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Archezoa Hypothesis
Archezoa was a kingdom proposed in the 20th century by Thomas Cavalier-Smith (1942–2021), and was believed to encompass eukaryotes which did not have mitochondria (and are therefore ''amitochondriate'') or peroxisomes (e.g. '' Giardia''). The category was dropped after it was discovered that all the amitochondriates were descendants of eukaryotes with mitochondria that had lost them. History Origin This taxonomic category was proposed upon the discovery that some protists lacked mitochondria, which suggested to Cavalier-Smith that the initial ancestor of eukaryotes emerged prior to the endosymbiosis of mitochondria (cf. '' Giardia''). Eukaryotes that eventually acquired a bacterial endosymbiont that became the mitochondria were placed in a taxonomic group which Cavalier-Smith called the Metakaryota, whereas the Archezoa represented a paraphyletic group involving four phyla representing primitive eukaryotes which evolved prior to the acquisition of mitochondria. Organisms makin ... [...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 int ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microsporidia
Microsporidia are a group of spore-forming unicellular parasites. These spores contain an extrusion apparatus that has a coiled polar tube ending in an anchoring disc at the apical part of the spore. They were once considered protozoans or protists, but are now known to be fungi, or a sister group to fungi. These fungal microbes are obligate eukaryotic parasites that use a unique mechanism to infect host cells. They have recently been discovered in a 2017 Cornell study to infect Coleoptera on a large scale. So far, about 1500 of the probably more than one million species are named. Microsporidia are restricted to animal hosts, and all major groups of animals host microsporidia. Most infect insects, but they are also responsible for common diseases of crustaceans and fish. The named species of microsporidia usually infect one host species or a group of closely related taxa. Approximately 10 percent of the species are parasites of vertebrates —several species, most of which ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biological Hypotheses
Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditary information encoded in genes, which can be transmitted to future generations. Another major theme is evolution, which explains the unity and diversity of life. Energy processing is also important to life as it allows organisms to move, grow, and reproduce. Finally, all organisms are able to regulate their own internal environments. Biologists are able to study life at multiple levels of organization, from the molecular biology of a cell to the anatomy and physiology of plants and animals, and evolution of populations.Based on definition from: Hence, there are multiple subdisciplines within biology, each defined by the nature of their research questions and the tools that they use. Like other scientists, biologists use the scientific meth ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Obsolete Eukaryote Taxa
Obsolescence is the state of being which occurs when an object, service, or practice is no longer maintained or required even though it may still be in good working order. It usually happens when something that is more efficient or less risky replaces it. The international standard IEC 62402:2019 Obsolescence Management defines obsolescence as the "transition from available to unavailable from the manufacturer in accordance with the original specification". Obsolete also refers to something that is already disused or discarded, or antiquated. Typically, obsolescence is preceded by a gradual decline in popularity. Consequences Driven by rapid technological changes, new components are developed and launched on the market with increasing speed. The result is a dramatic change in production methods of all components and their market availability. A growing industry sector is facing issues where life cycles of products no longer fit together with life cycles of required components ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Long Branch Attraction
In phylogenetics, long branch attraction (LBA) is a form of systematic error whereby distantly related lineages are incorrectly inferred to be closely related. LBA arises when the amount of molecular or morphological change accumulated within a lineage is sufficient to cause that lineage to appear similar (thus closely related) to another long-branched lineage, solely because they have both undergone a large amount of change, rather than because they are related by descent. Such bias is more common when the overall divergence of some taxa results in long branches within a phylogeny. Long branches are often attracted to the base of a phylogenetic tree, because the lineage included to represent an outgroup is often also long-branched. The frequency of true LBA is unclear and often debated, and some authors view it as untestable and therefore irrelevant to empirical phylogenetic inference. Although often viewed as a failing of parsimony-based methodology, LBA could in principle resul ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrogenosomes
