THE SCOPE OF ZOOLOGY 15 



Branches of Zoology 



We have now narrowed our consideration down to the subject of 

 zoology, but we still find that this is a rather broad subject and, for 

 purposes of convenience in study, it is broken down into smaller di- 

 visions. We will not attempt to list all of these, but there are some 

 with which the beginning student of zoology should be familiar. 



1. Morphology. This is the phase of zoology which deals with 

 the structure of animals. It is further broken down into : 



a. Anatomy, which is gross structure or that which can be seen 

 with the naked eye. 



b. Histology, which is microscopic structure or that which you 

 can see when you put a small bit of animal tissue under the micro- 

 scope for a detailed study. It is concerned primarily with the over- 

 all appearance of the cells and the materials which lie between the 

 cells. 



c. Cytology, which is the detailed structure of cells. Microscopes 

 must, of course, be used in this study as in histology, but cytology 

 concentrates on the parts that go to make up an individual cell, 

 how they operate in cell division, etc. 



2. Physiology. This is the study of the functioning of the living 

 animal. In other words, how the various parts of the body work to 

 perform the vital life processes, such as circulation, digestion, etc. 



3. Taxonomy. This phase of zoology deals with animal classifica- 

 tion. There are many kinds of animals on the earth and they must be 

 classified in some way. Similarities of morphological and physiological 

 characteristics are usually used as a basis for the classification. 



4. Genetics. This is the study of inheritance or the methods of 

 heredity. It seeks to find the explanation for the similarities and 

 differences that exist between parents and offspring. 



5. Embryology. In this study, the development of the individual 

 animal is traced from its earliest beginning. Since most animals origi- 

 nate from a single cell, that is where embryology starts. It continues 

 through the divisions of this cell to the various parts of the body as 

 they are formed and grow to form the adult type. Much of embryology 

 is concerned with the structure of the embryo at various stages of its 

 development ; hence it might be considered as a branch of morphology, 

 but in recent years there has been an increasing emphasis on the physi- 

 ological features of embryology. In other words, in addition to learn- 

 ing how the embryo develops there is an attempt to learn what physio- 

 logical reactions cause it to develop as it does. 



