1. INTRODUCTION 



Ecology may be defined broadly as the 

 science of the interrelation between living 

 organisms and their environment, including 

 both the physical and the biotic environ- 

 ments, and emphasizing interspecies as well 

 as intraspecies relations. The living or- 

 ganism may be defined, though somewhat 

 incompletely, as a physicochemical mech- 

 anism that is self-regulating and self- 

 perpetuating, and is in process of equifi- 

 bration with its environment. The environ- 

 ment of any organism consists, in final anal- 

 ysis, of everytliing in the universe external 

 to that particular organism. Those parts 

 of the total environment that are evidently 

 of direct importance to the organism 

 are regarded as constituting the effective 

 environment. The relations of any organism 

 or community of organisms with the envi- 

 ronment are, in the language ot Raymond 

 Pearl (p. 266), (1) particular: specific for 

 every organism; (2) continuous: the organ- 

 ism Uving in its environment for its total 

 life; (3) reciprocal: the environment affect- 

 ing the organism, and vice versa; and (4) 

 indissoluble: dissociation of an organism 

 from its environment being impossible. The 

 organism and groups of organisms are the 

 essential biological units in ecology, and we 

 exclude the intraorganismal or cellular en- 

 virormient except as special cases demand 

 its examination. 



The reciprocal relations require especial 

 attention. The interaction of the environ- 

 ment and the organism is obvious in almost 

 every field of biology. Physiological proc- 

 esses are correlated primarily or secondar- 

 ily with environmental fluctuations: energy 

 for life is derived from the environment; 

 growth and development show relationship 

 to environmental factors; environmental 

 forces and substances impinge upon the 

 sense organs of animals and the reactive 

 systems of plants; behavior patterns in large 

 Dart are responses to environmental pat- 



terns; distribution of plants and animals is 

 determined by variations in the environ- 

 mental complex; isolation through environ- 

 mental factors has profoundly influenced 

 genetic systems of organisms, and the en- 

 vironment has acted as a selective agent in 

 deteiTnining the survival of organisms and 

 populations, thus leading to the evolution- 

 ary development of hving systems. 



in its more scientific aspects, ecology is 

 intrinsically a difficult subject. In its rela- 

 tions it depends on many other phases of 

 biology, and it is built directly, as well as 

 indirectly, on the physical sciences. The 

 subsciences of biology and the physical 

 sciences are in turn dependent upon and af- 

 fected by ecology. Yet in its close relation- 

 ship to natural history, ecology is near the 

 stolon from which all biology has develop- 

 ed. As such it sometimes seems deceptively 

 simple, and under many conditions ecology 

 may really be simple. Almost any good, 

 precise observation within its extended bor- 

 ders makes a useful contribution to the 

 mass of needed ecological information. Its 

 wide range of subject matter, open to ex- 

 ploration by diverse techniques, is a major 

 reason for the lack of ready integration of 

 the field of ecology as a whole. It is at 

 any rate obvious that the development of 

 generaUzations and principles in ecology 

 and the orientation of its subject matter 

 with respect to such principles, have been 

 slow. 



Workers in ecology, fike those in any 

 other broad field, face reproach from more 

 narrow specialists. Physiologists, for exam- 

 ple, are hard pressed to meet the rigorous 

 standards of biophysics or biochemistry, 

 to say nothing of those of physics or chem- 

 istry proper. In part this particular diffi- 

 culty is not directly related to subject mat- 

 ter, as evidenced by the relative precision 

 gained by specialists as contrasted with 

 generaUzers in any field. In part the difii- 



