xiv CONTENTS 



XXIX. Man's Relatives: The Primates 470 



The origin of primates; primate characteristics; the groups of pri- 

 mates; the ancestry of man. 



XXX. Prehistoric Men 488 



The Pleistocene epoch; fossil men and their relation to modern man. 



XXXI. The Human Species 507 



The unity of mankind; the diversity of mankind; cultural levels and 

 evolutionary trends in man; the zoogeography of man. 



PART IV. THE ECONOMIC AND SOCIAL INTERRELATIONSHIPS OF 

 ORGANISMS 



XXXII. The Physical Environment of Organisms 541 



The energy cycle in the organic world; the physical environments in 

 which organisms live; the physical factors that affect organisms; the 

 soil as an environmental complex. 



XXXIII. The Biotic Environment of Organisms 562 



The biotic environment; biotic potential and environmental resist- 

 ance; biotic factors of the environmental resistance; some cooperative 

 relations among organisms; biotic communities and their successions. 



XXXIV. Summary: Man and the Biological World 587 



Man in his four roles as an organism; the significance of culture, 

 which adds to and partly obscures but does not supplant man's 

 biological heritage. 



Appended:: A Survey of the Kinds of Organisms 593 



A. The Plant Kingdom 595 



B. The Animal Kingdom 627 



List of Visual Aids , 6611 



Index 673 



