The hierarchy of biological classification's eight major taxonomic ranks. A kingdom contains one or more phyla. Intermediate minor rankings are not shown.
In biology, a phylum (phyla ) is a level of classification or taxonomic rank below Kingdom and above Class. Traditionally, in botany the term division has been used instead of phylum, although the International Code of Nomenclature for algae, fungi, and plants accepts the terms as equivalent.[1] [2] [3] Depending on definitions, the animal kingdom Animalia or Metazoa contains approximately 35 phyla, the plant kingdom Plantae contains about 14, and the fungus kingdom Fungi contains about 8 phyla. Current research in phylogenetics is uncovering the relationships between phyla, which are contained in larger clades, like Ecdysozoa and Embryophyta.[citation needed
Contents 1 General description 1.1 Definition based on genetic relation 1.2 Definition based on body plan 2 Known phyla 2.1 Animals 2.2 Plants 2.3 Fungi 2.4 Protista 2.5 Bacteria 2.6 Archaea 3 See also 4 Notes 5 References 6 External links General description The term phylum was coined in 1866 by Ernst Haeckel from the Greek phylon (φῦλον , "race, stock"), related to phyle (φυλή , "tribe, clan"). In plant taxonomy, August W. Eichler (1883) classified plants into five groups named divisions, a term that remains in use today for groups of plants, algae and fungi.[1] [5] embranchements of Georges Cuvier.[6]
Informally, phyla can be thought of as groupings of organisms based on general specialization of body plan.[7] At its most basic, a phylum can be defined in two ways: as a group of organisms with a certain degree of morphological or developmental similarity (the phenetic definition), or a group of organisms with a certain degree of evolutionary relatedness (the phylogenetic definition).[8] Attempting to define a level of the Linnean hierarchy without referring to (evolutionary) relatedness is unsatisfactory, but a phenetic definition is useful when addressing questions of a morphological nature—such as how successful different body plans were.[citation needed
Definition based on genetic relation The most important objective measure in the above definitions is the "certain degree" that defines how different organisms need to be to be members of different phyla. The minimal requirement is that all organisms in a phylum should be clearly more closely related to one another than to any other group.[8] Even this is problematic because the requirement depends on knowledge of organisms' relationships: as more data become available, particularly from molecular studies, we are better able to determine the relationships between groups. So phyla can be merged or split if it becomes apparent that they are related to one another or not. For example, the bearded worms were described as a new phylum (the Pogonophora) in the middle of the 20th century, but molecular work almost half a century later found them to be a group of annelids, so the phyla were merged (the bearded worms are now an annelid family).[9] On the other hand, the highly parasitic phylum Mesozoa was divided into two phyla (Orthonectida and Rhombozoa) when it was discovered the Orthonectida are probably deuterostomes and the Rhombozoa protostomes.[10]
This changeability of phyla has led some biologists to call for the concept of a phylum to be abandoned in favour of cladistics, a method in which groups are placed on a "family tree" without any formal ranking of group size.[8]
Definition based on body plan A definition of a phylum based on body plan has been proposed by paleontologists Graham Budd and Sören Jensen (as Haeckel had done a century earlier). The definition was posited because extinct organisms are hardest to classify: they can be offshoots that diverged from a phylum's line before the characters that define the modern phylum were all acquired. By Budd and Jensen's definition, a phylum is defined by a set of characters shared by all its living representatives.
This approach brings some small problems—for instance, ancestral characters common to most members of a phylum may have been lost by some members. Also, this definition is based on an arbitrary point of time: the present. However, as it is character based, it is easy to apply to the fossil record. A greater problem is that it relies on a subjective decision about which groups of organisms should be considered as phyla.
