Chapter 12
Entropy and Information in Biology
“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 half-way through the volume of gas. The door would be operated by
© Springer Nature Switzerland AG 2020
W. C. Parke, Biophysics, https://doi.org/10.1007/978-3-030-44146-3_12
543
Entropy and Information in Biology
“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 half-way through the volume of gas. The door would be operated by
© Springer Nature Switzerland AG 2020
W. C. Parke, Biophysics, https://doi.org/10.1007/978-3-030-44146-3_12
543