For other uses, see Phyla
In biology, a phylum (English pronunciation: /ˈfaɪləm/; plural: phyla)[note 1] is a taxonomic rank below kingdom and above class. Traditionally, in botany the term "division" is used instead of "phylum", although in 1993 the International Botanical Congress accepted the designation "phylum". The kingdom Animalia contains approximately 35 phyla; the kingdom Plantae contains 12 phyla. Current research in phylogenetics is uncovering the relationships between phyla, which are contained in larger clades, like Ecdysozoa and Embryophyta.
General description and familiar examples 
Concepts of animal phyla have changed importantly from their origins in the six Linnaean classess and the four "embranchements" of Georges Cuvier. Haeckel introduced the term phylum, based on the Greek word phylon. In plant taxonomy, Eichler (1883) classified all plants into five groups, named divisions.  Informally, phyla can be thought of as grouping organisms based on general specialization of body plan. At the most basic level, 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). Attempting to define a level of the Linnean hierarchy without referring to (evolutionary) relatedness is an unsatisfactory approach, but the phenetic definition is more useful when addressing questions of a morphological nature—such as how successful different body plans were.
Definition based on genetic relation 
The largest objective measure in the above definitions is the "certain degree"—how unrelated do organisms need to be to be members of different phyla? The minimal requirement is that all organisms in a phylum should be related closely enough for them to be clearly more closely related to one another than to any other group. However, even this is problematic, as the requirement depends on our current knowledge about organisms' relationships: As more data becomes available, particularly from molecular studies, we are better able to judge 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) when described in 1914, but molecular work almost a century later found them closely related to annelids and merged the phyla, so that the bearded worms are now an annelid family. Likewise, the highly parasitic phylum Mesozoa was divided into two phyla Orthonectida and Rhombozoa, when it was discovered the Orthonectida are deuterostomes and the Rhombozoa protostomes.
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. So as to provide a handle on the size and significance of groups, a "body-plan" based definition of a phylum has been proposed by paleontologists Graham Budd and Sören Jensen. The definition was posited by paleontologists because extinct organisms are typically hardest to classify; they can be off-shoots that diverged from a phylum's line before the characters that define the modern phylum were all acquired.
Definition based on body plan 
By Budd and Jensen's definition, phyla are defined by a set of characters shared by all their living representatives. This has a couple of small problems—for instance, characters common to most members of a phylum may be secondarily lost by some members. It is also defined 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 more major problem is that it relies on an objective decision of which group of organisms should be considered a phylum.
Its utility is that 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. 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. 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.
Based upon this definition, which some say is unreasonably affected by the chance survival of rare groups, which vastly increase the size of phyla, representatives of many modern phyla did not appear until long after the Cambrian.
Animal phyla 
||This section needs additional citations for verification. (February 2013)
||Thorny headed worms
||Reversible spiny proboscis
||No mouth or alimentary canal (alimentary canal = digestive tract in digestive system)
||Multiple circular segment
||Lophophore and pedicle
||Moss animals, sea mats
||Lophophore, no pedicle, ciliated tentacles
||Chitinous spines either side of head, fins
approx. 100 extant|
||With a cord
||Hollow dorsal nerve cord, notochord, pharyngeal slits, endostyle, post-anal tail
||Nematocysts (stinging cells)
||Eight "comb rows" of fused cilia
approx. 100 extant|
||Circular mouth surrounded by small cilia
||Fivefold radial symmetry in living forms, mesodermal calcified spines
approx. 7,000 extant; approx. 13,000 extinct|
||Anus inside ring of cilia
||Two terminal adhesive tubes
||Acorn worms, pterobranchs
