The Concept of Biological Activity and Its Application to Biological Phenomena

Although the life has been a mystery for most physicists since the problem of Maxwell's demon, this mystery is resolved by considering the following characteristics of an organism; the self-reproduction by taking material and energy sources from the outside on the basis of its genetic information, and the selection of self-reproduced organisms to maintain and further improve the genetic information. According to the knowledge of molecular biology revealed recently, the molecular route to accomplish the self-reproduction is evaluated energetically, and a new thermodynamic quantity of biological activity is proposed for characterizing the state of an organism in terms of acquired energy, stored energy and systematization. This quantity is not only compatible with the law of thermodynamics but also reflects the changes in genome and in the mode of gene expression. Thus, the biological activity becomes a useful measure for analyzing various biological phenomena quantitatively. This is illustrated for the large-scale evolution by generating new genes from gene duplication and for the estimation of the energy required for the development of a multicellular organism. The origin of life is also discussed from the aspect of biological activity and the extended view of evolution.