312 



PRINCIPLES OF ANIMAL BIOLOGY 



Physical Conditions of Ranges. — Lest the ecological factors be I'or- 

 gotten in the study of historical phenomena, it should be observed how 

 different are the conditions obtaining in different ranges. A striking 

 illustration of this is found in the distribution of vegetation. The general 

 vegetation areas of North America are shown in Fig. 267. Coniferous 



J''i(j. 2G7. — Geuerul vegetation areas of North America. {From, liurlingarnc, Heath, Martin 

 and Peirce, "General Bioloyy,'" Henry Holt and Comjmnij, Inc. Prepared by A. G. Vestal.) 



and deciduous foj'csts are sepai-ated l)y pliysical conditions, largely tem- 

 perature, and they in turn determine the location of many animals. The 

 eastern deciduous forests are the home of the opossum, gray fox, fox 

 s(iuirrel, cardinal bii-d, (-arolina ^\'ren, and yellow-breasted chat. The 

 northern coniferous forests shelter the snowshoe rabbit, pine martin, 



