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The hierarchy of biological classification's eight major taxonomic ranks. A kingdom contains one or more phyla. Intermediate minor rankings are not shown. Biological classification L Pengo vflip.svg DomainKingdomClassOrderFamily
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 ( /ˈfləm/ ; plural: 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 contains about 31 phyla, the plant kingdom Plantae contains about 14 phyla, 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.


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"). [4] [5] Haeckel noted that species constantly evolved into new species that seemed to retain few consistent features among themselves and therefore few features that distinguished them as a group ("a self-contained unity"). "Wohl aber ist eine solche reale und vollkommen abgeschlossene Einheit die Summe aller Species, welche aus einer und derselben gemeinschaftlichen Stammform allmählig sich entwickelt haben, wie z. B. alle Wirbelthiere. Diese Summe nennen wir Stamm (Phylon)." which translates as: However, perhaps such a real and completely self-contained unity is the aggregate of all species which have gradually evolved from one and the same common original form, as, for example, all vertebrates. We name this aggregate [a] Stamm [i.e., race] (Phylon). 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] [6] The definitions of zoological phyla have changed from their origins in the six Linnaean classes and the four embranchements of Georges Cuvier. [7]

Informally, phyla can be thought of as groupings of organisms based on general specialization of body plan. [8] 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). [9] 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 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. [9] 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). [10] 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. [11]

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. [9]

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. [9] 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. [9] 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. [12]

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. [13]

Known phyla


Total numbers are estimates; figures from different authors vary wildly, not least because some are based on described species, [14] 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. [15]

