RELATIONS AMONG SPECIES 



361 



^climatic 



phic 



Figure 19.6 The kinds of ciimaxes. 



simply termed seres). The other major successions are 

 climatic, physiographic, geologic and biogeographic 

 (Figure 19.7). Climatic succession entails a nongeo- 

 graphic temporal sequence of biotic communities (of- 

 ten climaxes), called cliseres, that reflect climatic 

 change. The climax of climatic succession is a rather 

 nebulous entity, but one might consider it to be the 

 particular climatic climax during a stable period that 

 might terminate a single climatic trend. Physiographic 

 succession consists of eoseres, each a sequence of biotic 

 communities reflecting a constructive or destructive 

 phase of a geomorphic cycle. For practical purposes, 

 there really is no eosere climax. However, if all ele- 

 vating processes were to cease and erosion proceeded 

 to its full extent, a stable state that might be called a 

 climax would exist in the form of 12,000 feet of water 

 covering a uniform ocean bottom. Geologic succession 

 places emphasis on taxa rather than communities. 

 Steps in this succession, geoseres, might be defined as 

 the "ages" or dominance of particular major groups 

 of organisms (e.g., Ages of Monera, Algae, Pterido- 

 phytes, Gymnosperms, Angiosperms, Invertebrates, 

 Fishes, Amphibians, Reptiles, and Mammals). How- 

 ever, there can be confusion of geoseres when plants 

 and animals are considered together because the 

 "ages" of plants and animals overlap but do not 



necessarily coincide exactly with one another. 

 Further confusion is possible because there really is 

 no past geologic climax, nor is there likely to be a 

 future one. For a geologic climax to exist, evolution 

 must cease. Therefore, the only possible culmination 

 with potential stability would be the cessation of life 

 upon our planet. Bwgeographical succession is similar to 

 geologic succession, but places emphasis on the evolu- 



^ rock y 



Figure 19.7 The kinds of succession. Rock succession is not mentioned 

 in the text, but it impiies changes and unique features in rocks and 

 topography that lead to nonclimotic climaxes. 



