The branch of biology concerned with the classification of organisms. Organisms were formerly grouped into various taxa (singular taxon) on the basis of observable anatomical and morphological structures, but nowadays molecular and genetic information is used increasingly, and classification systems are continually being revised as more information becomes available. Cladistics is an approach to classification based on evolutionary relationships and the assumption that organisms that exhibit homologous structures are derived from a common ancestor and are therefore related by genealogy. An organism is classified according to a hierarchical system as follows:
kingdom, phylum, class, order, family, genus, species.
Intermediate categories such as subphylum or superorder may be used in particularly large groups such as flowering plants, in which the term ‘division’ traditionally replaced phylum. The purpose of taxonomy is basically twofold: to provide a means of ready identification of organisms, and to infer and illustrate evolutionary relationships between them. Classification and the naming of organisms are closely related. All organisms have a binomial Latinized name based on the Linnaean system.See Appendix table 8. |
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