EVOLUTION OF INTERSPECIES INTEGRATION AND ECOSYSTEM 



729 



suits in a biotic system that may appro- 

 priately be called an interspecies supraor- 

 ganism. The incorporation and control of 

 the physical habitat by the interspecies 

 supraorganism produces a unitary ecosys- 

 tem. Homeostatic equilibrium within the 

 ecosystem (balance of nature) is in large 

 part the result of evolution. 



CONCLUSION OF SECTION V 

 ON ECOLOGY AND EVOLUTION 



Ecology contributes important facts and 

 principles to the general theory of evolu- 

 tion. In particular, the environmental 

 influences on hereditary variation, the role 

 of reproductive isolation, and the origin and 

 maintenance of adaptation through natural 

 selection are prime subjects of ecological 

 investigation, shared in part with other 

 fields of biology. 



Evolution gives an essential perspective 

 to our view of the organism, the species, 

 and the community. It adds a diflEerent 

 time dimension to the ontogenetic dimen- 

 sion (also time) and to the spatial dimen- 

 sions. Many facts may be arranged in an 

 order along this evolutionary dimension 

 that could not be detected through the 

 study of the ecological relations of existing 

 species and their developmental stages. We 

 should be aware, however, that the con- 

 sideration of evolutionary phases of ecology 

 introduces difficulties of scientific method 

 and interpretation not met in dealing 

 with the descriptions and analysis of exist- 

 ing community structure and function. 

 Sometimes our conclusions rest upon cir- 

 cumstantial evidence of events that hap- 

 pened many millions of years ago and left 

 only vague traces of their occurrence. 



The analytic study of the parts of a 

 system, and the synthetic study of the 

 whole system, are both necessary, and 

 each is inadequate without the other. Lotka 

 (1945) has emphasized the necessity of 

 envisaging the evolving system as a whole 

 —the aggregate of past and present coexist- 

 ing species in their inorganic and organic 

 environment— for any adequate treatment of 

 evolution. 



Through the action of the habitat upon 

 living systems, the reaction of these upon 

 the environment often resulting in an or- 

 ganic evolution of the physical environment, 

 and the coaction between organismic units 

 of various levels of integration upon each 



other, we find that fife and habitat are in- 

 tegrated into an evolving ecosystem (Egler, 

 1942), ultimately incorporating the entire 

 biosphere of the earth (Vemadski, 1929, 

 1945). The unity of the biosphere is the 

 resultant of the complex interaction of many 

 factors- a complexity so great that many 

 competent biologists have failed to recog- 

 nize the existence of the unitary whole. 

 Our attempts to analyze and synthesize the 

 ecological aspects of the biosphere are 

 necessarily superficial; the principles that 

 emerge at this stage of our knowledge are 

 often out of perspective, overemphasized, 

 and oversimplified. 



"I have often thought," wrote Liebig to 

 his friend Duclaux, "in my long and prac- 

 tical career and at my age [69 years] how 

 much pains and how many researches are 

 necessary to probe to the depths a rather 

 complicated phenomenon. The greatest dif- 

 ficulty comes from the fact that we are too 

 much accustomed to attribute to a single 

 cause that which is the product of several, 

 and the majority of our controversies come 

 from that." 



Oversimpfification is an error often com- 

 mitted by scientists in their drive to dis- 

 cover basic principles that relate diverse 

 facts. If the terms are general enough to 

 incorporate complex phenomena, they are 

 likely to be hazy and ambiguous. Neverthe- 

 less, on occasion fundamental principles 

 may be stated in language that has mean- 

 ing to most readers and in a manner that 

 brings order to vast accumulations of 

 knowledge. 



We may thus stmimarize the section on 

 Ecology and Evolution— and indeed the 

 book as a whole— by repeating a principle 

 discussed by Leake (1945): The prob- 

 ability of survival of individual living 

 things, or of populations, increases with the 

 degree with which they harmoniously ad- 

 just themselves to each other and their en- 

 vironment. This principle is basic to the 

 concept of the balance of nature, orders the 

 subject matter of ecology and evolution, 

 underlies organismic and developmental 

 biology, and is the foundation for all 

 sociology. 



Principles that assort facts in meaningful 

 order have not fulfilled their purpose un- 

 less they stimulate further fact finding, 

 further discovery of relationships, further 

 synthesis, and ultimately contribute to the 

 evolution of human wisdom. 



