CHAPTER XIII 



SOME OTHER TYPES OF INDIVIDUAL 

 ORGANIZATION: VARIETY OF STRUCTURE 

 VERSUS UNIFORMITY OF FUNCTION 



One needs only to look about him to see something of the extraordinary 

 variety of size, form, and structure that exists among organisms. When 

 the world revealed by the microscope is also considered, the diversity 

 of living things proves to be very great indeed. Considerably more than 

 a million kinds of animals and plants are known today, and additional 

 ones are constantly being discovered. Out of this vast assemblage, we 

 have examined two types in some detail — man, to illustrate the problems 

 of individual structure and functioning among animals, and a flowering 

 plant, to show how these problems are met by a member of the plant 

 kingdom. Our survey of these has now been almost completed; but a 

 question that still confronts us is to what extent these selected examples 

 are representative of other organisms. In briefly considering this ques- 

 tion, we shall also, in a sense, be summarizing the essential features of 

 individual organization and functioning, freed from much specific detail 

 that has necessarily been included in our treatment of man and the higher 

 plants. 



The thesis of this chapter is that, no matter what their size, form, or 

 structure, all individual organisms encounter the same basic problems of 

 living but solve these problems in unlike ways. The number of different 

 ways of doing the necessary tasks and of types of organization associated 

 with these methods is not, however, so great as might be supposed. We 

 have already seen that the most basic divergence among organisms lies in 

 the means by which the problem of nutrition has been met. The plant 

 has adopted one method, the animal another, and the consequences are 

 so far-reaching that we shall have to examine the chief patterns of animal 

 and of plant life separately and by somewhat different treatments. 



THE VARIED PATTERNS OF ANIMAL LIFE 



If we ignore all except the most striking and fundamental differences 

 among animals, we can group the more than three-quarter million known 

 kinds into a few major assemblages, based on different degrees of com- 



177 



