BIOLOGICAL ORDER AND ENTROPY 



Reproduction as well as maintenance involves a degradation of 

 energy. But during reproduction two organisms have been pro- 

 duced out of one. Order has increased. 



Entrop\' is a measure of atomic disorder. An increase of disorder 

 corresponds to an increase of entropy, and an increase of order 

 to a decrease of entropy. As our subject is biological order, we 

 have to consider the production or reproduction of order in its 

 most general aspect, namely, from a thermodynamical viewpoint. 



Entropy 



Physicists know that every isolated system changes in such a 

 way as to approach a definite state of rest. This state of rest is a 

 state of equilibrium. It corresponds not to a loss but to a deg- 

 radation of energy. The entropic change during such an 

 irreversible process is the difference between the entropy at the 

 end and the entropy at the beginning. The measure of entropy is 

 a measure of a difference between an initial and a final state. 



The value of entropy is given by the formula: 



Entropy = k log D 



where k is the Boltzmann constant and D is the measure of the 

 atomic disorder. The state of rest which an isolated system tends 

 to reach corresponds to a maximum entropy, that is, to a maximum 

 disorder. 



Now entropy, being a measure of disorder, is related to proba- 

 bility. In a closed system evolving from a less probable to a more 

 probable state, the probability increases, and so does entropy. The 

 relation between entropy and probability is given by the Boltzmann- 

 Planck formula: 



S- k In P 



where S is the entropy, k the Boltzmann constant expressed in 

 ergs per degree centigrade, that is, 1.38 X 10" ^'^ and P the number 

 of "elementary complexions." "Elementary complexions" corre- 

 spond to the "discrete configurations," that is, to the jumps of the 

 atomic system from one metastable structure to another. 



[89] 