The approach is useful because it makes it easy to classify extinct organisms as "stem groups" to the phyla with which they bear the most resemblance, based only on the taxonomically important similarities.[8] However, proving that a fossil belongs to the crown group of a phylum is difficult, as it must display a character unique to a sub-set of the crown group.[8] Furthermore, organisms in the stem group of a phylum can possess the "body plan" of the phylum without all the characteristics necessary to fall within it. This weakens the idea that each of the phyla represents a distinct body plan.[11]
A classification using this definition may be strongly affected by the chance survival of rare groups, which can make a phylum much more diverse than it would be otherwise.[12]
Known phyla Animals Main article: Animal
Total numbers are estimates; figures from different authors vary wildly, not least because some are based on described species,[13] some on extrapolations to numbers of undescribed species. For instance, around 25,000–27,000 species of nematodes have been described, while published estimates of the total number of nematode species include 10,000–20,000; 500,000; 10 million; and 100 million.[14]
Basal/disputed Others
Phylum Meaning Common name Distinguishing characteristic Species described Thorny head Thorny-headed worms[15] :278 Reversible spiny proboscis that bears many rows of hooked spines 7003110000000000000♠ approx. 1,100Little ring :306 Segmented worms Multiple circular segment 17,000 + extant Jointed foot Segmented bodies and jointed limbs, with Chitin exoskeleton 7006125000000000000♠ 1,250,000+ extant;[13] 20,000+ extinctArm foot[15] :336 Lampshells[15] :336 7002300000000000000♠ 300-500 extant; 12,000+ extinctMoss animals Moss animals, sea mats, ectoprocts[15] :332 Lophophore, no pedicle, ciliated tentacles, anus outside ring of cilia 7003600000000000000♠ 6,000 extant[13] Longhair jaw Arrow worms[15] :342 7002100000000000000♠ approx. 100 extantWith a cord Chordates Hollow dorsal nerve cord, notochord, pharyngeal slits, endostyle, post-anal tail 7004550000000000000♠ approx. 55,000+[13] Stinging nettle Cnidarians 7004160000000000000♠ approx. 16,000[13] Comb bearer Comb jellies[15] :256 Eight "comb rows" of fused cilia 7002100000000000000♠ approx. 100-150 extantWheel carrying Symbion Circular mouth surrounded by small cilia, sac-like bodies 7000300000000000000♠ 3+Spiny skin Echinoderms[15] :348 Fivefold radial symmetry in living forms, mesodermal calcified spines 7003750000000000000♠ approx. 7,500 extant;[13] approx. 13,000 extinctInside anus[15] :292 Goblet worms Anus inside ring of cilia 7002150000000000000♠ approx. 150Hairy stomach[15] :288 Gastrotrich worms Two terminal adhesive tubes 7002690000000000000♠ approx. 690Jaw orifice Jaw worms[15] :260 7002100000000000000♠ approx. 100Half cord[15] :344 Acorn worms, hemichordates 7002130000000000000♠ approx. 130 extantMotion snout Mud dragons Eleven segments, each with a dorsal plate 7002150000000000000♠ approx. 150Corset bearer Brush heads Umbrella-like scales at each end 7002122000000000000♠ approx. 122Tiny jaw animals Limnognathia 7000100000000000000♠ 1Soft[15] :320 Mollusks / molluscs Muscular foot and mantle round shell 7004850000000000000♠ 85,000+ extant;[13] 80,000+ extinct[16] Thread like Round worms, thread worms[15] :274 Round cross section, keratin cuticle 7004250000000000000♠ 25,000[13] Thread form[15] :276 Horsehair worms, Gordian worms[15] :276 7002320000000000000♠ approx. 320A sea nymph[15] :270 Ribbon worms, Rhynchocoela[15] :270 7003120000000000000♠ approx. 1,200Claw bearer Velvet worms[15] :328 Legs tipped by chitinous claws 7002200000000000000♠ approx. 