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In biological taxonomy, a 'phylum' (Greek plural: 'phyla') is a taxon in the rank below kingdom and above class. "Phylum" is adopted from the Greek ''phylai'', the clan-based voting groups in Greek city-states. Phyla represent the largest generally accepted groupings of animals and other living things with certain evolutionary traits, although the phyla themselves may sometimes be grouped into ''superphyla'' (e.g. Ecdysozoa with eight phyla, including arthropods and roundworms; and Deuterostomia with the echinoderms, chordates, hemichordates and arrow worms). Informally, phyla can be thought of as grouping animals based on general body plan^[1]; this is morphological grouping. Thus despite the seemingly different ''external'' appearances of organisms, they are classified into phyla based on their ''internal'' organizations^[2]. For example, though seemingly divergent, spiders and crabs both belong to Arthropoda, whereas earthworms and tapeworms, similar in shape, are from Annelida and Platyhelminthes, respectively. Although the International Code of Botanical Nomenclature allows the use of the term "Phylum" in reference to plants, the term "Division" is almost always used by botanists.
The best known animal phyla are the Mollusca, Porifera, Cnidaria, Platyhelminthes, Nematoda, Annelida, Arthropoda, Echinodermata, and Chordata, the phylum to which humans belong. Although there are approximately 35 phyla, these nine include the majority of the species. Many phyla are exclusively marine, and only one phylum is entirely absent from the world's oceans: the Onychophora or velvet worms. The most recently discovered phylum is Cycliophora^[3] found in 1993; only three phyla were discovered in the last century.
The Cambrian explosion was a great flowering of life forms that occurred between roughly 530 and 520 million years ago; Fossils, molecules and embryos: new perspectives on the Cambrian explosion, Valentine, J.W., , , Development, 1999 during this time organisms similar to, but not strictly members of, modern phyla existed; A critical reappraisal of the fossil record of the bilaterian phyla, Budd, G.E., , , Biological Reviews, 2000 whilst some appear to be represented in the Ediacaran biota, it remains a matter of debate whether all phyla existed prior to the explosion. Over time the roles among different phyla have varied. For instance, during the Cambrian, the dominant megafauna, or large animals, were arthropods, whereas now the megafauna is dominated by vertebrates (chordata).^[4] The arthropods are still by far the most dominant phylum.

Contents

List of animal phyla

Groups formerly ranked as phyla

List of plant divisions

List of fungi divisions

See also

References

External links

List of animal phyla

'Phylum'	'Meaning'	'Group'	'Distinguishing characteristics'	'Species described'
Acanthocephala	Thorny head	Thorny-headed worms	Reversible spiny proboscis	about 1,151
Acoelomorpha	Without gut	Acoels	No mouth or alimentary canal
Annelida	Little ring	Segmented worms	Multiple circular segments	about 15,000 modern
Arthropoda	Jointed foot	Arthropods	Chitin exoskeleton	1,134,000+
Brachiopoda	Arm foot	Lamp shells	Lophophore and pedicle	between 300 and 500 extant
Bryozoa	Moss animals	Moss animals, sea mats	Lophophore, no pedicle, ciliated tentacles	about 5,000 living species
Chaetognatha	Longhair jaw	Arrow worms	Chitinous spines either side of head, fins	about 100 modern species
Chordata	Cord	Chordates	Hollow dorsal nervous chord	about 100,000+
Cnidaria	Stinging nettle	Coelenterates	Nematocysts (stinging cells)	about 11,000
Ctenophora	Comb bearer	Comb jellies	Eight "comb rows" of fused cilia	about 100 modern species
Cycliophora	Wheel carrying	''Symbion''	Circular mouth surrounded by small cilia	at least 3
Echinodermata	Spiny skin	Echinoderms	Five-fold radial symmetry, mesodermal calcified spines	about 7,000 living species and 13,000 extinct ones
Echiura	Spine tail	Spoon worms	Set of hooks at posterior end	about 140
Entoprocta	Inside anus	Goblet worm	Anus inside ring of cilia	about 150
Gastrotricha	Hair stomach	Meiofauna	Two terminal adhesive tubes	about 690
Gnathostomulida	Jaw orifice	Jaw worms		about 100
Hemichordata	Half cord	Acorn worms	Stomochord in collar	about 100 living species
Kinorhyncha	Motion snout	Mud dragons	Eleven segments, each with a dorsal plate	about 150
Loricifera	Corset bearer	Brush heads	Umbrella-like scales at each end	about 122
Mesozoa	Middle animals	Mesozoans	Somatoderm of ciliated cells surrounding reproductive cell(s)
Micrognathozoa	Tiny jaw animals	—	Accordion like extensible thorax	1
Mollusca	Thin shell	Mollusks / molluscs	Muscular foot and mantle round shell	112,000[5]
Myxozoa	Slime animals		Polar capsules resembling nematocysts	13,000+
Nematoda	Thread like	Round worms	Round cross section, keratin cuticle	80 000 - 1 million
Nematomorpha	Thread form	Horsehair worms		about 320
Nemertea	A sea nymph	Ribbon worms		about 1200
Onychophora	Claw bearer	Velvet worms	Legs tipped by chitinous claws	about 200 modern
Orthonectida	Straight swim			about 20
Phoronida	Zeus' mistress	Horseshoe worms	U-shaped gut	20
Placozoa	Plate animals			1
Platyhelminthes	Flat worms	Flat worms		about 25,000[6]
Porifera	Pore bearer	Sponges	Perforated interior wall	over 5,000 modern
Priapulida	Penis	Priapulid worms	Retractable proboscis surrounded by papillae	17
Rhombozoa	Lozenge animal	—	Single axial cell surrounded by ciliated cells	75
Rotifera	Wheel bearer	Rotifers	Anterior crown of cilia	about 2000
Sipuncula	Small tube	Peanut worms	Mouth surrounded by invertible tentacles	144-320
Tardigrada	Slow step	Water bears	Four segmented body and head	1,000+
Xenoturbellida	Strange flatworm	—	Ciliated deuterostome	2
'TOTAL'				'2,400,000+'

