Living Things Are Unique Thermodynamic Systems
Questions arise frequently about whether living organisms obey the laws of thermodynamics. The short answer is that they most deÞnitely do. Most classical treatments of thermodynamics deal with closed systems at equilibrium. A closed system can exchange energy, but not matter, with its surroundings.
A living organism is obviously not a closed system, but an open system that can exchange both matter and energy with its surroundings. Because living organisms are open systems, they cannot be at equilibrium as long as they are alive, as shown in the following figure. They can, however, achieve a steady state, which is a stable condition. It is the state in which living things can operate at maximum thermodynamic efficiency. This point was established by Ilya Prigogine, winner of the 1977 Nobel Prize in chemistry for his work on nonequilibrium thermodynamics. He showed that for systems not at equilibrium, ordered structures can arise from disordered ones. This treatment of thermodynam-ics is quite advanced and highly mathematical, but the results are more directly applicable to biological systems than those of classical thermodynamics. This approach applies not only to liv-ing organisms but to the growth of cities and to predictions of auto traffic.