A hydrogenosome is a membrane-enclosed organelle found in some anaerobic ciliates, flagellates, and fungi. Hydrogenosomes are highly variable organelles that have presumably evolved from protomitochondria to produce molecular hydrogen and ATP in anaerobic conditions. Hydrogenosomes were discovered in 1973 by D. G. Lindmark and M. Müller. Because hydrogenosomes hold evolutionary lineage significance for organisms living in anaerobic or oxygen-stressed environments, many research institutions have since documented their findings on how the organelle differs in various sources. History Hydrogenosomes were isolated, purified, biochemically characterized and named in the early 1970s by Lindmark and Müller at Rockefeller University. In addition to this seminal study on hydrogenosomes, they also demonstrated for the first time the presence of pyruvate:ferredoxin oxido-reductase and hydrogenase in eukaryotes. Further studies were subsequently conducted on the biochemical cytology ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mitosomes
A mitosome is an organelle found in some unicellular eukaryotic organisms, like in members of the supergroup Excavata. The mitosome was found and named in 1999, and its function has not yet been well characterized. It was termed a ''crypton'' by one group, but that name is no longer in use. The mitosome has been detected only in anaerobic or microaerophilic organisms that do not have mitochondria. These organisms do not have the capability of gaining energy from oxidative phosphorylation, which is normally performed by mitochondria. The mitosome was first described in ''Entamoeba histolytica,'' an intestinal parasite of humans. Mitosomes have also been identified in several species of Microsporidia and in '' Giardia intestinalis''. Origin and function Mitosomes are almost certainly derived from mitochondria. Like mitochondria, they have a double membrane and most proteins are delivered to them by a targeting sequence of amino acids. The targeting sequence is similar to that used ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parabasalid
The parabasalids are a group of flagellated protists within the supergroup Excavata. Most of these eukaryotic organisms form a symbiotic relationship in animals. These include a variety of forms found in the intestines of termites and cockroaches, many of which have symbiotic bacteria that help them digest cellulose in woody plants. Other species within this supergroup are known parasites, and include human pathogens. Characteristics The flagella are arranged in one or more clusters near the anterior of the cell. Their basal bodies are linked to parabasal fibers that attach to prominent Golgi complexes, distinctive to the group. Usually they also give rise to a sheet of cross-like microtubules that runs down the center of the cell and in some cases projects past the end. This is called the axostyle, but is different in structure from the axostyles of oxymonads. Parabasalids are anaerobic, and lack mitochondria, but this is now known to be a result of secondary loss, an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metamonad
The metamonads are microscopic eukaryotic organisms, a large group of flagellate amitochondriate Loukozoa. Their composition is not entirely settled, but they include the retortamonads, diplomonads, and possibly the parabasalids and oxymonads as well. These four groups are all anaerobic (many being aerotolerant anerobes), occurring mostly as 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 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 mitochondria secondarily, and retain both organelles and nuclear genes derived from them. Mitochondrial relics include h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protist
A protist () is any eukaryotic organism (that is, an organism whose cells contain a cell nucleus) that is not an animal, plant, or fungus. While it is likely that protists share a common ancestor (the last eukaryotic 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 the groups '' algae'', ''invertebrates'', and '' protozoans'', the biological category ''protist'' is used for convenience. Others classify any unicellular eukaryotic microorganism as a protist. The study of protists is termed protistology. History The classification of a third kingdom separate from animals and plants was first proposed by John Hogg in 1860 as the kingdom Protoctista; in 1866 Ernst Haeckel also proposed a third kingdom Protista as "the kingdom of primitive forms". Originally these also included prokaryotes ... [...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) and King's College London (PhD). 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-Smith was a guest inves ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microbiology And Molecular Biology Reviews
''Microbiology and Molecular Biology Reviews'' (published as MMBR) is a peer-reviewed scientific journal published by the American Society for Microbiology The American Society for Microbiology (ASM), originally the Society of American Bacteriologists, is a professional organization for scientists who study viruses, bacteria, fungi, algae, and protozoa as well as other aspects of microbiology. It wa .... History The journal was established in 1937 as ''Bacteriological Reviews'' () and changed its name in 1978 to ''Microbiological Reviews'' (). It obtained its current title in 1997. References External links * Delayed open access journals Microbiology journals Publications established in 1937 English-language journals Quarterly journals American Society for Microbiology academic journals {{microbiology-journal-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
