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IV. HOW MANY ARE THE KINGDOMS OF ORGANISMS?
Author(s) -
Leedale Gordon F.
Publication year - 1974
Publication title -
taxon
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.819
H-Index - 81
eISSN - 1996-8175
pISSN - 0040-0262
DOI - 10.2307/1218705
Subject(s) - phylum , polyphyly , kingdom , biology , evolutionary biology , monophyly , taxonomy (biology) , phylogenetics , zoology , genealogy , clade , paleontology , genetics , history , gene
Summary The division of living organisms into Plantae and Animalia fails to recognise the major evolutionary discontinuity between prokaryotes and eukaryotes. In addition, fungi and “plant‐animal” unicells lie uncomfortably in such a two‐kingdom system. Systems have been proposed which separate prokaryotes from eukaryotes and divide the latter into several kingdoms. These schemes share two limitations. The “low” eukaryote kingdom (Protoctista or Protista) contains phyla more closely related to phyla of the “higher” kingdoms than to other phyla in the same kingdom. Secondly, the higher kingdoms are polyphyletic to a disturbing degree. Can one make broad classifications without these limitations? A Prokaryota/Eukaryota two‐kingdom scheme is one possibility; another is a four‐kingdom scheme in which the protistan level is absorbed into the eukaryote kingdoms; a third possibility is a system in which phylum and phylogeny units stand as monophyletic kingdoms; such a multikingdom scheme provides fruitful scope for discussion. The Prokaryota/Eukaryota and multikingdom schemes allow flexibility for incorporation of new information on relationships, but may be thought too fragmentary for practical taxonomy. If so, various four‐ or five‐kingdom schemes are available.