Phylogenetic Classification (AQA A Level Biology) : Revision Note

Phylogenetic classification

• The phylogenetic system of taxonomy arranges organisms into groups based on their evolutionary origins and relationships

• Under the phylogenetic classification system:

  • there is a hierarchy of groups, in which smaller groups are placed within larger groups

  • there is no overlap between groups

  • each group is called a taxon (plural taxa)

• Grouping organisms in this way is helpful for several reasons

  • Scientists can communicate clearly about different species

  • Knowledge that relates to one species can often be partially applied to other, closely related species, e.g. if one species in a taxon has medicinal properties then it is likely that other species will too

  • It allows scientists to gain an accurate count of the number of species, which is useful for conservation purposes

• Taxonomic groups include (in descending order of size):

  • domain

  • kingdom

  • phylum

  • class

  • order

  • family

  • genus

  • species

• Biological classification changes as more molecular analysis is completed; this means that phylogenetic classification is becoming more accurate over time

  • E.g. the five kingdoms classification system (animals, plants, fungi, protists, bacteria) has now been incorporated into the three domains system (below)