Protostome Bilateria Nephrozoa
Basal/disputed Non-Bilateria
PhylumMeaningCommon nameDistinguishing characteristicTaxa described
Annelida Little ring [16] :306Segmented wormsMultiple circular segments22,000 + extant
Agmata FragmentedAgmatesCalcareous conical shells5 species, extinct
Archaeocyatha Ancient cupsArchaeocyathidsAn extinct taxon of sponge-grade, reef-building organisms living in warm tropical and subtropical waters during the Early Cambrian.3 known classes (Extinct)
Arthropoda Jointed footArthropodsSegmented bodies and jointed limbs, with Chitin exoskeleton 1,250,000+ extant; [14] 20,000+ extinct
Brachiopoda Arm foot [16] :336Lampshells [16] :336 Lophophore and pedicle 300-500 extant; 12,000+ extinct
Bryozoa (Ectoprocta)Moss animalsMoss animals, sea mats, ectoprocts [16] :332Lophophore, no pedicle, ciliated tentacles, anus outside ring of cilia6,000 extant [14]
Chaetognatha Longhair jawArrow worms [16] :342 Chitinous spines either side of head, finsapprox. 100 extant
Chordata With a cordChordatesHollow dorsal nerve cord, notochord, pharyngeal slits, endostyle, post-anal tail approx. 55,000+ [14]
Cnidaria Stinging nettleCnidarians Nematocysts (stinging cells)approx. 16,000 [14]
Ctenophora Comb bearerComb jellies [16] :256Eight "comb rows" of fused ciliaapprox. 100-150 extant
Cycliophora Wheel carryingSymbionCircular mouth surrounded by small cilia, sac-like bodies3+
Echinodermata Spiny skinEchinoderms [16] :348Fivefold radial symmetry in living forms, mesodermal calcified spinesapprox. 7,500 extant; [14] approx. 13,000 extinct
Entoprocta Inside anus [16] :292Goblet wormsAnus inside ring of ciliaapprox. 150
Gastrotricha Hairy stomach [16] :288Gastrotrich wormsTwo terminal adhesive tubesapprox. 690
Gnathostomulida Jaw orificeJaw worms [16] :260Tiny worms related to rotifers with no body cavityapprox. 100
Hemichordata Half cord [16] :344Acorn worms, hemichordates Stomochord in collar, pharyngeal slits approx. 130 extant
Kinorhyncha Motion snoutMud dragonsEleven segments, each with a dorsal plateapprox. 150
Loricifera Corset bearerBrush headsUmbrella-like scales at each endapprox. 122
Micrognathozoa Tiny jaw animalsLimnognathia Accordion-like extensible thorax 1
Medusoid Jellyfish-likeMedusoidsThese are extinct creatures described as jellyfish-like and inhabited the late Precambrian, Ediacaran and early Cambrian.18 genera, extinct
Mollusca Soft [16] :320Mollusks / molluscsMuscular foot and mantle round shell85,000+ extant; [14] 80,000+ extinct [17]
Nematoda Thread likeRound worms, thread worms [16] :274Round cross section, keratin cuticle 25,000 [14]
Nematomorpha Thread form [16] :276Horsehair worms, gordian worms [16] :276Long, thin parasitic worms closely related to nematodesapprox. 320
Nemertea A sea nymph [16] :270Ribbon worms, rhynchocoela [16] :270Unsegmented worms, with a proboscis housed in a cavity derived from the coelom called the rhynchocoelapprox. 1,200
Onychophora Claw bearerVelvet worms [16] :328Worm-like animal with legs tipped by chitinous clawsapprox. 200 extant
Petalonamae Shaped like leavesNoAn extinct phylum from the Ediacaran. They are bottom-dwelling and immobile, shaped like leaves (frondomorphs), feathers or spindles.3 classes, extinct
Phoronida Zeus's mistressHorseshoe wormsU-shaped gut11
Placozoa Plate animalsTrichoplaxes [16] :242Differentiated top and bottom surfaces, two ciliated cell layers, amoeboid fiber cells in between3
Platyhelminthes Flat worm [16] :262Flatworms [16] :262Flattened worms with no body cavity. Many are parasitic.approx. 29,500 [14]
Porifera Pore bearerSponges [16] :246Perforated interior wall, simplest of all known animals10,800 extant [14]
Priapulida Little Priapus Penis wormsPenis-shaped wormsapprox. 20
Proarticulata Before articulatesProarticulatesAn extinct group of mattress-like organisms that display "glide symmetry." Found during the Ediacaran.3 classes, extinct
Rhombozoa (Dicyemida)Lozenge animalRhombozoans [16] :264Single anteroposterior axial celled endoparasites, surrounded by ciliated cells100+
Rotifera Wheel bearerRotifers [16] :282Anterior crown of ciliaapprox. 2,000 [14]
Saccorhytida Saccus : "pocket" and "wrinkle"SaccorhytusSaccorhytus is only about 1 mm (1.3 mm) in size and is characterized by a spherical or hemispherical body with a prominent mouth. Its body is covered by a thick but flexible cuticle. It has a nodule above its mouth. Around its body are 8 openings in a truncated cone with radial folds.1 species, extinct
Tardigrada Slow stepWater bears, Moss pigletsMicroscopic relatives of the arthropods, with a four segmented body and head1,000
Trilobozoa Three-lobed animalTrilobozoanA taxon of mostly discoidal organisms exhibiting tricentric symmetry. All are Ediacaran-aged18 genera, extinct
Vetulicolia Ancient dwellerVetulicolianMight possibly be a subphylum of the chordates. Their body consists of two parts: a large front part and covered with a large "mouth" and a hundred round objects on each side that have been interpreted as gills - or at least openings in the vicinity of the animal. Their posterior pharynx consists of 7 segments.15 species, extinct
Xenacoelomorpha Strange hollow formSubphylum Acoelomorpha and xenoturbellidaSmall, simple animals. Bilaterian, but lacking typical bilaterian structures such as gut cavities, anuses, and circulatory systems [18] 400+
Total: 401,525,000 [14]


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, [19] 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 Monilophyta, [20] while others place them both in Monilophyta, as shown below. The division Pinophyta may be used for all gymnosperms (i.e. including cycads, ginkgos and gnetophytes), [21] 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. [22]

