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Eukaryotic
Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bacteria and Archaea (both prokaryotes) make up the other two domains. The eukaryotes are usually now regarded as having emerged in the Archaea or as a sister of the Asgard archaea. This implies that there are only two domains of life, Bacteria and Archaea, with eukaryotes incorporated among archaea. Eukaryotes represent a small minority of the number of organisms, but, due to their generally much larger size, their collective global biomass is estimated to be about equal to that of prokaryotes. Eukaryotes emerged approximately 2.3–1.8 billion years ago, during the Proterozoic eon, likely as flagellated phagotrophs. Their name comes from the Greek εὖ (''eu'', "well" or "good") and κάρυον (''karyon'', "nut" or "kernel"). ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kingdom (biology)
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 (Animalia, Plantae, Fungi, Protista, Archaea/Archaebacteria, and Bacteria/Eubacteria) while textbooks in Great Britain, India, Greece, Brazil and other countries use five kingdoms only (Animalia, Plantae, Fungi, Protista and Monera). 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'' (for plants), ''fauna'' (for animals), and, in the 21st century, '' funga'' (for fungi) are also used for life present in a particular region or time. Definition and associated terms When Carl Linnaeus introduced the rank-based system of nomenclature into b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Archaeplastida
The Archaeplastida (or kingdom Plantae '' sensu lato'' "in a broad sense"; pronounced /ɑːrkɪ'plastɪdə/) 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. The cells of the Archaeplastida typically lack cen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Discoba
Excavata is a major supergroup of unicellular organisms belonging to the domain Eukaryota. It was first suggested by Simpson and Patterson in 1999 and introduced by Thomas Cavalier-Smith in 2002 as a formal taxon. It contains a variety of free-living and symbiotic forms, and also includes some important parasites of humans, including '' Giardia'' and '' Trichomonas''. Excavates were formerly considered to be included in the now obsolete Protista kingdom. They are classified based on their flagellar structures, and they are considered to be the most basal flagellate lineage. Phylogenomic analyses split the members of Excavata into three different and not all closely related groups: Discobids, Metamonads and Malawimonads. Except for Euglenozoa, they are all non-photosynthetic. Characteristics Most excavates are unicellular, heterotrophic flagellates. Only the Euglenozoa are photosynthetic. In some (particularly anaerobic intestinal parasites), the mitochondria have been grea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hemimastigophora
Hemimastigophora is a group of single-celled eukaryotic organisms with a single family, Spironemidae, first identified in 1988. Over the next 30 years, different authors proposed placing these organisms in various branches of the eukaryotes. In 2018 Lax ''et al''. reported the first genetic information for Spironemidae, and suggest that they are from an ancient lineage of eukaryotes which constitute a separate clade from all other eukaryotic kingdoms. It is potentially related to the Telonemia. History of classification Hemimastigophora was established in 1988 by Foissner ''et al''., as a new phylum with a single family, Spironemidae. Its placement on the eukaryote tree of life was unclear, but the authors suggested that the structure of its pellicle and cell nucleus indicated a close relationship with Euglenozoa. For 30 years after the description of the group, no genetic information was available. During that time, researchers proposed that it should be classified ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Opimoda
The Scotokaryotes (Cavalier-Smith) is a proposed basal Neokaryote clade as sister of the Diaphoretickes. Basal Scotokaryote groupings are the Metamonads, the Malawimonas and the Podiata. In this phylogeny the Discoba are sometimes seen as paraphyletic and basal Eukaryotes. An alternative to the Unikont– Bikont division was suggested by Derelle ''et al.'' in 2015, where they proposed the acronyms Opimoda–Diphoda respectively, as substitutes to the older terms. The name Opimoda is formed from the letters (shown in capitals) of OPIsthokonta and aMOebozoa. In this phylogeny Discoba belongs to the Diphoda clade. Taxonomy A proposed cladogram is See also *Diphoda A bikont ("two flagella") is any of the eukaryotic organisms classified in the group Bikonta. Many single-celled members of the group, and the presumed ancestor, have two flagella. Enzymes Another shared trait of bikonts is the fusion of two ... References {{Taxonbar, from=Q21399998 Eukaryote unran ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diphoda
A bikont ("two flagella") is any of the eukaryotic organisms classified in the group Bikonta. Many single-celled members of the group, and the presumed ancestor, have two flagella. Enzymes Another shared trait of bikonts is the fusion of two genes into a single unit: the genes for thymidylate synthase (TS) and dihydrofolate reductase (DHFR) encode a single protein with two functions. The genes are separately translated in unikonts. Relationships Some research suggests that a unikont (a eukaryotic cell with a single flagellum) was the ancestor of opisthokonts (Animals, Fungi, and related forms) and Amoebozoa, and a bikont was the ancestor of Archaeplastida (Plants and relatives), Excavata, Rhizaria, and Chromalveolata. Cavalier-Smith has suggested that Apusozoa, which are typically considered ''incertae sedis'', are in fact bikonts. Relationships within the bikonts are not yet clear. Cavalier-Smith has grouped the Excavata and Rhizaria into the Cabozoa and the Archaepl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lynn Margulis
