The Organization of Matter and Life 34i 



orderliness. Other inter-specific relationships such as competitive 

 coexistence are caused and maintained by the similar ecological 

 tolerances of different species and result in an increase of the num- 

 ber of different species in any one organizational or trophic level, 

 which is another phase of randomness. It is a peculiar property 

 of these systems that the more complex the prey-predator levels 

 become, the larger is the number of potentially competing species 

 that can coexist. This phenomenon arises from several mecha- 

 nisms and is an expression of increased ecological stability. 



Although each evolutionary process in community evolution is 

 in itself fairly simple, the effect of these processes brings about 

 a highly complex and dynamic situation. If, for example, one of 

 two competing species in a community evolves into a predator 

 of the other species, this change would lessen the competitive 

 selection pressures acting on the second species and increase the 

 selection pressures associated with being preyed upon. If other 

 predators were already present, the newly evolved predator would 

 enter into a competitive relationship with them. The increase in 

 number of predators might lead to the evolution of food specializa- 

 tions among them, such as the divergence between dogs, cats, and 

 shrews. This is the mechanism of adaptive radiation. It is an in- 

 crease in randomness in producing more ecological types of organ- 

 isms but is an increase in orderliness in reducing the number of 

 species belonging to any one of these ecological types. These exam- 

 ples are a few of many kinds of processes showing that every change 

 in relationships within the community or in the relative success of 

 any species brings about changes in the details of selection pressures 

 acting on many other species in the community. Thus change in 

 itself produces a reorientation of the specific paths of evolution 

 which originally caused the change. 



Concurrently with splitting or congregating species, the geo- 

 tectonic factor splits and congregates the communities of which 

 the species are a part. The splitting of communities is in the direc- 

 tion of randomizing by means of increasing the number of differ- 

 ent kinds of communities. However, the congregating action of 

 the geotectonic factor results in the emergence of still another 

 kind of order typified by the biome. Because of competitive ad- 

 vantages, certain organisms become the dominant ones in the com- 

 munity. These dominants superimpose peculiar ecological prop- 

 erties on the over-all climatic and edaphic characteristics of the 

 area, such as the shade pattern in an evergreen coniferous forest. 

 When daughter communities are formed by the splitting of parental 