Land plants Viridiplantae
Green algae
Other algae (Biliphyta) [19]
DivisionMeaningCommon nameDistinguishing characteristicsSpecies described
Anthocerotophyta [23] Anthoceros -like plantsHornwortsHorn-shaped sporophytes, no vascular system100-300+
Bryophyta [23] Bryum -like plants, moss plantsMossesPersistent unbranched sporophytes, no vascular systemapprox. 12,000
Charophyta Chara -like plantsCharophytesapprox. 1,000
Chlorophyta (Yellow-)green plants [16] :200Chlorophytesapprox. 7,000
Cycadophyta [24] Cycas -like plants, palm-like plantsCycadsSeeds, crown of compound leavesapprox. 100-200
Ginkgophyta [25] Ginkgo -like plantsGinkgo, maidenhair treeSeeds not protected by fruit (single living species)only 1 extant; 50+ extinct
Glaucophyta Blue-green plantsGlaucophytes15
Gnetophyta [26] Gnetum -like plantsGnetophytesSeeds and woody vascular system with vesselsapprox. 70
Lycopodiophyta, [21]

Lycophyta [27]

Lycopodium -like plants

Wolf plants

Clubmosses & spikemosses Microphyll leaves, vascular system1,290 extant
Magnoliophyta Magnolia -like plantsFlowering plants, angiospermsFlowers and fruit, vascular system with vessels300,000
Marchantiophyta, [28]

Hepatophyta [23]

Marchantia -like plants

Liver plants

LiverwortsEphemeral unbranched sporophytes, no vascular systemapprox. 9,000
Polypodiophyta ,


Polypodium -like plants
Ferns Megaphyll leaves, vascular systemapprox. 10,560
Pinophyta, [21]

Coniferophyta [29]

Pinus -like plants

Cone-bearing plant

ConifersCones containing seeds and wood composed of tracheids629 extant
Rhodophyta Rose plantsRed algaeUse phycobiliproteins as accessory pigments.approx. 7,000
Total: 14


DivisionMeaningCommon nameDistinguishing characteristicsSpecies described
Ascomycota Bladder fungus [16] :396Ascomycetes, [16] :396 sac fungiTend to have fruiting bodies (ascocarp). [30] Filamentous, producing hyphae separated by septa. Can reproduce asexually. [31] 30,000
Basidiomycota Small base fungus [16] :402Basidiomycetes, [16] :402 club fungiBracket fungi, toadstools, smuts and rust. Sexual reproduction. [32] 31,515
Blastocladiomycota Offshoot branch fungus [33] BlastocladsLess than 200
Chytridiomycota Little cooking pot fungus [34] ChytridsPredominantly Aquatic saprotrophic or parasitic. Have a posterior flagellum. Tend to be single celled but can also be multicellular. [35] [36] [37] 1000+
Glomeromycota Ball of yarn fungus [16] :394Glomeromycetes, AM fungi [16] :394Mainly arbuscular mycorrhizae present, terrestrial with a small presence on wetlands. Reproduction is asexual but requires plant roots. [32] 284
Microsporidia Small seeds [38] Microsporans [16] :3901400
Neocallimastigomycota New beautiful whip fungus [39] NeocallimastigomycetesPredominantly located in digestive tract of herbivorous animals. Anaerobic, terrestrial and aquatic. [40] approx. 20 [41]
Zygomycota Pair fungus [16] :392Zygomycetes [16] :392Most are saprobes and reproduce sexually and asexually. [40] aprox. 1060
Total: 8

Phylum Microsporidia is generally included in kingdom Fungi, though its exact relations remain uncertain, [42] and it is considered a protozoan by the International Society of Protistologists [43] (see Protista, below). Molecular analysis of Zygomycota has found it to be polyphyletic (its members do not share an immediate ancestor), [44] 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. [42]


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. [16] :120 Protista is a polyphyletic taxon, [45] 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. [46]

Protist taxonomy has long been unstable, [47] 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, [48] adapted from the system used by the International Society of Protistologists. [43]

