CHAPTER 2 



COMMUNITY FUNCTIONS— THE DYNAMICS OF THE 

 BIOTIC FORMATION 



THE BIOME AS A SOCIAL ORGANISM 



Introduction. The biome or plant-animal formation is the basic 

 community unit; that is, two separate communities, plant and animal, 

 do not exist in the same area. The sum of plants in the biome has 

 long been known as vegetation, but for animals no similar distinc- 

 tive term has become current. It is obvious, however, that the two 

 do not represent natural divisions of the biotic complex. The plant- 

 animal formation is composed of a plant matrix with the total number 

 of included animals, of which the larger and more influent species may 

 range over the entire area of the biome, including its subdivisions and 

 developmental stages. 



The extent and character of the biome are exemplified in the 

 great landscape types of vegetation with their accompanying animals, 

 such as grassland or steppe, tundra, desert, coniferous forest, decidu- 

 ous forest, and the like. These commonly represent biotic formations 

 or climaxes, which in their general features have been noted by natu- 

 ralists since the early days of biology. Each of these consists of a 

 great biotic complex of fully developed and developing communities. 

 The mature mass is the final expression of the response of communi- 

 ties to climate. 



The term biome, as here employed, is regarded as the exact 

 synonym of formation and climax when these are used in the biotic 

 sense. 



Nature of the Biotic Formation. The concept of the biome is a 

 logical outcome of the treatment of the plant community as a complex 

 organism, or superorganism, with characteristic development and 

 structure. As such a social organism, it was considered to possess 

 characteristics, powers, and potentialities not belonging to any of its 

 constituents or parts. 



As indicated in the previous chapter, the recognition of the fact 

 that the plant and animal community are generally coextensive natu- 



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