200 extantStraight swimming[15] :268 Orthonectids[15] :268 Single layer of ciliated cells surrounding a mass of sex cells 7001260000000000000♠ approx. 26Zeus's mistress Horseshoe worms U-shaped gut 7001110000000000000♠ 11Plate animals Trichoplaxes[15] :242 Differentiated top and bottom surfaces, two ciliated cell layers, amoeboid fiber cells in between 7000100000000000000♠ 1Flat worm[15] :262 Flatworms[15] :262 7004295000000000000♠ approx. 29,500[13] [a] Pore bearer Sponges[15] :246 Perforated interior wall 7004108000000000000♠ 10,800 extant[13] Little Priapus Penis worms 7001200000000000000♠ approx. 20Lozenge animal Rhombozoans[15] :264 Single anteroposterior axial cell surrounded by ciliated cells 7002100000000000000♠ 100+Wheel bearer Rotifers[15] :282 Anterior crown of cilia 7003200000000000000♠ approx. 2,000[13] Small tube Peanut worms Mouth surrounded by invertible tentacles 144-320 Slow step Water bears Four segmented body and head 1,000 Strange form without gut — [17] 7002400000000000000♠ 400+Total: 34 1,525,000 [13]
Plants Main article: Plant
The kingdom Plantae is defined in various ways by different biologists (see Current definitions of Plantae). All definitions include the living embryophytes (land plants), to which may be added the two green algae divisions, Chlorophyta and Charophyta, to form the clade Viridiplantae. The table below follows the influential (though contentious) Cavalier-Smith system in equating "Plantae" with Archaeplastida,[18] a group containing Viridiplantae and the algal Rhodophyta and Glaucophyta divisions.
The definition and classification of plants at the division level also varies from source to source, and has changed progressively in recent years. Thus some sources place horsetails in division Arthrophyta and ferns in division Pteridophyta, while others place them both in Pteridophyta, as shown below. The division Pinophyta may be used for all gymnosperms (i.e. including cycads, ginkgos and gnetophytes),[20] or for conifers alone as below.
Since the first publication of the APG system in 1998, which proposed a classification of angiosperms up to the level of orders, many sources have preferred to treat ranks higher than orders as informal clades. Where formal ranks have been provided, the traditional divisions listed below have been reduced to a very much lower level, e.g. subclasses.[21]
Other algae (Biliphyta)[18]
Division Meaning Common name Distinguishing characteristics Species described [22] Anthoceros -like plantHornworts Horn-shaped sporophytes, no vascular system 7002100000000000000♠ 100-300+Bryum -like plant, moss plantMosses Persistent unbranched sporophytes, no vascular system 7004120000000000000♠ approx. 12,000Chara -like plantCharophytes 7003100000000000000♠ approx. 1,000Yellow-green plant[15] :200 Chlorophytes 7003700000000000000♠ approx. 7,000Cycas -like plant, palm-like plantCycads Seeds, crown of compound leaves 7002100000000000000♠ approx. 100-200Ginkgo -like plantGinkgo, maidenhair tree Seeds not protected by fruit (single living species) 7000100000000000000♠ only 1 extant; 50+ extinctBlue-green plant Glaucophytes 7001130000000000000♠ 13Gnetum -like plantGnetophytes Seeds and woody vascular system with vessels 7001700000000000000♠ approx. 70[20] Lycophyta
Lycopodium -like plantWolf plant
Clubmosses & spikemosses 7003129000000000000♠ 1,290 extantMagnolia -like plantFlowering plants, angiosperms Flowers and fruit, vascular system with vessels 7005300000000000000♠ 300,000[28] Hepatophyta
Marchantia -like plantLiver plant
Liverworts Ephemeral unbranched sporophytes, no vascular system 7003900000000000000♠ approx. 9,000[20] Coniferophyta
Pinus -like plantCone-bearing plant
