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Linnaean taxonomy

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The title page ofSystema Naturae,Leiden (1735)

Linnaean taxonomycan mean either of two related concepts:

  1. The particular form ofbiological classification(taxonomy) set up byCarl Linnaeus,as set forth in hisSystema Naturae(1735) and subsequent works. In the taxonomy of Linnaeus there are three kingdoms, divided intoclasses,and the classes divided into lower ranks in a hierarchical order.
  2. A term for rank-based classification of organisms, in general. That is, taxonomy in the traditional sense of the word: rank-basedscientific classification.This term is especially used as opposed tocladisticsystematics, which groups organisms intoclades.It is attributed to Linnaeus, although he neither invented the concept of ranked classification (it goes back toPlatoandAristotle) nor gave it its present form. In fact, it does not have an exact present form, as "Linnaean taxonomy" as such does not really exist: it is a collective (abstracting) term for what actually are several separate fields, which use similar approaches.

Linnaean namealso has two meanings, depending on the context: it may either refer to a formal name given by Linnaeus (personally), such asGiraffa camelopardalisLinnaeus, 1758;or a formal name in the accepted nomenclature (as opposed to a modernisticcladename).

The taxonomy of Linnaeus[edit]

In hisImperium Naturae,Linnaeusestablished three kingdoms, namelyRegnum Animale,Regnum VegetabileandRegnum Lapideum.This approach, the Animal, Vegetable and Mineral Kingdoms, survives today in the popular mind, notably in the form of the parlour game question: "Is itanimal, vegetable or mineral?".The work of Linnaeus had a huge impact on science; it was indispensable as a foundation forbiological nomenclature,now regulated by thenomenclature codes.Two of his works, the first edition of theSpecies Plantarum(1753) for plants and the tenth edition of theSystema Naturae(1758), are accepted as part of the starting points of nomenclature; his binomials (names for species) and generic names take priority over those of others.[1]However, the impact he had on science was not because of the value of his taxonomy.

Linnaeus' kingdoms were in turn divided intoclasses,and they, in turn, intoorders,genera(singular:genus), andspecies(singular:species), with an additional rank lower than species, though these do not precisely correspond to the use of these terms in modern taxonomy.[2]

Classification of plants[edit]

InSystema Naturae(1735), his classes and orders of plants, according to hisSystema Sexuale,were not intended to represent natural groups (as opposed to hisordines naturalesin hisPhilosophia Botanica) but only for use in identification. However, in 1737 he publishedGenera Plantarumin which he claimed that his classification of genera was a natural system.[3]His botanical classification and sexual system were used well into the nineteenth century.[4]Within each class were several orders. This system is based on the number and arrangement of male (stamens) and female (pistils) organs.[5]

Key to the Sexual System (from the 10th, 1758, edition of theSystema Naturae)
Kalmiais classified according to Linnaeus' sexual system in class Decandria, order Monogyna, because it has 10stamensand onepistil

The Linnaean classes for plants, in the Sexual System, were (page numbers refer toSpecies plantarum):

  • Classis 1. Monandria: flowers with 1 stamen
  • Classis 2. Diandria: flowers with 2 stamens
  • Classis 3. Triandria: flowers with 3 stamens
  • Classis 4. Tetrandria: flowers with 4 stamens
  • Classis 5. Pentandria: flowers with 5 stamens
  • Classis 6. Hexandria: flowers with 6 stamens
    • Hexandria monogynia pp. 285–352[6]
    • Hexandria polygynia pp. 342–343[7]
  • Classis 7. Heptandria: flowers with 7 stamens
  • Classis 8. Octandria: flowers with 8 stamens
  • Classis 9. Enneandria: flowers with 9 stamens
  • Classis 10. Decandria: flowers with 10 stamens
  • Classis 11. Dodecandria: flowers with 11 to 19 stamens
  • Classis 12. Icosandria: flowers with 20 (or more) stamens,perigynous
  • Classis 13. Polyandria: flowers with many stamens, inserted on thereceptacle
  • Classis 14. Didynamia: flowers with 4 stamens, 2 long and 2 short
    • Gymnospermia[8]
    • Angiospermia[9]
  • Classis 15. Tetradynamia: flowers with 6 stamens, 4 long and 2 short[10]
  • Classis 16. Monadelphia; flowers with the anthers separate, but the filaments united, at least at the base
  • Classis 17. Diadelphia; flowers with the stamens united in two separate groups[14]
  • Classis 18. Polyadelphia; flowers with the stamens united in several separate groups[18]
  • Classis 19. Syngenesia; flowers with stamens united by their anthers[22]
    • Polygamia aequalis[23]
    • Polygamia superba[24]
    • Polygamia frustranea[25]
    • Polygamia necessaria[26]
    • Monogamia[27]
  • Classis 20. Gynandria; flowers with the stamens united to the pistils[28]
  • Classis 21. Monoecia:monoeciousplants
  • Classis 22. Dioecia:dioeciousplants
  • Classis 23. Polygamia:polygamodioeciousplants
  • Classis 24. Cryptogamia: the "flowerless" plants, includingferns,fungi,algae,andbryophytes

