Preface 



"Live Alone and Like It" is a slogan that no living thing can adopt. 

 Every plant and animal is subject to both the living and the non-living 

 influences of its surroundings. Every organism depends upon its 

 environment to supply it with vital materials and energy. Every 

 living being must share its world with members of its own species and 

 with members of other species— be they friend or foe. 



Man is no exception. Man is surrounded by many kinds of living 

 things, and he must derive his needs from the world around him. Man 

 must learn to live in adjustment with his fellow men, and with the 

 plants and animals of his environment, and to use his natural resources 

 judiciously, or he will be exterminated. 



Obviously, then, the interrelations of the organism and its environ- 

 ment are crucial; and ecology, which is the study of these interrela- 

 tions, is of great significance. Yet few books are available which deal 

 with the general principles of the whole subject. Most of the books 

 in the field of ecology treat primarily either "plant ecology" or "animal 

 ecology." But animals cannot get along without plants, and plants 

 are almost always vitally influenced by animals. Man is dependent 

 upon both. 



Accounts of the flora and fauna of various regions and descriptions 

 of a variety of habitats have long been available. Early ecologists 

 have investigated the efi^ects of environmental factors on the activities 

 of living things. But not until relatively recently have we realized 

 that plants and animals also react on their surroundings in such a way 

 that they form a reciprocating and integrated system with their 

 environment. The modern ecologist focuses his attention on the 

 dynamic interplay of the forces in the living community. 



The purpose of this book is to bring together in one place and in a 

 simple way the elements of ecology with special emphasis on the 

 modern viewpoint of the science. It is desired to stress the unity of 

 ecology and the necessity for including the influence of both plants 

 and animals as well as the physical forces as part of the environment. 

 The subject is old, but efforts to crystallize the basic principles in any 

 exact way are relatively new. The potential scope of ecology is very 



