A system that exchanges energy, information and matter with its environment and thus one that disobeys the second law of thermodynamics. There are two types of open systems:
•simple system: consists of few elements or degrees of freedom and can only show linear (quantitative) change. There is a one-to-one or proportional relationship between input and output in such a system
•complex system: consists of many elements and can show non-linear (qualitative) change under certain conditions. There is no one-to-one relationship between input and output and the system may change abruptly from state to another. A complex open system has two contributions to its total entropy: positive entropy (due to irreversible processes within the system) and negative entropy (due to the exchange of energy, information and matter with the surround). When positive entropy exceeds negative entropy, the system is irreversibly drawn to the equilibrium point of maximum entropy. With the infusion of more external energy, the system may suddenly jump to a new far-from-equilibrium state, which then takes control over the system’s dynamics. The distinction between open and closed is not categorical as no system is completely open, which would make it impossible to define its boundaries. Certainly, some species are more closed (viz., the ‘specialists’) than others (viz., the ‘generalists’) in that they are only open to a restricted ecological niche.
See Classical thermodynamics, Closed system, Complex system, Complexity, Cybernetics, Degrees of freedom (or Bernstein’s) problem, Dissipative system, Downward causation (or macrocausation), Dynamical systems approaches, Emergence, Energy, Entropy, Equifinality, First law of thermodynamics, General systems theory (GST), Hydraulics, Information, Levels of organization, Matter, Order parameter, Quantitative and qualitative change, Second law of thermodynamics, System