Phylum/DivisionMeaningCommon nameDistinguishing characteristicsExampleSpecies described
Amoebozoa Amorphous animalAmoebasPresence of pseudopodia Amoeba 2400
Bigyra Two rings
Choanozoa Funnel animalPresence of a colar of microvilli surrounding a flagellum 125
Ciliophora Cilia bearerCiliatesPresence of multiple cilia and a cytostome Paramecium4500
Cryptista Hidden
Euglenozoa True eye animalEuglena800
Foraminifera Hole bearersForamsComplex shells with one or more chambersForams10000, 50000 extinct
Loukozoa Groove animal
Metamonada Middle single-celled organismsGiardia
Microsporidia Small spore
Myzozoa Suckling animal1555+
Ochrophyta Yellow plantDiatoms
Oomycota Egg fungus [16] :184Oomycetes
Radiozoa Ray animalRadiolarians
Sarcomastigophora Flesh and whip bearer
Total: 19

The Catalogue of Life includes Rhodophyta and Glaucophyta in kingdom Plantae, [48] but other systems consider these phyla part of Protista. [49]


Currently there are bacterial 40 phyla (not including "Cyanobacteria") that have been validly published according to the Bacteriological Code [50]

  1. Acidobacteriota, phenotypically diverse and mostly uncultured
  2. Actinomycetota, High-G+C Gram positive species
  3. Aquificota, deep-branching
  4. Armatimonadota
  5. Atribacterota
  6. Bacillota, Low-G+C Gram positive species, such as the spore-formers Bacilli (aerobic) and Clostridia (anaerobic)
  7. Bacteroidota
  8. Balneolota
  9. Bdellovibrionota
  10. Caldisericota, formerly candidate division OP5, Caldisericum exile is the sole representative
  11. Calditrichota
  12. Campylobacterota
  13. Chlamydiota
  14. Chlorobiota, green sulphur bacteria
  15. Chloroflexota, green non-sulphur bacteria
  16. Chrysiogenota, only 3 genera (Chrysiogenes arsenatis, Desulfurispira natronophila, Desulfurispirillum alkaliphilum)
  17. Coprothermobacterota
  18. Deferribacterota
  19. Deinococcota, Deinococcus radiodurans and Thermus aquaticus are "commonly known" species of this phyla
  20. Dictyoglomota
  21. Elusimicrobiota, formerly candidate division Thermite Group 1
  22. Fibrobacterota
  23. Fusobacteriota
  24. Gemmatimonadota
  25. Ignavibacteriota
  26. Kiritimatiellota
  27. Lentisphaerota, formerly clade VadinBE97
  28. Mycoplasmatota, notable genus: Mycoplasma
  29. Myxococcota
  30. Nitrospinota
  31. Nitrospirota
  32. Planctomycetota
  33. Pseudomonadota, the most well-known phylum, containing species such as Escherichia coli or Pseudomonas aeruginosa
  34. Rhodothermota
  35. Spirochaetota, species include Borrelia burgdorferi , which causes Lyme disease
  36. Synergistota
  37. Thermodesulfobacteriota
  38. Thermomicrobiota
  39. Thermotogota, deep-branching
  40. Verrucomicrobiota


Currently there are 2 phyla that have been validly published according to the Bacteriological Code [50]

  1. Nitrososphaerota
  2. Thermoproteota, second most common archaeal phylum

Other phyla that have been proposed, but not validly named, include:

  1. "Euryarchaeota", most common archaeal phylum
  2. "Korarchaeota"
  3. "Nanoarchaeota", ultra-small symbiotes, single known species

See also


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    Linnaean taxonomy Rank based classification system for organisms

    Linnaean taxonomy can mean either of two related concepts:

    1. the particular form of biological classification (taxonomy) set up by Carl Linnaeus, as set forth in his Systema Naturae (1735) and subsequent works. In the taxonomy of Linnaeus there are three kingdoms, divided into classes, and they, in turn, 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-based scientific classification. This term is especially used as opposed to cladistic systematics, which groups organisms into clades. It is attributed to Linnaeus, although he neither invented the concept of ranked classification 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.
    Taxonomy (biology) Science of naming, defining and classifying organisms

    In biology, taxonomy is the scientific study of naming, defining (circumscribing) and classifying groups of biological organisms based on shared characteristics. Organisms are grouped into taxa and these groups are given a taxonomic rank; groups of a given rank can be aggregated to form a more inclusive group of higher rank, thus creating a taxonomic hierarchy. The principal ranks in modern use are domain, kingdom, phylum, class, order, family, genus, and species. The Swedish botanist Carl Linnaeus is regarded as the founder of the current system of taxonomy, as he developed a ranked system known as Linnaean taxonomy for categorizing organisms and binominal nomenclature for naming organisms.

