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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 approximately 31 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.


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
PhylumMeaningCommon nameDistinguishing characteristicSpecies described
Annelida Little ring [16] :306Segmented wormsMultiple circular segments22,000 + extant
Agmata FragmentedAgmates
Archaeocyatha Animals with collarsNoAn extinct taxon without stalks, living near corals and 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
Ivesheadiomorpha NoNoPoorly preserved biological remains of ediacaric fossils4
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] :270Aquatic worms, with some that can grow to great lengthsapprox. 1,200
Onychophora Claw bearerVelvet worms [16] :328Worm-like animal with legs tipped by chitinous clawsapprox. 200 extant
Petalonamae Shaped like leavesNoAn extinct phylum representing the Ediacaran population. They are bottom-dwelling and immobile, shaped like leaves (frondomorphs), feathers or spindles.File:Swartpuntiagermsi.png3 classes, extinct
Proarticulata Before articulatesProarticulatesAn extinct, bilaterally symmetric fauna known from chemistries found in Ediacaran (Vendia) marine sediments.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 know animals10,800 extant [14]
Priapulida Little Priapus Penis wormsPenis-shaped wormsapprox. 20
Rhombozoa (Dicyemida)Lozenge animalRhombozoans [16] :264Single anteroposterior axial cell 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 extinct organisms exhibiting tricentric symmetry.18 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 29 phyla accepted by List of Prokaryotic names with Standing in Nomenclature (LPSN) [50]

  1. Acidobacteria, phenotypically diverse and mostly uncultured
  2. Actinobacteria, High-G+C Gram positive species
  3. Aquificae, only 14 thermophilic genera, deep branching
  4. Armatimonadetes
  5. Bacteroidetes
  6. Caldiserica, formerly candidate division OP5, Caldisericum exile is the sole representative
  7. Chlamydiae, only 6 genera
  8. Chlorobi, only 7 genera, green sulphur bacteria
  9. Chloroflexi, green non-sulphur bacteria
  10. Chrysiogenetes, only 3 genera (Chrysiogenes arsenatis, Desulfurispira natronophila, Desulfurispirillum alkaliphilum)
  11. Cyanobacteria, also known as the blue-green algae
  12. Deferribacteres
  13. Deinococcus-Thermus, Deinococcus radiodurans and Thermus aquaticus are "commonly known" species of this phyla
  14. Dictyoglomi
  15. Elusimicrobia, formerly candidate division Thermite Group 1
  16. Fibrobacteres
  17. Firmicutes, Low-G+C Gram positive species, such as the spore-formers Bacilli (aerobic) and Clostridia (anaerobic)
  18. Fusobacteria
  19. Gemmatimonadetes
  20. Lentisphaerae, formerly clade VadinBE97
  21. Nitrospira
  22. Planctomycetes
  23. Proteobacteria, the most known phyla, containing species such as Escherichia coli or Pseudomonas aeruginosa
  24. Spirochaetes, species include Borrelia burgdorferi , which causes Lyme disease
  25. Synergistetes
  26. Tenericutes, alternatively class Mollicutes in phylum Firmicutes (notable genus: Mycoplasma )
  27. Thermodesulfobacteria
  28. Thermotogae, deep branching
  29. Verrucomicrobia


Currently there are five phyla accepted by List of Prokaryotic names with Standing in Nomenclature (LPSN). [50]

  1. Crenarchaeota, second most common archaeal phylum
  2. Euryarchaeota, most common archaeal phylum
  3. Korarchaeota
  4. Nanoarchaeota, ultra-small symbiotes, single known species
  5. Thaumarchaeota

See also


    Related Research Articles

    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 the traditional kingdoms are not monophyletic, meaning that they do not consist of all the descendants of a common ancestor. The informal terms flora (plants), fauna (animals), and, in the 21st century, funga are also used.

    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 et al. in 1990 that divides cellular life forms into archaea, bacteria, and eukaryote domains. The key difference from earlier classifications is the splitting of archaea from bacteria.

    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. His research has led to discovery of a number of unicellular organisms (protists) and advocated for a variety of major taxonomic groups, such as the Chromista, Chromalveolata, Opisthokonta, Rhizaria, and Excavata. He was known for his systems of classification of all organisms.

    Mollicutes is a class of bacteria distinguished by the absence of a cell wall. The word "Mollicutes" is derived from the Latin mollis, and cutis. Individuals are very small, typically only 0.2–0.3 μm in size and have a very small genome size. They vary in form, although most have sterols that make the cell membrane somewhat more rigid. Many are able to move about through gliding, but members of the genus Spiroplasma are helical and move by twisting. The best-known genus in the Mollicutes is Mycoplasma.

    Archaeplastida Clade of eukaryotes containing land plants and some algae

    The Archaeplastida are a major group of eukaryotes, comprising the photoautotrophic red algae (Rhodophyta), green algae, land plants, and the minor group glaucophytes. It also includes the non-photosynthetic lineage Rhodelphidia, a predatorial (eukaryotrophic) flagellate that is sister to the Rhodophyta, and probably the microscopic picozoans. The Archaeplastida have chloroplasts that are surrounded by two membranes, suggesting that they were acquired directly through a single endosymbiosis event by feeding on a cyanobacterium. All other groups which have chloroplasts, besides the amoeboid genus Paulinella, have chloroplasts surrounded by three or four membranes, suggesting they were acquired secondarily from red or green algae. Unlike red and green algae, glaucophytes have never been involved in secondary endosymbiosis events.

    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 vertebrate body plan is one of many: invertebrates consist of many phyla.

    Corticata Type of plant

    Corticata, in the classification of eukaryotes, is a clade suggested by Thomas Cavalier-Smith to encompass the eukaryote supergroups of the following two groups:

    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).

    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.

    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 not animals, plants or 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 algae, invertebrates, or protozoans, the grouping is used for convenience. 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.

    Life form is an entity that is living, such as plants (flora) and animals (fauna). It is estimated that more than 99% of all species that ever existed on Earth, amounting to over five billion species, are extinct.

    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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