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Scientific classification
Domain: Eukaryota
(unranked) Unikonta


Unikonts are members of the Unikonta, a taxonomic group proposed by Thomas Cavalier-Smith. [1][2]

It includes amoebozoa and opisthokonts.[3][4]



The group includes eukaryotic cells that, for the most part, have a single emergent flagellum, or are amoebae with no flagella. The unikonts include opisthokonts (animals, fungi and related forms) and Amoebozoa. By contrast other well-known eukaryotic groups, which more often have two emergent flagella (although there are many exceptions) are often referred to as bikonts. These include Archaeplastida (plants and relatives), Excavata, Rhizaria, and Chromalveolata.


The unikonts have a triple-gene fusion that is lacking in the bikonts. The three genes that are fused together in the unikonts but not bacteria or bikonts encode enzymes for synthesis of the pyrimidine nucleotides: carbamoyl phosphate synthase, dihydroorotase, aspartate carbamoyltransferase. This must have involved a double fusion, a rare pair of events, supporting the shared ancestry of Opisthokonta and Amoebozoa.

Cavalier-Smith [1] originally proposed that unikonts ancestrally had a single flagellum and single basal body. This is unlikely, however, as flagellated opisthokonts, as well as some flagellated Amoebozoa, including Breviata, actually have two basal bodies, as in typical 'bikonts' (even though only one is flagellated in most unikonts). This paired arrangement can also be seen in the organization of centrioles in typical animal cells. In spite of the name of the group, the common ancestor of all 'unikonts' was probably a cell with two basal bodies.


  1. ^ a b Cavalier-Smith T (March 2002). "The phagotrophic origin of eukaryotes and phylogenetic classification of Protozoa". Int. J. Syst. Evol. Microbiol. 52 (Pt 2): 297–354. PMID 11931142.  
  2. ^ Cavalier-Smith, Thomas (2003). "Protist phylogeny and the high-level classification of Protozoa". European Journal of Protistology 39 (4): 338–348. doi:10.1078/0932-4739-00002.  
  3. ^ A Minge M, Silberman JD, Orr RJ, et al. (November 2008). "Evolutionary position of breviate amoebae and the primary eukaryote divergence". Proc. Biol. Sci. 276: 597. doi:10.1098/rspb.2008.1358. PMID 19004754.  
  4. ^ Burki F, Pawlowski J (October 2006). "Monophyly of Rhizaria and multigene phylogeny of unicellular bikonts". Mol. Biol. Evol. 23 (10): 1922–30. doi:10.1093/molbev/msl055. PMID 16829542.  

External links



Up to date as of January 23, 2010

From Wikispecies


Main Page
Cladus: Eukaryota
Supergroup: Unikonta
Cladi: Amoebozoa (phylum) - Opisthokonta
[list of cladi after Cavalier-Smith (2009: 26, 'The primary divergence among unikonts is between Amoebozoa and opisthokonts')]


  • Cavalier-Smith, T. 2009: Megaphylogeny, cell body plans, adaptive zones: causes and timing of eukaryote basal radiations. Journal of eukaryotic microbiology, 56: 26-33. DOI: 10.1111/j.1550-7408.2008.00373.x Abstract


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