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Excavata
Excavata is an obsolete, extensive and diverse paraphyletic group of unicellular Eukaryota. The group was first suggested by Simpson and Patterson in 1999 and the name latinized and assigned a rank by Thomas Cavalier-Smith in 2002. It contains a variety of free-living and symbiotic protists, and includes some important parasites of humans such as ''Giardia'' and '' Trichomonas''. Excavates were formerly considered to be included in the now- obsolete Protista kingdom. They were distinguished from other lineages based on electron-microscopic information about how the cells are arranged (they have a distinctive ultrastructural identity). They are considered to be a basal flagellate lineage. On the basis of phylogenomic analyses, the group was shown to contain three widely separated eukaryote groups, the discobids, metamonads, and malawimonads. A current view of the composition of the excavates is given below, indicating that the group is paraphyletic. Except for some Eugleno ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Discobid
Excavata is an obsolete, extensive and diverse Paraphyly, paraphyletic group of unicellular Eukaryote, Eukaryota. The group was first suggested by Simpson and Patterson in 1999 and the name latinized and assigned a rank by Thomas Cavalier-Smith in 2002. It contains a variety of free-living and symbiotic protists, and includes some important parasites of humans such as ''Giardia'' and ''Trichomonas''. Excavates were formerly considered to be included in the now- obsolete Protist, Protista kingdom. They were distinguished from other lineages based on electron-microscopic information about how the cells are arranged (they have a distinctive ultrastructural identity). They are considered to be a Basal_(phylogenetics), basal flagellate lineage. On the basis of phylogenomic analyses, the group was shown to contain three widely separated eukaryote groups, the discobids, metamonads, and malawimonads. A current view of the composition of the excavates is given below, indicating that th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protist
A protist ( ) or protoctist is any eukaryotic organism that is not an animal, land plant, or fungus. Protists do not form a natural group, or clade, but are a paraphyletic grouping of all descendants of the last eukaryotic common ancestor excluding land plants, animals, and fungi. Protists were historically regarded as a separate taxonomic kingdom known as Protista or Protoctista. With the advent of phylogenetic analysis and electron microscopy studies, the use of Protista as a formal taxon was gradually abandoned. In modern classifications, protists are spread across several eukaryotic clades called supergroups, such as Archaeplastida ( photoautotrophs that includes land plants), SAR, Obazoa (which includes fungi and animals), Amoebozoa and " Excavata". Protists represent an extremely large genetic and ecological diversity in all environments, including extreme habitats. Their diversity, larger than for all other eukaryotes, has only been discovered in rece ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metamonad
The metamonads are a large group of flagellate amitochondriate microscopic eukaryotes. They include the retortamonads, diplomonads, parabasalids, oxymonads, and a range of more poorly studied taxa, most of which are free-living flagellates. All metamonads are anaerobic (many being aerotolerant anaerobes), and most members of the four groups listed above are symbiotes or parasites of animals, as is the case with ''Giardia lamblia'' which causes diarrhea in mammals. Characteristics A number of parabasalids and oxymonads are found in termite guts, and play an important role in breaking down the cellulose found in wood. Some other metamonads are parasites. These flagellates are unusual in lacking aerobic mitochondria. Originally they were considered among the most primitive eukaryotes, diverging from the others before mitochondria appeared. However, they are now known to have lost aerobic mitochondria secondarily, and retain both organelles and nuclear genes derived ultimate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Malawimonad
Malawimonads (order Malawimonadida) are a small group of microorganisms with a basal position in the evolutionary tree of eukaryotes, containing only three recognized species. They're considered part of a paraphyletic group known as "Excavata". Evolution It is clear that the malawimonads are a monophyletic clade at the base of Eukaryota, but there is no consensus on the specific relationships between other basal groups, such as Discoba, Metamonada, Ancyromonadida and Podiata. The sister group to Malawimonadida varies greatly between analyses. Some phylogenetic analyses find Malawimonadida as the sister group to Podiata. Other analyses recover Malawimonadida as the sister group of Discoba or Metamonada. Very few modern analyses recover the three clades, Malawimonadida, Discoba and Metamonada, as a monophyletic Excavata. Taxonomy History The malawimonads were first described as order Malawimonadida in 2003 by Thomas Cavalier-Smith. In 2013 they were also described as a class ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Flagellate
A flagellate is a cell or organism with one or more whip-like appendages called flagella. The word ''flagellate'' also describes a particular construction (or level of organization) characteristic of many prokaryotes and eukaryotes and their means of motion. The term presently does not imply any specific relationship or classification of the organisms that possess flagella. However, several derivations of the term "flagellate" (such as " dinoflagellate" and " choanoflagellate") are more formally characterized. Form and behavior Flagella in eukaryotes are supported by microtubules in a characteristic arrangement, with nine fused pairs surrounding two central singlets. These arise from a basal body. In some flagellates, flagella direct food into a cytostome or mouth, where food is ingested. Flagella role in classifying eukaryotes. Among protoctists and microscopic animals, a flagellate is an organism with one or more flagella. Some cells in other animals may be flage ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thomas Cavalier-Smith