Lynn Margulis (born Lynn Petra Alexander; March 5, 1938 – November 22, 2011) was an American evolutionary biologist, and was the primary modern proponent for the significance of symbiosis in evolution. Historian Jan Sapp has said that "Lynn Margulis's name is as synonymous with symbiosis as Charles Darwin's is with evolution." In particular, Margulis transformed and fundamentally framed current understanding of the evolution of cells with nuclei – an event Ernst Mayr called "perhaps the most important and dramatic event in the history of life" – by proposing it to have been the result of symbiotic mergers of bacteria. Margulis was also the co-developer of the Gaia hypothesis with the British chemist James Lovelock, proposing that the Earth functions as a single self-regulating system, and was the principal defender and promulgator of the five kingdom classification of Robert Whittaker. Throughout her career, Margulis' work could arouse intense objection (one grant applic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Supergroup (biology)
A supergroup, in evolutionary biology, is a large group of organisms that share one common ancestor and have important defining characteristics. It is an informal, mostly arbitrary rank in biological taxonomy that is often greater than phylum or kingdom, although some supergroups are also treated as phyla. Eukaryotic supergroups Since the decade of 2000's, the eukaryotic tree of life (abbreviated as eToL) has been divided into 5–8 major groupings called 'supergroups'. These groupings were established after the idea that only monophyletic groups should be accepted as ranks, as an alternative to the use of paraphyletic kingdom Protista. In the early days of the eToL six traditional supergroups were considered: Amoebozoa, Opisthokonta, "Excavata", Archaeplastida, "Chromalveolata" and Rhizaria. Since then, the eToL has been rearranged profoundly, and most of these groups were found as paraphyletic or lacked defining morphological characteristics that unite their members, whi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Halvaria
Halvaria is a grouping that includes Alveolata and Heterokonta (Stramenopiles). Analyses in 2007 and 2008 revealed that the Stramenopiles and the Alveolata are related, and form a reduced chromalveolate clade. They group together with the Rhizaria (originally one of the six major eukaryote groups) to form a clade dubbed the SAR supergroup. A phylogenomic analysis from 2016 cast doubt on Halvaria, suggesting that Alveolata is the sister group to Rhizaria (making the ''R + A clade'') through new rhizarian sequence data, and that support for Halvaria might be an artifact of low taxon sampling as well as long branch attraction. However, later analyses from 2021 support Halvaria as a solid clade. See also * Chromalveolata *Rhizaria The Rhizaria are an ill-defined but species-rich supergroup of mostly unicellular eukaryotes. Except for the Chlorarachniophytes and three species in the genus Paulinella in the phylum Cercozoa, they are all non-photosynthethic, but many forami ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ancyromonadida
Ancyromonadida or Planomonadida is a small group of biflagellated protists found in the soil and in aquatic habitats, where they feed on bacteria.Cavalier-Smith, T. (2013)Early evolution of eukaryote feeding modes, cell structural diversity, and classification of the protozoan phyla Loukozoa, Sulcozoa, and Choanozoa European journal of protistology, 49(2), 115-178. Includes freshwater or marine organisms, benthic, dorsoventrally compressed and with two unequal flagellae, each emerging from a separate pocket. The apical anterior flagellum can be very thin or end in the cell membrane, while the posterior flagellum is long and is inserted ventrally or laterally. The cell membrane is supported by a thin single layer teak and the mitochondrial crests are discoidal / flat. The group's placement is doubtful, as it seems to fall outside the five supergroups of eukaryotes. Cavalier-Smith considers that they constitute a basal group to Amoebozoa and Opisthokonta and places it together w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Provora
Provora is a proposed supergroup of eukaryotes made up of predatory microbes, "devouring voracious protists". It was reported that ten strains were isolated and cultured in 2022. They are predators of other microorganisms. Their discovery was very delayed, compared to other microorganisms in their environments, due to their rarity. Their 18S is very different from that of other eukaryotes, thus they were taxonomically placed in a separate supergroup. Phylogeny External relationships The supergroup Provora is composed of eukaryotic strains that form an ancient lineage within the clade Diaphoretickes. Phylogenetic analyses have recovered the following cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to ... shape: Internal relationships The phylogenetic relationships between ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diaphoretickes
Diaphoretickes () is a major group of eukaryotic organisms, with over 400,000 species. The majority of the earth's biomass that carries out photosynthesis belongs to Diaphoretickes. Diaphoretickes includes: * Archaeplastida (comprising red algae, glaucophytes, and green algae & land plants) * Cryptista * Haptista * Hemimastigophora * SAR supergroup (consisting of stramenopiles+alveolates+Rhizaria) * Telonemia Where Chromista is used as a taxon, its member groups all fall within Diaphoretickes. In 2012 Diaphoretickes received the following phylogenetic definition: :"The most inclusive clade containing ''Bigelowiella natans'' Moestrup & Sengco 2001 (Rhizaria), ''Tetrahymena thermophila'' Nanney & McCoy 1976 (Alveolata), ''Thalassiosira pseudonana'' Cleve 1873 (Stramenopiles), and ''Arabidopsis thaliana'' (Linnaeus) Heynhold, 1842 (Archaeplastida), but not ''Homo sapiens'' Linnaeus 1758 (Opisthokonta), ''Dictyostelium discoideum'' Raper 1935 (Amoebozoa) or ''Euglena gracilis'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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