Strengths and weakness summarized. 510 index page Introduction to Chapter 14. Conflict arises between the need for an immediately practical method for classifying organisms and the need for evolutionary principles to justify the resulting classification. The two basic principles for classifying organisms are phenetic similarity , and phylogenetic relationships. Evolutionary classification is a somewhat muddled combination, traditionally useful but not rigorous by any strict criterion.
Biologists classify species into a hierarchy of groups.
The hierarchy of biological groups was obvious long before Darwin, and formed the basis for Linnaean classification. Darwin offered an explanation for why this pattern exists. How particular groupings should be recognized and named is the problem of classification. There are phenetic and phylogenetic principles of classification. Sometimes both phenetic similarity and phylogenetic relationships provide suggest coinciding groups.