402 The Community 



harmful action. Mutual tolerance and beneficial interaction have 

 brought about a certain degree of integration within the group. Such 

 a group of mutually adjusted plants and animals inhabiting a natural 

 area is known as a community. 



Since the word community is employed in common parlance in 

 many senses as well as in the specific sense described above, consid- 

 erable ambiguity is apt to result. Accordingly it is often desirable to 

 use the term biocenose—a. shortened form of the word "biocoenosis" 

 coined in 1880 by Mobius— to distinguish the special meaning attached 

 to the community concept by ecologists. In explaining his proposed 

 term Mobius used an oyster-bed community as an example. Since 

 his statement is of considerable interest as a landmark in the develop- 

 ment of ecological thought, an excerpt from it is quoted. 



Every oyster-bed is thus, to a certain degree, a community of living 

 beings, a collection of species and a massing of individuals, which find 

 here everything necessary for their growth and continuance, such as suitable 

 soil, sufficient food, the requisite percentage of salt, and a temperature 

 favorable to their development. 



Science possesses, as yet, no word by which such a community of living 

 beings may be designated; no word for a community where the sum of spe- 

 cies and individuals, being mutually limited and selected under the average 

 external conditions of life, have, by means of transmission, continued in 

 possession of a certain definite territory. I propose the word biocoenosis for 

 such a community. 



A biocenose may be composed primarily of animals or primarily 

 of plants, but most biocenoses include both plants and animals ( Fig. 

 11.1) and often many species of each kingdom are present. A 

 biocenose need not necessarily be self-sufficient. The oysters of 

 Mobius's original biocenose require food particles carried to them 

 from other areas by water currents. The animals of a cave form a 

 clearly recognized biocenose, but food must be brought in by streams, 

 by the foraging of bats outside, or in some other way. However, 

 most typical biocenoses include species that fulfill the essential func- 

 tions of producer, consumer, reducer, and transformer; these com- 

 munities are thus largely independent of others and, given radiant 

 energy, are relatively self-sufficient. 



The general concept of the community or biocenose as a group 

 of mutually adjusted organisms maintaining themselves in an area 

 is clear, but the recognition of specific communities and their limits 

 is difficult. Part of the difficulty is due to the fact that the community 

 concept has both a functional and a descriptive aspect. Every plant 

 and animal necessarily has fimctional interrelations with a variety 



