SECTION V. ECOLOGY AND EVOLUTION 



INTRODUCTION 



Life shows a general progressive change in 

 time. There is an evolution from a less 

 balanced relationship between the internal 

 and external environment to a more 

 closely adjusted relationship. There is also 

 an evolution from limited control of the en- 

 vironment toward much more control of 

 the external environment. These aspects of 

 ecological evolution parallel the evolution 

 of internal physiological balance and con- 

 trol within the organism. 



What place organic evolution has in cos- 

 mic processes is not clear. Life seems to 

 maintain a dynamic equihbrium of matter 

 and energy (metabolism), which involves 

 chemically complex substances with large 

 molecules such as the proteins and their 

 derivatives. It has been thought that life 

 may retard or temporarily reverse the 

 general increase of entropy or degradation 

 of energy (Breder, 1942a; Schrodinger, 

 1945). Needham (1943), on the other 

 hand, thinks that hving processes conform 

 to the second law of thermodynamics (in- 

 crease of entropy), that thermodynamic 

 order and biological organization are differ- 

 ent, and that both the physical and organic 

 aspects of existence agree in their trend to- 

 ward a more complex organization as free 

 energy becomes less. However, complex or- 

 ganic systems as we know them do not 

 arise in environments with an extremely 

 low energy potential such as the cold sur- 

 faces of the outer planets. The evolution- 

 ary tendency toward an increase in the 

 complexity of organization of Hving systems 

 can only take place within a temperature 

 environment neither too hot nor too cold— 

 roughly that of water in the liquid state 

 (p. 73). 



Lotka (1944, 1945) states that the col- 

 lective activities and effects of organisms 

 indicate a direction of organic evolution to- 

 ward maximal energy intake from the sun, 



598 



and maximal outgo of free energy by dis- 

 sipative processes in living and in decaying 

 dead organisms. In other words, there are 

 evolutionary tendencies toward a higher 

 metabolic rate of the whole ecosystem. 

 "The net effect is to maximize in this sense 

 the energy flux through the system of or- 

 ganic nature." The limits of the evolution- 

 ary increase in energy flux are imposed by 

 the earthly acquisition of the energy out- 

 put of the sun and its ultimate dissipation. 



Although at present the cosmic meaning 

 of these manifestations of Hfe eludes the 

 scientific mind, we can study the changes 

 accompanying evolution and the immediate 

 antecedents of such change. Ecology offers 

 much to the investigation of these prob- 

 lems, especially in the analysis of isolation 

 and adaptation. Other biological sciences, 

 particularly genetics, deal with various evo- 

 lutionary problems. All aspects of biology 

 have been profoundly influenced by evolu- 

 tionary studies and in turn provide evi- 

 dence for analysis of operational factors. A 

 number of recent books summarize modern 

 knowledge of the evolution of living sys- 

 tems (Fisher, 1930; Morgan, 1932; Rob 

 son and Richards, 1936; deBeer, 1938; 

 Huxley, 1940, 1942; Goldschmidt, 1940; 

 Dobzhansky, 1941; Mayr, 1942; Simpson, 

 1944; White, 1945). 



Although ecology is an outgrowth of 

 nineteenth century natural history with its 

 emphasis upon evolution, modern ecologists 

 have been somewhat reticent in developing 

 evolutionary principles. This is surprising, 

 considering the central position of the prob- 

 lem of ecological adaptation in evolution- 

 ary theory. Lamarck and Darwin, in their 

 theories of evolution, regarded adaptation 

 as the main theme, and Wallace came to 

 regard every characteristic of living organ- 

 isms as adaptive. Although some degree of 



