Book Reviewed: Entropy Principle for the Development of Complex Biotic Systems: Organisms, Ecosystems, the Earth, by Ichiro Aoki

Entropy and the flow of nature

The title of this book is a little puzzling, since I thought the author would be discussing about the application of the second law of thermodynamics; the concept of entropy, the operation of the biological equivalent of Maxwell’s Demon (the perpetual motion machines), information theory (Shannon’s entropy) and statistical mechanics to explain the high-degree of order in biological processes of a living cell. But this is not what you find in this book. This book is about the energy budget equation applied to macroscopic systems like animals, plants and the ecosystems. The energy budget equation has been used in meteorology and global climatology, which is based on both first and second laws of thermodynamics. In this book, the author describes the results of his calculation for the entropy production for a plant, human, lizard, deer, hog, earth, solar system and an ecosystem.

Thermodynamics is robust science because it is non-reductionistic. This means that the general scheme of systems does not depend on the detailed chemical properties of constituent subsystems and sub-subsystems but only to micro configurations (particles), thermodynamic parameters (pressure, temperature, volume, entropy, etc.) and statistics. For example, entropy is a measure of the quality (usefulness) of energy: the higher the entropy, the lower the quality (less useful) of energy. Also, it is a measure of the randomness or disorder. In a closed system such as this universe, entropy cannot decrease, but in an open system like a living cell, planets, stars, and galaxies, irreversible reactions dominate. The second law states that the change of entropy production for an irreversible process is always larger than the corresponding reversible process. And in the latter, change in entropy production is always zero. Entropy production is a measure of the strength and magnitude of the irreversibility of a processes and pertains to process of energy flow and the transportation of matter.

For example for earth-sun system, of the ~340 W/m² of solar radiation received by the earth (fixed by Earth-Sun distance), an average of ~77 W/m² is reflected back to space by clouds and atmosphere, and ~23 W/m² is reflected by earth’s surface albedo, leaving ~240 W/m² of solar energy input to the Earth's energy budget. But earth’s surface radiates about 17 percent of incoming solar energy as thermal infrared energy; 12 percent of it escapes to outer space, and the rest 5% become trapped by greenhouse gases like water vapor, carbon dioxide, methane raising the planets’ temperature.