Conifers Cones containing seeds and wood composed of tracheids 7002629000000000000♠ 629 extant[citation needed Pteris -like plant, fern plantFerns & horsetails 7003900000000000000♠ approx. 9,000 (not including lycophytes)Rose plant Red algae 7003700000000000000♠ approx. 7,000Total: 14
Fungi Main article: Fungi
Division Meaning Common name Distinguishing characteristics Bladder fungus[15] :396 Ascomycetes,[15] :396 sac fungi Small base fungus[15] :402 Basidiomycetes[15] :402 Offshoot branch fungus[30] Blastoclads Little cooking pot fungus[31] Chytrids Ball of yarn fungus[15] :394 Glomeromycetes, AM fungi[15] :394 Small seeds[32] Microsporans[15] :390 New beautiful whip fungus[33] Neocallimastigomycetes Pair fungus[15] :392 Zygomycetes[15] :392 Total: 8
Phylum Microsporidia is generally included in kingdom Fungi, though its exact relations remain uncertain,[34] and it is considered a protozoan by the International Society of Protistologists[35] (see Protista, below). Molecular analysis of Zygomycota has found it to be polyphyletic (its members do not share an immediate ancestor),[36] which is considered undesirable by many biologists. Accordingly, there is a proposal to abolish the Zygomycota phylum. Its members would be divided between phylum Glomeromycota and four new subphyla incertae sedis (of uncertain placement): Entomophthoromycotina, Kickxellomycotina, Mucoromycotina, and Zoopagomycotina.[34]
Protista Main article: Protista taxonomy
Kingdom Protista (or Protoctista) is included in the traditional five- or six-kingdom model, where it can be defined as containing all eukaryotes that are not plants, animals, or fungi.[15] :120 Protista is a polyphyletic taxon[37] (it includes groups not directly related to one another), which is less acceptable to present-day biologists than in the past. Proposals have been made to divide it among several new kingdoms, such as Protozoa and Chromista in the Cavalier-Smith system.[38]
Protist taxonomy has long been unstable,[39] with different approaches and definitions resulting in many competing classification schemes. The phyla listed here are used for Chromista and Protozoa by the Catalogue of Life,[40] adapted from the system used by the International Society of Protistologists.[35]
Phylum/Division Meaning Common name Distinguishing characteristics Example Amorphous animal Amoebas Amoeba Two ring Funnel animal Cilia bearer Ciliates Paramecium True eye animal Euglena Hole bearers Forams Complex shells with one or more chambers Forams Groove animal Giardia Small spore Suckling animal Slime molds Yellow plant Diatoms Diatoms Egg fungus[15] :184 Oomycetes Ray animal Radiolarians Total: 20
The Catalogue of Life includes Rhodophyta and Glaucophyta in kingdom Plantae,[40] but other systems consider these phyla part of Protista.[41]
Bacteria Main article: Bacterial phyla
Currently there are 29 phyla accepted by List of Prokaryotic names with Standing in Nomenclature (LPSN)[42]
Armatimonadetes Bacteroidetes Caldisericum exile is the sole representativeChrysiogenes arsenatis , Desulfurispira natronophila , Desulfurispirillum alkaliphilum )Deferribacteres Deinococcus radiodurans and Thermus aquaticus are "commonly known" species of this phylaDictyoglomi Fibrobacteres Fusobacteria Gemmatimonadetes Nitrospira Planctomycetes Escherichia coli or Pseudomonas aeruginosa Borrelia burgdorferi , which causes Lyme diseaseSynergistetes Mycoplasma )Thermodesulfobacteria Verrucomicrobia Archaea Main article: Archaea
Currently there are 5 phyla accepted by List of Prokaryotic names with Standing in Nomenclature (LPSN).[42]
