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, 
(6) the laws governing distribution, and (c) a discussion of the relations 
of ecology to broader geographic problems. 
Il. APPLICATION OF THE LAWS GOVERNING ANIMAL ACTIVITIES TO 
WorRLD 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). Cana 
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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