The classes based on the number of stamens were then subdivided by the number of pistils, e.g.Hexandria monogyniawith six stamens and one pistil.[29]Index to genera p. 1201[30]

By contrast hisordines naturalesnumbered 69, from Piperitae to Vagae.

Classification for animals[edit]

The 1735 classification of animals

Only in the Animal Kingdom is the higher taxonomy of Linnaeus still more or less recognizable and some of these names are still in use, but usually not quite for the same groups. He divided the Animal Kingdom into six classes. In the tenth edition, of 1758, these were:

Classification for minerals[edit]

His taxonomy ofmineralshas long since been dropped from use. In the tenth edition, 1758, of theSystema Naturae,the Linnaean classes were:

  • Classis 1. Petræ
  • Classis 2. Mineræ
  • Classis 3. Fossilia
  • Classis 4. Vitamentra

Rank-based scientific classification[edit]

Main article:Taxonomy (biology)

This rank-based method of classifying living organisms was originally popularized by (and much later named for) Linnaeus, although it has changed considerably since his time. The greatest innovation of Linnaeus, and still the most important aspect of this system, is the general use ofbinomial nomenclature,the combination of agenusname and a second term, which together uniquely identify eachspeciesof organism within a kingdom. For example, thehumanspecies is uniquely identified within the animal kingdom by the nameHomo sapiens.No other species of animal can have this samebinomen(the technical term for a binomial in the case of animals). Prior to Linnaean taxonomy, animals were classified according to their mode of movement.

Linnaeus's use of binomial nomenclature was anticipated by the theory of definition used inScholasticism.Scholastic logicians and philosophers of nature defined the species human, for example, asAnimal rationalis,whereanimalwas considered a genus andrationalis(Latin for "rational" ) the characteristic distinguishing humans from all other animals. Treatinganimalas the immediate genus of the species human, horse, etc. is of little practical use to the biological taxonomist, however. Accordingly, Linnaeus's classification treatsanimalas a class including many genera (subordinated to the animal "kingdom" via intermediary classes such as "orders" ), and treatshomoas the genus of a speciesHomo sapiens,withsapiens(Latin for "knowing" or "understanding" ) playing a differentiating role analogous to that played, in the Scholastic system, byrationalis(the wordhomo,Latin for "human being", was used by the Scholastics to denote a species, not a genus).

A strength of Linnaean taxonomy is that it can be used to organize the different kinds of livingorganisms,simply and practically. Every species can be given a unique (and, one hopes, stable) name, as compared with common names that are often neither unique nor consistent from place to place and language to language. This uniqueness and stability are, of course, a result of the acceptance by workingsystematists(biologists specializing in taxonomy), not merely of the binomial names themselves, but of the rules governing the use of these names, which are laid down in formalnomenclature codes.

Species can be placed in arankedhierarchy,starting with eitherdomainsorkingdoms.Domains are divided intokingdoms.Kingdoms are divided intophyla(singular:phylum) — foranimals;the termdivision,used forplantsandfungi,is equivalent to the rank of phylum (and the currentInternational Code of Botanical Nomenclatureallows the use of either term). Phyla (or divisions) are divided intoclasses,and they, in turn, intoorders,families,genera(singular:genus), andspecies(singular:species). There are ranks below species: in zoology,subspecies(but seeformormorph); in botany,variety(varietas) andform(forma), etc.

Groups of organisms at any of these ranks are calledtaxa(singular:taxon) ortaxonomic groups.

The Linnaean system has proven robust and it remains the only extant working classification system at present that enjoys universal scientific acceptance. However, although the number of ranks is unlimited, in practice any classification becomes more cumbersome the more ranks are added. Among the later subdivisions that have arisen are such entities as phyla, families, and tribes, as well as any number of ranks with prefixes (superfamilies, subfamilies, etc.). The use of newer taxonomic tools such ascladisticsandphylogenetic nomenclaturehas led to a different way of looking at evolution (expressed in many nestedclades) and this sometimes leads to a desire for more ranks. An example of such complexity is thescheme for mammalsproposed by McKenna and Bell.