Korarchaeota Thaumarchaeota See also Biology portal Cladistics Phylogenetics Systematics Taxonomy Notes References ^ a b McNeill, J.; et al., eds. (2012). International Code of Nomenclature for algae, fungi, and plants (Melbourne Code), Adopted by the Eighteenth International Botanical Congress Melbourne, Australia, July 2011 (electronic ed.). International Association for Plant Taxonomy. Retrieved 2017-05-14 . .mw-parser-output cite.citationfont-style:inherit.mw-parser-output .citation qquotes:"""""""'""'".mw-parser-output .citation .cs1-lock-free abackground:url("//upload.wikimedia.org/wikipedia/commons/thumb/6/65/Lock-green.svg/9px-Lock-green.svg.png")no-repeat;background-position:right .1em center.mw-parser-output .citation .cs1-lock-limited a,.mw-parser-output .citation .cs1-lock-registration abackground:url("//upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Lock-gray-alt-2.svg/9px-Lock-gray-alt-2.svg.png")no-repeat;background-position:right .1em center.mw-parser-output .citation .cs1-lock-subscription abackground:url("//upload.wikimedia.org/wikipedia/commons/thumb/a/aa/Lock-red-alt-2.svg/9px-Lock-red-alt-2.svg.png")no-repeat;background-position:right .1em center.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registrationcolor:#555.mw-parser-output .cs1-subscription span,.mw-parser-output .cs1-registration spanborder-bottom:1px dotted;cursor:help.mw-parser-output .cs1-ws-icon abackground:url("//upload.wikimedia.org/wikipedia/commons/thumb/4/4c/Wikisource-logo.svg/12px-Wikisource-logo.svg.png")no-repeat;background-position:right .1em center.mw-parser-output code.cs1-codecolor:inherit;background:inherit;border:inherit;padding:inherit.mw-parser-output .cs1-hidden-errordisplay:none;font-size:100%.mw-parser-output .cs1-visible-errorfont-size:100%.mw-parser-output .cs1-maintdisplay:none;color:#33aa33;margin-left:0.3em.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration,.mw-parser-output .cs1-formatfont-size:95%.mw-parser-output .cs1-kern-left,.mw-parser-output .cs1-kern-wl-leftpadding-left:0.2em.mw-parser-output .cs1-kern-right,.mw-parser-output .cs1-kern-wl-rightpadding-right:0.2em^ "Life sciences". 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Usually organisms were grouped according to their morphological similarities as perceived by those early workers, and those groups were then grouped according to their similarities, and so on, to form a hierarchy. ^ a b c d e Budd, G.E.; Jensen, S. (May 2000). "A critical reappraisal of the fossil record of the bilaterian phyla". Biological Reviews . 75 (2): 253–295. doi:10.1111/j.1469-185X.1999.tb00046.x. PMID 10881389. Retrieved 2007-05-26 . ^ Rouse G.W. (2001). "A cladistic analysis of Siboglinidae Caullery, 1914 (Polychaeta, Annelida): formerly the phyla Pogonophora and Vestimentifera". Zoological Journal of the Linnean Society . 132 (1): 55–80. doi:10.1006/zjls.2000.0263. ^ Pawlowski J, Montoya-Burgos JI, Fahrni JF, Wüest J, Zaninetti L (October 1996). "Origin of the Mesozoa inferred from 18S rRNA gene sequences". Mol. Biol. Evol . 13 (8): 1128–32. doi:10.1093/oxfordjournals.molbev.a025675. PMID 8865666. ^ Budd, G. E. (September 1998). "Arthropod body-plan evolution in the Cambrian with an example from anomalocaridid muscle". Lethaia . 31 (3): 197–210. doi:10.1111/j.1502-3931.1998.tb00508.x. ^ Briggs, D. E. G.; Fortey, R. A. (2005). "Wonderful strife: systematics, stem groups, and the phylogenetic signal of the Cambrian radiation". Paleobiology . 31 (2 (Suppl)): 94–112. doi:10.1666/0094-8373(2005)031[0094:WSSSGA]2.0.CO;2. ^ a b c d e f g h i j k l Zhang, Zhi-Qiang (2013-08-30). "Animal biodiversity: An update of classification and diversity in 2013. In: Zhang, Z.-Q. (Ed.) Animal Biodiversity: An Outline of Higher-level Classification and Survey of Taxonomic Richness (Addenda 2013)". Zootaxa . 