SECTION III. POPULATIONS 



18. GENERAL PROPERTIES OF POPULATIONS 



Up to this point the discussion has focussed 

 largely on what has been called contem- 

 porary operational aspects. Under this 

 heading certain principles that concern the 

 physical and biotic environment of organ- 

 isms have been set forth. These have been 

 largely, although not exclusively, concerned 

 with individual organisms. Our emphasis 

 now shifts. Using the ideas developed ear- 

 lier as background material, we turn our 

 attention first to the population, and then to 

 the community; and, finally, to the eco- 

 logical aspects of evolution. The present 

 section deals with the population per se. 

 Here it will be our responsibility to show 

 first, that the population, both infrasocial 

 and social, can be studied and interpreted 

 with some rigor; second, that certain eco- 

 logical principles emerge from such anal- 

 yses; and tliird, that these principles are 

 fundamental to the understanding of a more 

 complex ecological group, the community. 

 The material of this section also bears upon 

 the section on Evolution (V), as we shall 

 see. 



In developing these points the discussion 

 is organized in the following manner: 

 General Properties of Populations (Chap. 

 18); Biological Backgrounds for Population 

 Studies (Chap. 19); Certain Demographic 

 Backgrounds for Population Studies (Chap. 

 20); The Growth-Form of Populations 

 (Chap. 21); Population Factors and Se- 

 lected Population Problems (Chap. 22); 

 Animal Aggregations (Chap. 23); and The 

 Organization of Insect Societies (Chap. 

 24). 



This treatment has a certain underlying 

 logic. Chapter 18 (the present chapter) is 

 preliminary in the sense that it deals with 

 the broad questions of definition and orien- 

 tation. Chapters 19 and 20 partially lay the 

 foundation essential to any understanding 

 of population operations, namely: reproduc- 



263 



tion, mortaUty, and dispersion as they re- 

 late to group survival. The chapter on 

 Growth-Form (21) is predicated on the 

 idea that change (or stabiUty) of popula- 

 tion numbers furnishes the best end crite- 

 rion of events within that population. Chap- 

 ter 22 attempts to order and make meaning- 

 ful certain of the actual factors that pro- 

 duce the observed growth-form; to discuss 

 the interoperation of these factors, or, bet- 

 ter put, their integration; and to review 

 selected problems in the field of population 

 ecology. Chapters 23 and 24 discuss popu- 

 lations that have distinct subsocial and so- 

 cial aspects and lead to a treatment of the 

 highly organized societies of social insects. 

 In this discussion no serious fine of dis- 

 tinction will be drawn between experimen- 

 tal (laboratory) and natural populations, or 

 between an aquatic and a terrestrial popu- 

 lation. While it will be necessary now and 

 then to point out dissimilarities between 

 these groups, the primary interest centers 

 on their common properties. In other words, 

 this is not a discussion of certain types of 

 populations, but, rather, of general facts 

 and principles common to many popula- 

 tions. This approach is based on the belief 

 that any established population when effec- 

 tively studied will contribute to a general 

 ecology of populations irrespective of the 

 type of group considered. 



POPULATION PROPERTIES 



A population has characteristics that it 

 shares with an organism as well as charac- 

 teristics that are its own unique possession. 

 The former might be called in a loose sense 

 its "biological attributes;" the latter its 

 "unique attributes," which are largely statis- 

 tical. This is not to say that a population is 

 unique only as a statistical entity. It is to 

 say that the biological features express 

 themselves as statistical functions which 



