CHAPTER XV 



GENERAL DISCUSSION 



I. INTRODUCTION 



We have briefly presented some facts regarding the nature and 

 environmental relations of animals, an account of the environment, and 

 a discussion of the inhabitants of some of the type habitats of the forest 

 and forest border regions. We noted also in preceding chapters some 

 aspect of relations of the animals of the same and of different com- 

 munities to one another, and our relations to them. We may still 

 present (a) the relations of the different communities to one another, 

 (b) the laws governing distribution, and (c) a discussion of the relations 

 of ecology to broader geographic problems. 



II. APPLICATION OF THE LAWS GOVERNING ANIMAL ACTIVITIES TO 

 WORLD AND REGIONAL PROBLEMS 



As was stated in the first chapter, the relative importance of different 

 environmental factors is not definitely known, but probably in local and 

 experimental conditions, land environments can best be measured in 

 terms of evaporating power of the air, light, and materials for abode, 

 aquatic environment by carbon dioxide, oxygen, and materials for abode. 

 In explaining extensive or regional distribution, a few factors have 

 been emphasized and these usually in the sense of barriers. Merriam 

 (48) emphasizes temperature, Walker (128) atmospheric moisture. 

 Heilprin (192, p. 39), like most paleontologists, emphasizes food. 

 Nothing is, I believe, more incorrect than the idea that the same single 

 factor governs the regional distribution of most animal species. Since 

 the environment is a complex of many factors, every animal, while in 

 its normal environmental complex, lives surrounded by and responds 

 to a complex of factors in its normal activities (44, p. 193). Can a 

 single factor control distribution? 



I. REACTIONS TO SINGLE FACTORS 



Considerable physiological study of organisms has been conducted 

 with particular reference to the analysis of the organism itself, but with 

 little reference to natural environments. Many of the factors and con- 

 ditions employed in such experiments are of such a -nature that the 



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