    In biology, a kingdom is the second highest taxonomic rank, just below domain. Kingdoms are divided into smaller groups called phyla. Traditionally, some textbooks from the United States and Canada used a system of six kingdoms while textbooks in Great Britain, India, Greece, Brazil and other countries use five kingdoms only. Some recent classifications based on modern cladistics have explicitly abandoned the term kingdom, noting that some traditional kingdoms are not monophyletic, meaning that they do not consist of all the descendants of a common ancestor. The terms flora, fauna, and, in the 21st century, funga are also used for life present in a particular region or time.

    In biological classification, class is a taxonomic rank, as well as a taxonomic unit, a taxon, in that rank. Other well-known ranks in descending order of size are life, domain, kingdom, phylum, order, family, genus, and species, with class fitting between phylum and order.

    Three-domain system Hypothesis for classification of life

    The three-domain system is a biological classification introduced by Carl Woese, Otto Kandler and Mark Wheelis in 1990 that divides cellular life forms into three domains, namely Archaea, Bacteria, and Eukaryote or Eukarya. The key difference from earlier classifications such as the two-empire system and the five-kingdom classification is the splitting of archaea from bacteria as completely different organism. It has been challenged by the two-domain system that divides organisms into Bacteria and Archaea only, as eukaryotes are considered as one group of archaea.

    Chytridiomycota Division of fungi

    Chytridiomycota are a division of zoosporic organisms in the kingdom Fungi, informally known as chytrids. The name is derived from the Ancient Greek χυτρίδιον, meaning "little pot", describing the structure containing unreleased zoöspores. Chytrids are one of the early diverging fungal lineages, and their membership in kingdom Fungi is demonstrated with chitin cell walls, a posterior whiplash flagellum, absorptive nutrition, use of glycogen as an energy storage compound, and synthesis of lysine by the α-amino adipic acid (AAA) pathway.

    Taxon Group of one or more populations of an organism or organisms which have distinguishing characteristics in common

    In biology, a taxon is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular name and given a particular ranking, especially if and when it is accepted or becomes established. It is very common, however, for taxonomists to remain at odds over what belongs to a taxon and the criteria used for inclusion. If a taxon is given a formal scientific name, its use is then governed by one of the nomenclature codes specifying which scientific name is correct for a particular grouping.

    Chromista Eukaryotic biological kingdom

    Chromista is a biological kingdom consisting of single-celled and multicellular eukaryotic species that share similar features in their photosynthetic organelles (plastids). It includes all protists whose plastids contain chlorophyll c, such as some algae, diatoms, oomycetes, and protozoans. It is a polyphyletic group whose members independently arose as a separate evolutionary group from the common ancestor of all eukaryotes. As it is assumed the last common ancestor already possessed chloroplasts of red algal origin, the non-photosynthetic forms evolved from ancestors able to perform photosynthesis. Their plastids are surrounded by four membranes, and are believed to have been acquired from some red algae.

    Thomas Cavalier-Smith British evolutionary biologist

    Thomas (Tom) Cavalier-Smith, FRS, FRSC, NERC Professorial Fellow, was a Professor of Evolutionary Biology in the Department of Zoology, at the University of Oxford.

    Body plan Set of morphological features common to members of a phylum of animals

    A body plan, Bauplan, or ground plan is a set of morphological features common to many members of a phylum of animals. The vertebrates share one body plan, while invertebrates have many.

    Tree of life (biology) Metaphor for the relationship between species of organisms

    The tree of life or universal tree of life is a metaphor, model and research tool used to explore the evolution of life and describe the relationships between organisms, both living and extinct, as described in a famous passage in Charles Darwin's On the Origin of Species (1859).

