Co)uniiiiiili/ Concept 403 



of other organisms in its environment but the particular individuals 

 that are dependent upon one another are often not clearly distinguish- 

 able as a unit. In a large community, such as a forest or an oceanic 

 area, the spheres of interaction of many of the members will be much 

 smaller than the area occupied by the whole community. In some 

 instances the limits of a biocenose as a functional entity are fairly 





K'- 





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^ :«k:.: ->. 



Fig. 11.1. Salt marsh community at West Falmouth, Mass., consisting principally 

 of beach grass {Spartina maritima) and fiddler crabs {Uca pugihitor). Various 

 inconspicuous forms are also members of the biocenose. In excavating burrows 

 in the substratum the crabs have rolled balls of mud and sand out onto the 



surface. 



definite and discernible, as is generally ti'ue of an oyster bed, a pond, 

 or a small island. In other instances the activities of members of one 

 community overlap those of another community to such an extent that 

 no specific margins can be set. 



In spite of the difficulties in delimiting communities it is clear that 

 the members of a biocenose share in common the ability to live under 

 the conditions existing in the area and to a greater or lesser extent 

 they are dependent upon one another. Since the community grows, 

 adjusts, and under some circumstances reproduces itself, it represents 



