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33-515: Nanoarchaeota (Greek, "dwarf or tiny ancient one") is a proposed phylum ( Candidatus Nanoarchaeota) in the domain Archaea that currently has only one representative, Nanoarchaeum equitans , which was discovered in a submarine hydrothermal vent and first described in 2002. Members of the Nanoarchaeota are associated with different host organisms and environmental conditions. Despite small size,

66-439: A terminal electron acceptor often refers to either the last compound to receive an electron in an electron transport chain , such as oxygen during cellular respiration , or the last cofactor to receive an electron within the electron transfer domain of a reaction center during photosynthesis . All organisms obtain energy by transferring electrons from an electron donor to an electron acceptor. One practical illustration of

99-447: 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

132-405: A diameter of approximately 400 nm , and have a very short and compact DNA sequence with the entire genome containing only 490,885 base pairs . While they have the genetic code to carry out processing and repair, they cannot carry out certain biosynthetic and metabolic processes such as lipid, amino-acid, cofactor , or nucleotide synthesis. Due to its limited machinery, it is an obligate parasite,

165-477: 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. 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

198-422: 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

231-689: A phylum, other phylum-level ranks appear, such as the case of Bacillariophyta (diatoms) within Ochrophyta . These differences became irrelevant after the adoption of a cladistic approach by the ISP, where taxonomic ranks are excluded from the classifications after being considered superfluous and unstable. Many authors prefer this usage, which lead to the Chromista-Protozoa scheme becoming obsolete. Currently there are 40 bacterial phyla (not including " Cyanobacteria ") that have been validly published according to

264-486: A reduced genome and limited respiration, members of the Nanoarchaeota have unusual metabolic features. For example, N. equitans has a complex and highly developed intercellular communication system. The phylogeny of the Nanoarchaeota is anchored by its only cultured representative, Nanoarchaeum equitans , which clusters in a separate evolutionary group than other archaea, which have recently been reclassified. Further analysis has shown that N. equitans diverged early on in

297-467: Is a paraphyletic taxon, 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 . Protist taxonomy has long been unstable, with different approaches and definitions resulting in many competing classification schemes. Many of the phyla listed below are used by

330-457: Is compatible with a host dependent lifestyle. Certain nanaoarchaeotes still have genes for the CRISPR-Cas systems, archaeal flagella , and the gluconeogenesis pathway. Nanoarchaeotes are obligate symbionts that grow attached to an archaeal host known as Ignicoccus . Both terrestrial hot springs and underwater hydrothermal vents have yielded isolates in the genus Nanoarchaeum . However, there

363-469: Is evidence that nanoarcheotes reside in a variety of habitats outside of marine thermal vents.  Genetic evidence for members of the Nanoarchaeota has been discovered to be pervasive in terrestrial hot springs and mesophilic hypersaline habitats using primers created based on the sequence of the 16S rRNA gene of Nanoarchaeum equitans . In addition, the discovery of ribosomal sequences in photic-zone water samples taken distant from hydrothermal vents raises

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396-472: Is generally included in kingdom Fungi, though its exact relations remain uncertain, and it is considered a protozoan by the International Society of Protistologists (see Protista , below). Molecular analysis of Zygomycota has found it to be polyphyletic (its members do not share an immediate ancestor), which is considered undesirable by many biologists. Accordingly, there is a proposal to abolish

429-459: Is that all organisms in a phylum should be clearly more closely related to one another than to any other group. 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,

462-558: The Bacteriological Code Currently there are 2 phyla that have been validly published according to the Bacteriological Code Other phyla that have been proposed, but not validly named, include: Electron acceptor The electron accepting power of an electron acceptor is measured by its redox potential . In the simplest case, electron acceptors are reduced by one electron. The process can alter

495-552: The Catalogue of Life , and correspond to the Protozoa-Chromista scheme, with updates from the latest (2022) publication by Cavalier-Smith . Other phyla are used commonly by other authors, and are adapted from the system used by the International Society of Protistologists (ISP). Some of the descriptions are based on the 2019 revision of eukaryotes by the ISP. The number of protist phyla varies greatly from one classification to

528-459: 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 ). On the other hand, the highly parasitic phylum Mesozoa was divided into two phyla ( Orthonectida and Rhombozoa ) when it was discovered

