Bikonta
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Bikonta
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 Archaeplastid ...
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Opisthokonts
The opisthokonts () are a broad group of eukaryotes, including both the animal and fungus kingdoms. The opisthokonts, previously called the "Fungi/Metazoa group", are generally recognized as a clade. Opisthokonts together with Apusomonadida and Breviata comprise the larger clade Obazoa. Flagella and other characteristics A common characteristic of opisthokonts is that flagellate cells, such as the sperm of most animals and the spores of the chytrid fungi, propel themselves with a single ''posterior'' flagellum. It is this feature that gives the group its name. In contrast, flagellate cells in other eukaryote groups propel themselves with one or more ''anterior'' flagella. However, in some opisthokont groups, including most of the fungi, flagellate cells have been lost. Opisthokont characteristics include synthesis of extracellular chitin in exoskeleton, cyst/spore wall, or cell wall of filamentous growth and hyphae; the extracellular digestion of substrates with osmotrophic a ...
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Corticata
Corticata ("one with a cortex"), in the classification of eukaryotes (living organisms with a cell nucleus), is a clade suggested by Thomas Cavalier-Smith to encompass the eukaryote supergroups of the following two groups: * Plantae, or Archaeplastida (plants, red algae, green algae, and glaucophytes) * Chromalveolata (a group including kelp, water moulds, ciliates, dinoflagellates, and other organisms) Cavalier-Smith currently includes Rhizaria as well, resulting in an equivalency to Diaphoretickes. See also *Bikont 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 ge ... * Cabozoa References Bikont unranked clades Diaphoretickes {{Bikont-stub ...
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Mesoproterozoic
The Mesoproterozoic Era is a geologic era that occurred from . The Mesoproterozoic was the first era of Earth's history for which a fairly definitive geological record survives. Continents existed during the preceding era (the Paleoproterozoic), but little is known about them. The continental masses of the Mesoproterozoic were more or less the same ones that exist today, although their arrangement on the Earth's surface was different. Major events and characteristics The major events of this era are the breakup of the Columbia supercontinent, the formation of the Rodinia supercontinent, and the evolution of sexual reproduction. This era is marked by the further development of continental plates and plate tectonics. The supercontinent of Columbia broke up between 1500 and 1350 million years ago, and the fragments reassembled into the supercontinent of Rodinia around 1100 to 900 million years ago, on the time boundary between the Mesoproterozoic and the subsequent Neoproterozoi ...
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Chromalveolate
Chromalveolata was a eukaryote supergroup present in a major classification of 2005, then regarded as one of the six major groups within the eukaryotes. It was a refinement of the kingdom Chromista, first proposed by Thomas Cavalier-Smith in 1981. Chromalveolata was proposed to represent the organisms descended from a single secondary endosymbiosis involving a red alga and a bikont. The plastids in these organisms are those that contain chlorophyll c. However, the monophyly of the Chromalveolata has been rejected. Thus, two papers published in 2008 have phylogenetic trees in which the chromalveolates are split up, and recent studies continue to support this view. Groups and classification Historically, many chromalveolates were considered plants, because of their cell walls, photosynthetic ability, and in some cases their morphological resemblance to the land plants (Embryophyta). However, when the five-kingdom system (proposed in 1969) took prevalence over the animal ...
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Plants+HC+SAR Megagroup
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'' K ...
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Eukaryote
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"). Euka ...
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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'' K ...
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