||Stomochord in collar, pharyngeal slits
approx. 100 extant|
||Eleven segments, each with a dorsal plate
||Umbrella-like scales at each end
||Tiny jaw animals
||Accordion-like extensible thorax
||Mollusks / molluscs
||Muscular foot and mantle round shell
||Round cross section, keratin cuticle
||A sea nymph
||Legs tipped by chitinous claws
approx. 200 extant|
||Single layer of ciliated cells surrounding a mass of sex cells
||Perforated interior wall
||Single anteroposterior axial cell surrounded by ciliated cells
||Anterior crown of cilia
||Mouth surrounded by invertible tentacles
||Four segmented body and head
||Others (Radiata or Parazoa)
Groups formerly ranked as phyla 
Plant divisions 
||This section needs additional citations for verification. (July 2011)
||Horn-shaped sporophytes, no vascular system
||Persistent unbranched sporophytes, no vascular system
||Ephemeral unbranched sporophytes, no vascular system
||Wolf foot plants
||Clubmosses & Spikemosses
||Microphyll leaves, vascular system
||Ferns & Horsetails
||Prothallus gametophytes, vascular system
||Fern with seeds plant
||Only known from fossils, mostly Devonian, ranking in dispute
||Cones containing seeds and wood composed of tracheids
||Seeds, crown of compound leaves
||Seeds not protected by fruit (single living species)
||Seeds and woody vascular system with vessels
|Anthophyta (or Magnoliophyta)
||Flowers and fruit, vascular system with vessels
Fungal divisions 
Bacterial Phyla/Divisions 
Currently there are 29 phyla accepted by LPSN
- Acidobacteria, phenotipically diverse and mostly uncultured
- Actinobacteria, High-G+C Gram positive species
- Aquificae, only 14 thermophilic genera, deep branching
- Caldiserica, formerly candidate division OP5, Caldisericum exile is the sole representative
- Chlamydiae, only 6 genera
- Chlorobi, only 7 genera
- Chrysiogenetes, only 3 genera (Chrysiogenes arsenatis, Desulfurispira natronophila, Desulfurispirillum alkaliphilum)
- Cyanobacteria, also known as the blue-green algae
- Deinococcus-Thermus, Deinococcus radiodurans and Thermus aquaticus are "commonly known" species of this phyla
- Elusimicrobia, formerly candidate division Thermite Group 1
- Firmicutes, Low-G+C Gram positive species, such as the spore-formers Bacilli (aerobic) and Clostridia (anaerobic)
- Lentisphaerae, formerly clade VadinBE97
- Planctomycetes ANo ito?
- Proteobacteria, the most known phyla, containing species such as Escherichia coli or Pseudomonas aeruginosa
- Spirochaetes, species include Borrelia burgdorferi, which causes Lyme disease
- Tenericutes, alternatively class Mollicutes in phylum Firmicutes (notable genus: Mycoplasma)
- Thermotogae, deep branching
Archaeal Phyla/Division/Kingdoms 
- Crenarchaeota, Second most common archaeal phylum
- Euryarchaeota, most common archaeal phylum
- Nanoarchaeota, ultra-small symbiotes
See also 
- ^ The term was coined by Haeckel from Greek φῦλον phylon, "race, stock," related to φυλή phyle, "tribe, clan."
- ^ "Life sciences". The American Heritage New Dictionary of Cultural Literacy (third ed.). Houghton Mifflin Company. 2005. Retrieved 2008-10-04. "Phyla in the plant kingdom are frequently called divisions."
- ^ Berg, Linda R. (2007-03-02). Introductory Botany: Plants, People, and the Environment (2 ed.). Cengage Learning. p. 15. ISBN 9780534466695. Retrieved 23 July 2012.
- ^ Collins AG, Valentine JW (2001). "Defining phyla: evolutionary pathways to metazoan body plans." Evol. Dev. 3: 432-442.
- ^ Naik, V. N. (1984). Taxonomy of Angiosperms. Tata McGraw Hill, New Delhi, p. 27.
- ^ Valentine, James W. (2004). On the Origin of Phyla. Chicago: University Of Chicago Press. p. 7. ISBN 0-226-84548-6. "Classifications of organisms in hierarchical systems were in use by the seventeenth and eighteenth centuries. Usually organisms were grouped according to their what? 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. (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. PMID 8865666.
- ^ Budd, G.E. (1998). "Arthropod body-plan evolution in the Cambrian with an example from anomalocaridid muscle". Lethaia (Blackwell Synergy) 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.
- ^ Feldkamp, S. (2002) Modern Biology. Holt, Rinehart, and Winston, USA. (pp. 725)
- ^ Species Register. "Flatworms — Phylum Platyhelminthes". Marine Discovery Centres. Retrieved 2007-04-09.
- ^ "Kingdom Plantae Tree of Life".
- ^ J.P. Euzéby. "List of Prokaryotic names with Standing in Nomenclature: Phyla". Retrieved 30 December 2010.
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