The process of evolution is sometimes divided into microevolution 

 (changes within populations) and macroevoltition (the origin of 

 major variation patterns). Where to draw the distinction 

 is an arbitrary decision, which we prefer not to make. In the 

 preceding section we have considered prijnarih/ changes witJiin 

 populations. In this section the ivays in which evolving populations 

 change and interact to produce the diverse life forms on the earth 

 are presented. 



Chapter 10 deals with the basic splitting process of evolution: the 

 ways in which a single evolving entity becomes two or more 

 entities. This subject is discussed first by comparing different 

 patterns of diversification which have been observed and then 

 attempting to explain how thcij jnight hove come about. 



Chapter 11 is concerned with the patterns produced over long 

 periods of time by populations evolving and dividing and also 

 becoming extinct. No special factors are postulated to account for 

 the evidence derived from a study of the fossil record, which is 

 accepted as fragmentary and biased in various ways. The same 

 processes that produce elaboration of different populations across a 

 diversified habitat arc viewed as being responsible for the elabora- 

 tion of populations through time. The apparent problem of how 

 "higher" taxonomic categories arise is considered an artifact 

 created by the taxonomic method applied to situations where much 

 extinction and loss of data have occurred. 