    The affinities of all the beings of the same class have sometimes been represented by a great tree. I believe this simile largely speaks the truth.

    Phylogenetic nomenclature is a method of nomenclature for taxa in biology that uses phylogenetic definitions for taxon names as explained below. This contrasts with the traditional approach, in which taxon names are defined by a type, which can be a specimen or a taxon of lower rank, and a description in words. Phylogenetic nomenclature is currently regulated by the International Code of Phylogenetic Nomenclature (PhyloCode).

    Blastocladiomycota Phylum of flagellated fungi

    Blastocladiomycota is one of the currently recognized phyla within the kingdom Fungi. Blastocladiomycota was originally the order Blastocladiales within the phylum Chytridiomycota until molecular and zoospore ultrastructural characters were used to demonstrate it was not monophyletic with Chytridiomycota. The order was first erected by Petersen for a single genus, Blastocladia, which was originally considered a member of the oomycetes. Accordingly, members of Blastocladiomycota are often referred to colloquially as "chytrids." However, some feel "chytrid" should refer only to members of Chytridiomycota. Thus, members of Blastocladiomyota are commonly called "blastoclads" by mycologists. Alternatively, members of Blastocladiomycota, Chytridiomycota, and Neocallimastigomycota lumped together as the zoosporic true fungi. Blastocladiomycota contains 5 families and approximately 12 genera. This early diverging branch of kingdom Fungi is the first to exhibit alternation of generations. As well, two (once) popular model organisms—Allomyces macrogynus and Blastocladiella emersonii—belong to this phylum.

    Taxonomic rank Level in a taxonomic hierarchy

    In biological classification, taxonomic rank is the relative level of a group of organisms in a taxonomic hierarchy. Examples of taxonomic ranks are species, genus, family, order, class, phylum, kingdom, domain, etc.

    Marine invertebrates Marine animals without a vertebrate column

    Marine invertebrates are the invertebrates that live in marine habitats. Invertebrate is a blanket term that includes all animals apart from the vertebrate members of the chordate phylum. Invertebrates lack a vertebral column, and some have evolved a shell or a hard exoskeleton. As on land and in the air, marine invertebrates have a large variety of body plans, and have been categorised into over 30 phyla. They make up most of the macroscopic life in the oceans.

    Monera Biological kingdom that contains unicellular organisms with a prokaryotic cell organization

    Monera (/məˈnɪərə/) is a biological kingdom that is made up of prokaryotes. As such, it is composed of single-celled organisms that lack a true nucleus.

    Protist Eukaryotic organisms that are neither animals, plants nor fungi

    A protist is any eukaryotic organism that is not an animal, plant, or fungus. While it is likely that protists share a common ancestor, the exclusion of other eukaryotes means that protists do not form a natural group, or clade. Therefore, some protists may be more closely related to animals, plants, or fungi than they are to other protists; however, like the groups algae, invertebrates, and protozoans, the biological category protist is used for convenience. Others classify any unicellular eukaryotic microorganism as a protist. The study of protists is termed protistology.

    Protozoa Single-celled eukaryotic organisms that feed on organic matter

    Protozoa is an informal term for a group of single-celled eukaryotes, either free-living or parasitic, that feed on organic matter such as other microorganisms or organic tissues and debris. Historically, protozoans were regarded as "one-celled animals", because they often possess animal-like behaviours, such as motility and predation, and lack a cell wall, as found in plants and many algae.

    Bacterial taxonomy is the taxonomy, i.e. the rank-based classification, of bacteria.

    The biological classification system of life introduced by British zoologist Thomas Cavalier-Smith involves systematic arrangements of all life forms on earth. Following and improving the classification systems introduced by Carl Linnaeus, Ernst Haeckel, Robert Whittaker, and Carl Woese, Cavalier-Smith's classification attempts to incorporate the latest developments in taxonomy. His classification has been a major foundation in modern taxonomy, particularly with revisions and reorganisations of kingdoms and phyla.


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