THE STUDY OF ZOOLOGY 3 



underlying causes of animal behavior. In its method physiology- 

 is largely experimental. 



4. Ecology, the study of the relations of an animal or plant to 

 its environment both animate and inanimate. It is funda- 

 mentally physiological in character but involves also a considera- 

 tion of morphological features of animals and plants as well as 

 attention to such factors as temperature, moisture, light, pres- 

 sure etc., which make up the nonliving environment. 



5. The study of evolution, the process through which, there is 

 much reason to believe, the great wealth and diversity of life and 

 its distribution in time and space have been brought about. 

 Evolution is a central principle in biology which holds that the 

 present condition of life on the earth has been arrived at through 

 changes extending over long periods of time, and that in general 

 higher forms of life have evolved from lower forms, through 

 natural processes. The fields of study devoted principally to the 

 topic of evolution are: 



a. Paleontology, the study of prehistoric forms of life, a 

 record of whose existence has been preserved in the form of fossils 

 embedded in the earth. It deals with the distribution of organ- 

 isms in time. 



6. Zoogeography, the study of the distribution of animals in 

 space. 



c. Genetics, the study of the origin of the individual 

 organism as distinguished from evolution in which the problem 

 is the origin of kinds of organisms. Genetics is the science of 

 heredity. 



6. Taxonomy or systematic zoology, the science of classification 

 of organisms, which is concerned with naming organisms and 

 indicating as far as possible the relationship between different 

 kinds. 



Structure and Function. — In the various methods of approach- 

 ing the subject of biology, structure of the organism and function 

 form the background of the study. Structure and function 

 represent two aspects of the organization of the living body. A 

 general distinction is sometimes made between structure and 

 function in which structural details are regarded as representing 

 the static side of organization, in the sense that the actual form 

 and structure of the components of the animal body stand for the 

 visible machinery by means of which functions are carried out; 



