CHAPTER V 



THE EVOLUTION OF ANIMAL 

 COMMUNITIES 



I 



F, AS has been suggested 

 earlier in this discussion, animal communities 

 show similarities to organisms, then we should 

 expect to be able to discover differences in the 

 communities that occupy the same habitat as 

 time passes; in other words there should be some 

 sort of community evolution which would run 

 from pioneer communities in which the habitat is 

 being penetrated for the first time by animal life, 

 to mature communities, usually called climax 

 communities, in which community life has be- 

 come stable. Such evolutions should take place 

 fairly rapidly. Beyond these there should be the 

 changes brought on by the slow shifting of cli- 

 mates such as have produced a desert in south- 

 western United States in an area where forests 

 once grew and where fossil trees are still to be 

 found. 



In nature even fairly rapid community evolu- 

 tion is usually too slow to be observed in the 

 life of a single individual; fortunately all are not 



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