GENERAL ZOOLOGY 



Botany is the science of plant life. Zoology is the science of animal life. 

 We observe different aspects of animal life, and each branch of zoology has 

 its name. When we study the structure of animals or find the parts of which 

 they are composed, we call our knowledge morphology. Physiology is the 

 study of function, or the ways in which the parts of animals work. Embryology 

 is the study of the development of the individual, the changes through which 

 a fertilized egg passes from its embryonic stages to the adult form. Genetics 

 is the study of heredity and variation. Taxonomy is the study of the classi- 

 fication of animals into groups on the basis of structural similarity. Ecology 

 is the study of animals in relation to both the living and the non-living 

 constituents of their environments, or surroundings. Zoogeography is the 

 study of animal distribution on the earth's surface at any particular period. 

 Paleontology is the study of animal distribution on the earth's surface from 

 the distant past to the present in successive geologic periods; this includes 

 the study of the structure of fossil remains of extinct animals and comparison 

 among those found at dififerent periods. 



Two major generalizations have been formulated and verified on the basis 

 of observations and experiments in these several subdivisions of biological 

 science. These are the Cell Theory and the Theory of Organic Evolution. The 

 first of these is both a light illuminating major areas of biological information 

 and a tool for extending the boundaries of these areas. In the following 

 chapter we shall begin to show you how important the Cell Theory is in 

 understanding any single living individual. On the other hand, the second of 

 the great generalizations of biological science, the Theory of Organic Evo- 

 lution, brings together in a pattern of unity and continuity the varying 

 expressions of life in the countless thousands of kinds of individuals. When 

 you have had the opportunity to learn about some of these many groups of 

 animals, the Theory of Organic Evolution will be discussed in the final 

 chapter of this book. 



Earlier in this chapter science was listed as a cultural subject. It is as 

 such that we wish to present the science of zoology. The theories of biology 

 have made a deep impression on man's thinking, his literature, and his social 

 philosophy. No better illustration can be cited than the Theory of Organic 

 Evolution. Laws have been passed to suppress it, churchmen have debated 

 its merits, and wars have been justified by its use. In most cases exact 

 information about the material correlated by this theory has not been used by 

 those who would discredit it. They have not understood that the test of a 

 theory is a very simple one. It must explain facts which can be observed. 

 If any theory does that, no legislation, no debate, and no misuse can con- 

 tribute to its downfall. With the information to be gained from this book you 

 will be in a better position to accept or reject on their merits many ideas 

 about biology with which you will come in contact outside the classroom. 

 You will be more competent to judge the soundness of social legislation 

 supposedly grounded in biological principles. And, if you are going to be a 

 farmer or a physician, what you learn here will be found basic to the applied 



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