconnected networks also confer order. Although life obeys the laws of physics and chemistry, the design of living organisms is not determined by these laws, but by Darwinian selection of the fittest designs. Over a short range of normalized energy consumption, open thermodynamic systems change from deeply ordered to chaotic, and life is found in this phase transition, where a dynamic balance between stability and adaptability allows for homeokinesis. Organisms and cells move within the phase transition with changes in metabolic rate. Seeds, spores and cryo-preserved tissue are well within the ordered regime, while health probably cannot be maintained with displacements into the chaotic regime. Understanding life in these terms may provide new insights into what constitutes health and lead to new theories of disease.
authors.affiliation: Meakins Christie Laboratories, Montreal Chest Institute, McGill University Health Centre Research Institute, Montreal. peter.macklem@mcgill.ca
authors.forename: Peter T
authors.initials: PT
authors.lastname: Macklem
authors.forename: Andrew
authors.initials: A
authors.lastname: Seely
mesh_terms: D002453:Cell Cycle; D022082:Cellular Structures; D055598:Chemical Phenomena; D019277:Entropy; D006801:Humans; D019369:Life; D055585:Physical Phenomena; D013816:Thermodynamics