3703 (1): 5. doi:10.11646/zootaxa.3703.1.3. ^ Felder, Darryl L.; Camp, David K. (2009). Gulf of Mexico Origin, Waters, and Biota: Biodiversity . Texas A&M University Press. p. 1111. 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(October 2009), "A phylogenetic classification of the land plants to accompany APG III", Botanical Journal of the Linnean Society , 161 (2): 122–127, doi:10.1111/j.1095-8339.2009.01002.x ^ Mauseth, James D. (2012). Botany : An Introduction to Plant Biology (5th ed.). Sudbury, MA: Jones and Bartlett Learning. ISBN 978-1-4496-6580-7. p. 489^ Crandall-Stotler, Barbara; Stotler, Raymond E. (2000). "Morphology and classification of the Marchantiophyta". In A. Jonathan Shaw & Bernard Goffinet (Eds.). Bryophyte Biology . Cambridge: Cambridge University Press. p. 21. ISBN 978-0-521-66097-6. CS1 maint: Uses editors parameter (link) ^ Holt, Jack R.; Iudica, Carlos A. (1 October 2016). "Blastocladiomycota". Diversity of Life . Susquehanna University. Retrieved 29 December 2016 . ^ Holt, Jack R.; Iudica, Carlos A. (9 January 2014). "Chytridiomycota". Diversity of Life . Susquehanna University. Retrieved 29 December 2016 . ^ Holt, Jack R.; Iudica, Carlos A. (12 March 2013). "Microsporidia". Diversity of Life . Susquehanna University. Retrieved 29 December 2016 . ^ Holt, Jack R.; Iudica, Carlos A. (23 April 2013). "Neocallimastigomycota". Diversity of Life . Susquehanna University. Retrieved 29 December 2016 . ^ a b Hibbett DS, Binder M, Bischoff JF, Blackwell M, Cannon PF, Eriksson OE, et al. (May 2007). "A higher-level phylogenetic classification of the Fungi" (PDF) . Mycological Research . 111 (Pt 5): 509–47. CiteSeerX 10.1.1.626.9582 . doi:10.1016/j.mycres.2007.03.004. PMID 17572334. Archived from the original (PDF) on 26 March 2009. ^ a b Ruggiero, Michael A.; Gordon, Dennis P.; Orrell, Thomas M.; et al. (29 April 2015). "A Higher Level Classification of All Living Organisms". PLOS One . 10 (6): e0119248. doi:10.1371/journal.pone.0119248. PMC 4418965 . PMID 25923521. ^ White, Merlin M.; James, Timothy Y.; O'Donnell, Kerry; et al. (Nov–Dec 2006). "Phylogeny of the Zygomycota Based on Nuclear Ribosomal Sequence Data". Mycologia . 98 (6): 872–884. doi:10.1080/15572536.2006.11832617. ^ Hagen, Joel B. (January 2012). "Five Kingdoms, More or Less: Robert Whittaker and the Broad Classification of Organisms". BioScience . 62 (1): 67–74. doi:10.1525/bio.2012.62.1.11. ^ Blackwell, Will H.; Powell, Martha J. (June 1999). "Reconciling Kingdoms with Codes of Nomenclature: Is It Necessary?". Systematic Biology . 48 (2): 406–412. doi:10.1080/106351599260382. ^ Davis, R. A. (19 March 2012). "Kingdom PROTISTA". College of Mount St. Joseph . Retrieved 28 December 2016 . ^ a b "Taxonomic tree". Catalogue of Life . 23 December 2016. Retrieved 28 December 2016 . ^ Corliss, John O. (1984). "The Kingdom Protista and its 45 Phyla". BioSystems . 17 (2): 87–176. doi:10.1016/0303-2647(84)90003-0. ^ a b J.P. Euzéby. "List of Prokaryotic names with Standing in Nomenclature: Phyla". Retrieved 2016-12-28 . External links Look up Phylum
Are phyla "real"? Is there really a well-defined "number of animal phyla" extant and in the fossil record? Major Phyla Of Animals Taxonomic ranks
Domain /SuperkingdomKingdom Subkingdom Infrakingdom/Branch Superphylum/Superdivision Phylum/Division Subphylum Infraphylum Microphylum Superclass Class Subclass Infraclass Parvclass Magnorder Superorder Order Suborder Infraorder Parvorder Section (zoo. ) Superfamily Family Subfamily Infrafamily Supertribe Tribe Subtribe Infratribe Genus Subgenus Section (bot. ) Series (bot. ) Species Subspecies Variety Form
