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2 INTRODUCTION: THE FIELD AND PROBLEMS OF BIOLOGY 



Perhaps the best way to get an idea of the scope and content of biology 

 and the light it can throw on many aspects of human function and be- 

 havior is to look at some of the problems we encounter in attempting to 

 comprehend a single living organism. No matter what one we choose — 

 man, or one of the familiar domesticated animals or plants, or any of the 

 innumerable "wild" forms that live all about us — we shall encounter a 

 series of broader and broader -problems as we examine our selected 

 organism from various points of view. 



The organism as an isolated individual. Considered from the sim- 

 plest possible viewpoint, as an isolated individual, without question as 

 to its origin or possible relations to other individuals, our organism still 

 presents two closely related problems: How is it constructed? And how 

 does it work? Neither question has yet been completely answered for 

 even the most familiar organism. The partial answers that have been 

 obtained, however, form a large part of the subject matter of biology. 

 They are fundamental to any understanding and appreciation of the still 

 more complicated problems of organic interrelationships. 



The answer to the query "How is this individual constructed?" will be 

 found to require an analysis of its component parts. Scrutiny of its out- 

 ward form and structure will show it to be made up of diverse parts. 

 These, together with a variety of concealed but equally gross internal 

 structures, will be found to be fabricated from smaller parts; and these 

 in turn from still smaller ones, until the analysis reaches the limits of 

 microscopic detail. Similarly, the attempt to discover "how it works" 

 reveals the same high degree of organization. Such major processes as 

 motion and locomotion, digestion, respiration, coordination, and appro- 

 priate behavior resolve themselves, step by step, into the coordinated 

 functioning of minute individual cells, and finally into the physical and 

 chemical activities of protoplasm. 



The parts that are involved and the way in which they are organized 

 differ widely from one type of organism to another. Nevertheless, in any 

 terrestrial animal large enough to be seen and handled we shall find a high 

 degree of differentiation of parts and much division of labor. We shall 

 find that the individual comprises a number of closely interrelated struc- 

 tural and functional systems, that each system is composed of diverse 

 but coordinated organs, that the organs are built of tissues, and that the 

 tissues are made up of cells and cell products. 



The organism as a link in a sequence of generations. The second 

 viewpoint from which we shall examine the organism relates to its role 

 as a temporary unit in a succession of similar individuals. We find that 

 our individual was produced by parents (rarely by a single parent) very 

 much like itself. We find also that each individual organism has but a 

 limited life span and eventually ceases to exist. In spite of this, however, 