Alternatives[edit]

Over time, understanding of the relationships between living things has changed. Linnaeus could only base his scheme on the structural similarities of the different organisms. The greatest change was the widespread acceptance ofevolutionas the mechanism of biological diversity and species formation, following the 1859 publication of Charles Darwin'sOn the Origin of Species.It then became generally understood that classifications ought to reflect thephylogenyof organisms, their descent by evolution. This led toevolutionary taxonomy,where the variousextantandextinctare linked together to construct a phylogeny. This is largely what is meant by the term 'Linnaean taxonomy' when used in a modern context. Incladistics,originating in the work ofWilli Hennig,1950 onwards, each taxon is grouped so as to include the common ancestor of the group's members (and thus to avoidphylogeny). Such taxa may be eithermonophyletic(including all descendants) such as genusHomo,orparaphyletic(excluding some descendants), such as genusAustralopithecus.

Originally, Linnaeus established three kingdoms in his scheme, namely forPlants,Animalsand an additional group forminerals,which has long since been abandoned. Since then, various life forms have been moved into three new kingdoms:Monera,forprokaryotes(i.e., bacteria);Protista,for protozoans and most algae; andFungi.This five kingdom scheme is still far from thephylogeneticideal and has largely been supplanted in modern taxonomic work by a division into three domains:BacteriaandArchaea,which contain the prokaryotes, andEukaryota,comprising the remaining forms. These arrangements should not be seen as definitive. They are based on thegenomesof the organisms; as knowledge on this increases, classifications will change.[31]

Representing presumptive evolutionary relationships within the framework of Linnaean taxonomy is sometimes seen as problematic, especially given the wide acceptance ofcladisticmethodology and numerousmolecular phylogeniesthat have challenged long-accepted classifications. Therefore, some systematists have proposed aPhyloCodeto replace it.

See also[edit]

References[edit]

  1. ^Polaszek 2010,p. 1.
  2. ^Bihrmann 2021.
  3. ^Müller-Wille, Staffan; Reeds, Karen (September 2007)."A translation of Carl Linnaeus's introduction to Genera plantarum (1737)".Studies in History and Philosophy of Science Part C: Studies in History and Philosophy of Biological and Biomedical Sciences.38(3): 563–572.doi:10.1016/j.shpsc.2007.06.003.ISSN1369-8486.PMID17893065.
  4. ^Comstock, J.L. (1837).An introduction to the study of botany: including a treatise on vegetable physiology, and descriptions of the most common plants in the middle and northern states.Robinson, Pratt & Co.
  5. ^Bremer 2007.
  6. ^Linnaeus 1753,Hexandria monogynia i pp. 285–352.
  7. ^Linnaeus 1753,Hexandria polyynia i pp. 342–343.
  8. ^Linnaeus 1753,ii pp. 561–601.
  9. ^Linnaeus 1753,ii pp. 602–639.
  10. ^Linnaeus 1753,ii pp. 640–672.
  11. ^Linnaeus 1753,ii pp. 673–675.
  12. ^Linnaeus 1753,ii pp. 675–683.
  13. ^Linnaeus 1753,ii pp. 683–698.
  14. ^Linnaeus 1753,ii pp. 699–781.
  15. ^Linnaeus 1753,ii pp. 699–701.
  16. ^Linnaeus 1753,ii pp. 701–706.
  17. ^Linnaeus 1753,ii pp. 706–781.
  18. ^Linnaeus 1753,ii pp. 782–788.
  19. ^Linnaeus 1753,ii p. 782.
  20. ^Linnaeus 1753,ii pp. 782–783.
  21. ^Linnaeus 1753,ii pp. 783–788.
  22. ^Linnaeus 1753,ii pp. 789–938.
  23. ^Linnaeus 1753,ii pp. 789–845.
  24. ^Linnaeus 1753,ii pp. 845–904.
  25. ^Linnaeus 1753,ii pp. 904–919.
  26. ^Linnaeus 1753,ii pp. 919–927.
  27. ^Linnaeus 1753,ii pp. 928–938.
  28. ^Linnaeus 1753,ii pp. 939–.
  29. ^"Linnaeus Sexual System".CronkLab.Biodiversity Research Centre, University of British Columbia.Retrieved26 January2015.
  30. ^Linnaeus 1753,Index generum p. 1201.
  31. ^Embley, T. A. & Martin, W. (2006)."Eukaryotic evolution, changes and challenges".Nature.440(7084): 623–630.doi:10.1038/nature04546.PMID16572163.S2CID4396543.

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