In treating the living organism as a whole, as a system, rather than simply as a set of components together with relationships between components, von Bertalanffy drew attention to the important distinction between systems which are open to their environment and those which are closed. He defined an open system (1940) as one having import and export of material. More generally, between an open system and its environment there may be exchange of materials, energy, and information. Organisms, he pointed out, are unlike closed systems in which unchanging components settle in a state of equilibrium; organisms can achieve a steady state which depends upon continuous exchanges with an environment. What is more, the steady state may be thermodynamically unlikely, creating and/or maintaining a high degree of order, where closed systems have no path to travel but that towards increasing disorder (high entropy). In a hierarchy of systems such as that represented by the sequence from cell organelle to organism, or, in general, in any hierarchy of open systems, maintenance of the hierarchy will entail a set of processes in which there is communication of information for purposes of regulation or control.
(Checkland, 1981, p. 82f)