INTRODUCTION: THE FIELD AND PROBLEMS OF BIOLOGY 3 



the race to which it belongs continues. The organism is thus more than 

 an individual ; it also functions as a member of its race — a link in a con- 

 tinuing sequence of individuals. 



Here we encounter a new group of problems. How is a new individual 

 produced? To what extent and by what means are the characteristics of 

 the parent reproduced in the offspring and in the offspring's progeny? 

 Does the role of the organism as an individual conflict or fit in with its 

 role as a member of the race, or are these two aspects of the organism 

 wholly unrelated ? The answers to these questions are not only fundamen- 

 tal to a comprehension of the living world in general but also the basis 

 for an understanding of many important human problems — sex and 

 reproduction, the role of biological inheritance in relation to stability 

 and change in populations and societies, and the individual man or 

 woman's potential value as a contributor to the next generation. 



The organism as the product of evolution. From a third and still 

 broader viewpoint we shall compare an organism with other forms of life 

 about it. We find that its individual pattern of structure and function 

 and the details of its reproductive processes differ more or less from those 

 of other organisms. We find not only that the individual is a member of a 

 sequence of generations but that it also belongs to a much larger assem- 

 blage of closely similar individuals that we recognize as a kind or species. 

 Most species comprise many thousands or millions of similar individuals. 

 We find that this species is, in turn, a member of a still larger assemblage 

 of several or many similar species, termed a genus; that genera (plural 

 of genus) can be grouped into families, families* into orders, orders into 

 classes, etc. — progressively larger and larger groups that include forms 

 having less and less closely similar structures. 



All told, more than a million different kinds of organisms are known to 

 exist. They are grouped into two great kingdoms, animal and plant, and 

 these are subdivisible into phyla, classes, orders, families, genera, and 

 species. When we seek to account for this tremendous variety in the 

 forms of life and for their graduated degrees of likeness and difference, we 

 are led to the conclusion that organisms are all related by blood ties. 

 Their similarities are caused by descent from common ancestors; their 

 differences are due to the remoteness of such common ancestors in the 

 immensity of past time. This is the broad concept; deciphering the details 

 of relationship is still in its initial stages, so that the study of organisms 

 from this viewpoint is still largely a program for the future. But the more 

 data we gather, the more certain seems the conclusion. We see the or- 

 ganism before us as the end product of a long history of survival and 

 change. We see that much of its structure and functioning and its repro- 

 ductive processes bear the impress of former adaptations for existence. 

 This concept applies to man and to all other organisms and provides the 