Thomas (Tom) Cavalier-Smith, FRS, FRSC, NERC Professorial Fellow (21 October 1942 – 19 March 2021), 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. Life and career Cavalier-Smith was born on 21 October 1942 in London. His parents were Mary Maude (née Bratt) and Alan Hailes Spencer Cavalier Smith. He was educated at Norwich School, Gonville and Caius College, Cambridge (MA) in Biology and King's College London (PhD) in Zoology. He was under the supervision of Sir John Randall for his PhD thesis between 1964 and 1967; his thesis was entitled "''Organelle Development in'' Chlamydomonas reinhardii". From 1967 to 1969, Cavalier-S ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diaphoretickes
Diaphoretickes is a major group of eukaryote, eukaryotic organisms spanning over 400,000 species. The majority of the earth's biomass that carries out photosynthesis belongs to Diaphoretickes. In older classification systems, members of the Diaphoretickes were variously placed in the Kingdom (biology), kingdoms Protozoa or Protist, Protista. Etymology The name Diaphoretickes derives (''diaforetikés'') meaning diverse, dissimilar, referring to the wide morphology (biology), morphological and cellular diversity among members of this clade. History Eukaryotes, organisms whose cells contain a cell nucleus, nucleus, have been traditionally grouped into four kingdom (biology), kingdoms: animals, plants, fungi and protists. In the late 20th century, molecular phylogenetic analyses revealed that protists are a paraphyletic assortment of many independent evolutionary lineages or clades, from which animals, fungi and plants evolved. However, the relationships between these clades re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photosynthesis
Photosynthesis ( ) is a system of biological processes by which photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical energy necessary to fuel their metabolism. ''Photosynthesis'' usually refers to oxygenic photosynthesis, a process that produces oxygen. Photosynthetic organisms store the chemical energy so produced within intracellular organic compounds (compounds containing carbon) like sugars, glycogen, cellulose and starches. To use this stored chemical energy, an organism's cells metabolize the organic compounds through cellular respiration. Photosynthesis plays a critical role in producing and maintaining the oxygen content of the Earth's atmosphere, and it supplies most of the biological energy necessary for complex life on Earth. Some bacteria also perform anoxygenic photosynthesis, which uses bacteriochlorophyll to split hydrogen sulfide as a reductant instead of water, p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Euglenozoa
Euglenozoa are a large group of flagellate Discoba. They include a variety of common free-living species, as well as a few important parasites, some of which infect humans. Euglenozoa are represented by four major groups, ''i.e.,'' Kinetoplastea, Diplonemea, Euglenida, and Symbiontida. Euglenozoa are unicellular, mostly around in size, although some euglenids get up to long. Structure Most euglenozoa have two flagella, which are inserted parallel to one another in an apical or subapical pocket. In some these are associated with a cytostome or mouth, used to ingest bacteria or other small organisms. This is supported by one of three sets of microtubules that arise from the flagellar bases; the other two support the dorsal and ventral surfaces of the cell. Some other euglenozoa feed through absorption, and many euglenids possess chloroplasts, the only eukaryotes outside Diaphoretickes to do so without performing kleptoplasty, and so obtain energy through photosynthesis. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eukaryote
The eukaryotes ( ) constitute the Domain (biology), domain of Eukaryota or Eukarya, organisms whose Cell (biology), cells have a membrane-bound cell nucleus, nucleus. All animals, plants, Fungus, fungi, seaweeds, and many unicellular organisms are eukaryotes. They constitute a major group of Outline of life forms, life forms alongside the two groups of prokaryotes: the Bacteria and the Archaea. Eukaryotes represent a small minority of the number of organisms, but given their generally much larger size, their collective global biomass is much larger than that of prokaryotes. The eukaryotes emerged within the archaeal Kingdom (biology), kingdom Asgard (Archaea), Promethearchaeati and its sole phylum Promethearchaeota. This implies that there are only Two-domain system, two domains of life, Bacteria and Archaea, with eukaryotes incorporated among the Archaea. Eukaryotes first emerged during the Paleoproterozoic, likely as Flagellated cell, flagellated cells. The leading evolutiona ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trichomonas
''Trichomonas'' is a genus of anaerobic excavate parasites of vertebrates. It was first discovered by Alfred François Donné in 1836 when he found these parasites in the vagina of a patient suffering from vaginitis, an inflammation of the vagina. Donné named the genus from its morphological characteristics. The prefix tricho- originates from the Ancient Greek word (thrix) meaning hair, describing ''Trichomonas''’s flagella. The suffix -monas ( – single unit), describes its similarity to unicellular organisms from the genus ''Monas''. Habitat and ecology ''Trichomonas'' is typically found in anaerobic environments. It is a known parasite of many different animals including humans, birds, dogs, and cats. In humans, it can be found in the urogenital tract and in the oral cavity. It is estimated that 276 million new cases of urogenital infections occur each year. Depending on the ''Trichomonas'' species, it can either be transmitted through direct sexual contact or through ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
