Entropy and Information in Biology

Abstract

"Animals have genes for altruism, and those genes have been selected in the evolution of many creatures because of the advantage they confer for the continuing survival of the species."-Lewis Thomas Summary With the work of Leo Szilárd and Claude Shannon, we now realize that the information stored in a life system can be measured, and that the loss of that information produces entropy. In fact, there is a universality to open systems having an energy flow through them, making internal ordering a natural process, including evolution of new structures and principles derived from optimization. 12.1 Defining Information Most people have a good sense of the what information is. But few know that information can be measured by a number. From our sense about information, we recognize that life systems act to preserve and develop information. At the molecular level, the information necessary for life activity and replication is stored in macromolecules. For life on Earth, this information is coded in the arrangement of the base-pair sequences in deoxyribonucleic acid (DNA) and in ribonucleic acid (RNA). We know from the statistical basis of thermodynamics that an organism is an open system which takes in energy with a degree of order, maintains and builds structures (which necessarily increases local order), and expels heat energy and waste material to the environment, resulting in an increase in the disorder of the environment. Part of the work of higher level organisms is to use the flow of energy to build information, such as new DNA or memories. The story of how information can be measured began when James Clerk Maxwell was thinking about the entropy of an ideal gas. He imagined a small door in a partition put halfway through the volume of gas. The door would be operated by © Springer Nature Switzerland AG 2020 W. C. Parke, Biophysics, https://doi.