561-495: The Greek phylon ( φῦλον , "race, stock"), related to phyle ( φυλή , "tribe, clan"). 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"): "perhaps such a real and completely self-contained unity is the aggregate of all species which have gradually evolved from one and

594-510: The Orthonectida are probably 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 placing taxa in clades without any formal ranking of group size. A definition of a phylum based on body plan has been proposed by paleontologists Graham Budd and Sören Jensen (as Haeckel had done

627-491: 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 . 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. Protista

660-525: The creation of monomers like amino acids, nucleotides, and coenzymes , lack recognizable genes in this organism. Phylum (biology) In biology , a phylum ( / ˈ f aɪ l əm / ; pl. : 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

693-980: The evolution of Archaea, as indicated by the 16S rRNA sequence. This suggests that they occupy a deeply branching position within this group. The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN) and the National Center for Biotechnology Information (NCBI). " Ca. Tiddalikarchaeum anstoanum " " Ca. Jingweiarchaeum tengchongense " " Ca. Haiyanarchaeum thermophilum " " Ca. Rehaiarchaeum fermentans " " Ca. Acidifodinimicrobium mancum " " Ca. P. paracidiphilum" " Ca. P. paracidiphilum" " Ca. P. tengchongense" "Pacearchaeales" "Woesearchaeales" " Nanoarchaeum equitans " " Ca. Nanoclepta minuta " Nanobdella aerobiophila " Ca. N. acidilobi" " Ca. N. stetteri" Cells of N. equitans are spherical with

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726-504: 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 . Wolf plants Hepatophyta Liver plants Coniferophyta Cone-bearing plant Phylum Microsporidia

759-468: The four embranchements of Georges Cuvier . Informally, phyla can be thought of as groupings of organisms based on general specialization of body plan . 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). Attempting to define

792-536: The idea that each of the phyla represents a distinct body plan. 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. Total numbers are estimates; figures from different authors vary wildly, not least because some are based on described species, 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

825-703: The influential (though contentious) Cavalier-Smith system in equating "Plantae" with Archaeplastida , 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, 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), or for conifers alone as below. Since

858-411: The next. The Catalogue of Life includes Rhodophyta and Glaucophyta in kingdom Plantae, but other systems consider these phyla part of Protista. In addition, less popular classification schemes unite Ochrophyta and Pseudofungi under one phylum, Gyrista , and all alveolates except ciliates in one phylum Myzozoa , later lowered in rank and included in a paraphyletic phylum Miozoa . Even within

891-528: The only one known in the Archaea. Because of their unusual ss rRNA sequences, they are difficult to detect using standard polymerase chain reaction methods. Cells of N. equitans contain a normal S-layer with sixfold symmetry with a 15 nm lattice constant. Small cells between 100 and 400 nm in diameter and highly streamlined genomes of 0.491-0.606 Mbp characterize nanoarchaeotes. The genomes of described nanoarchaeotes demonstrate different degrees of reduction, which

924-436: 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

957-420: The possibility that Nanoarchaeota are an ubiquitous and diversified group of Archaea that can live in habitats with a variety of temperatures and geochemical settings. Although much of the metabolism of members of the Nanoarchaeota is unknown, its host is an autotroph that grows on elemental sulphur as an electron acceptor and H 2 as an electron donor . The majority of recognized metabolic processes, such as

990-411: The same common original form, as, for example, all vertebrates. We name this aggregate [a] Stamm [i.e., stock] ( 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. The definitions of zoological phyla have changed from their origins in the six Linnaean classes and

1023-438: The structure of the acceptor substantially. When the added electron is highly delocalized, the structural consequences of the reduction can be subtle. The central C-C distance in the electron acceptor tetracyanoethylene elongates from 135 to 143 pm upon acceptance of an electron. In the formation of some donor-acceptor complexes, less than one electron is transferred. TTF-TCNQ is an charge transfer complex . In biology ,

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1056-416: The terms as equivalent. 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 among phyla within larger clades like Ecdysozoa and Embryophyta . The term phylum was coined in 1866 by Ernst Haeckel from

1089-420: The total number of nematode species include 10,000–20,000; 500,000; 10 million; and 100 million. 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

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