ABSTRACT
The literal meaning of "thermodynamics" is "heat power" and the subject usually covers several areas of interest to biologists, like chemical equilibria and diffusion of molecules. A biologist may be interested in some local system, e.g., a macromolecule, a test tube of material, a cell. A system which cannot exchange matter or energy with its surroundings is said to be isolated. A universe is thus isolated and a living system is open. The internal energy of that system can be changed by putting it in thermal contact with surroundings which have a higher temperature, causing heat to flow from the surroundings into the system. The First Principle tells us that the energy of the universe remains constant, although that energy may move between the system and surroundings. The Second Principle thus tells us that the universe is acting spontaneously in becoming more disorderly, i.e., increasing disorderliness is the natural direction of the natural evolution of the universe.