Groups formerly ranked as phyla

Name as phylum	Common name	Current consensus
Craniata	—	Subgroup of phylum Chordata; perhaps synonymous with Vertebrata.
Cephalochordata	Lancelets	Subphylum of phylum Chordata
Cephalorhyncha	—	Superphylum Scalidophora.
Enterepneusta	Acorn worms	Class of phylum Hemichordata.
Pentastomida	Tongue worms	Subclass of Maxillopoda of phylum Arthropoda.
Pogonophora	Beard worms	Part of family Siboglinidae of phylum Annelida.
Pterobranchia	—	Class of phylum Hemichordata.
Symplasma	Glass sponges	Class Hexactinellida of phylum Porifera.
Urochordata	Tunicates	Subphylum of phylum Chordata.
Vestimentifera	Vent worms	Part of family Siboglinidae of phylum Annelida.

List of plant divisions

'Division'	'Meaning'	'Common name'	'Distinguishing characteristics'
Anthocerotophyta	Flower-horn plants	Hornworts	Horn-shaped sporophytes, no vascular system
Bryophyta	Moss plants	Mosses	Persistent unbranched sporophytes, no vascular system
Marchantiophyta	''Marchantia'' plants	Liverworts	Ephemeral unbranched sporophytes, no vascular system
Lycopodiophyta	Wolf foot plants	Clubmosses & Spikemosses	Microphyll leaves, vascular system
Pteridophyta	Fern plants	Ferns & Horsetails	Prothallus gametophytes, vascular system
Pteridospermatophyta	fern with seeds plant	Seed ferns	only known from fossils, mostly Devonian, ranking in dispute[7]
Pinophyta	Sap/pitch plants	Conifers	Cones containing seeds
Cycadophyta	Palm plants	Cycads	Seeds, crown of compound leaves
Ginkgophyta	Ginkgo plants	Ginkgo, Maidenhair	Seeds not protected by fruit (single species)
Gnetophyta		Gnetophytes	Seeds and woody vascular system
Anthophyta	Flower plant	Flowering plants	Producing flowers and fruit (or close relatives)

List of fungi divisions

'Phylum'	'Meaning'	'Common name'	'Distinguishing characteristics'
Chytridiomycota	Little pot mushroom	Chytrids	Cellulose in cell walls, flagellated gametes
Deuteromycota	Second mushroom	Imperfect fungi	Only reproduce asexually
Zygomycota	Yoke mushroom	Zygomycetes	Blend gametangia to form a zygosporangium
Glomeromycota	Ball mushroom	None	Form arbuscular mycorrhizae with plants
Ascomycota	Bag/Wineskin Mushroom	Sac fungi	Produce spores in an 'ascus'
Basidiomycota	Basidium Mushroom	None	Produce spores from a 'basidium'

See also

★ Cladistics

★ Phylogenetics

★ Systematics

★ Taxonomy

References

1. On the Origin of Phyla, , James W., Valentine, University Of Chicago Press, 2004, 0226845486 "Classifications of organisms in hierarchical systems were in use by the seventeenth and eighteenth centuries. 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."
2. In the blink of an eye: How vision kick-started the big bang of evolution, , Andrew, Parker, Free Press, 2003, 0743257332 "The job of an evolutionary biologist is to make sense of the conflicting diversity of form - there is not always a relationship between internal and external parts. Early in the history of the subject, it became obvious that internal organisations were generally more important to the higher classification of animals than are external shapes. The internal organisation puts general restrictions on how an animal can exchange gases, obtain nutrients and reproduce."
3. "...when a new animal species is discovered, no matter how unusual, it can normally be classified into a known group of creatures with the same body plan or phylum. Although there are 1.5 million plus known species in the world, they can all be classified into 35 or so phyla. These include the chordates (eg the vertebrates such as man), molluscs (snails) and arthropods (jointed limbed e.g. insects). However, S.pandora was so unusual that it could not be classified into any of the existing phyla, and a new one was suggested called Cycliophora" [1] (URL accessed on July 5, 2006)
4. "The Cambrian Explosion ... The organisms range from the prokaryotic cyanobacteria to eukaryotic green and red algae, to sponges, brachiopods, priapulids, annelids, and many different arthropod groups, as well as echinoderms and possibly one of the first chordates." [2] (URL accessed on July 5, 2006)
5. Feldkamp, S. (2002) ''Modern Biology''. Holt, Rinehart, and Winston, USA. (pp. 725)
6. Flatworms - Phylum Platyhelminthes
7. "Kingdon Plantae Tree of Life"

External links

★ Major Phyla Of Animals

★ Are phyla "real"? Is there really a well-defined "number of animal phyla" extant and in the fossil record?
Etymology:

★ American Heritage Dictionary: New Latin phylum, from Greek phūlon, class.

★ Online Etymological Dictionary: from Gk. phylon "race, stock," related to phyle "tribe, clan," and phylein "bring forth" of physikos "pertaining to nature," from physis "nature"