1.
Nuclearia
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Nucleariida is a group of amoebae with filose pseudopods, known mostly from soils and freshwater. They are distinguished from the superficially similar vampyrellids mainly by having mitochondria with discoid cristae, nucleariids are opisthokonts, the group which includes animals, fungi and several smaller groups. Several studies place the nucleariids as a group to the fungi. The genera Rabdiophrys, Pinaciophora, and Pompholyxophrys, freshwater forms with hollow siliceous scales or spines, were included in Nucleariida. In the past, nucleariids were included among the heliozoa as the Rotosphaerida, according to a 2009 paper, Fonticula, a cellular slime mold, is an opisthokont and more closely related to Nuclearia than to fungi
2.
Taxonomy (biology)
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Taxonomy is the science of defining groups of biological organisms on the basis of shared characteristics and giving names to those groups. The exact definition of taxonomy varies from source to source, but the core of the remains, the conception, naming. There is some disagreement as to whether biological nomenclature is considered a part of taxonomy, the broadest meaning of taxonomy is used here. The word taxonomy was introduced in 1813 by Candolle, in his Théorie élémentaire de la botanique, the term alpha taxonomy is primarily used today to refer to the discipline of finding, describing, and naming taxa, particularly species. In earlier literature, the term had a different meaning, referring to morphological taxonomy, ideals can, it may be said, never be completely realized. They have, however, a value of acting as permanent stimulants. Some of us please ourselves by thinking we are now groping in a beta taxonomy, turrill thus explicitly excludes from alpha taxonomy various areas of study that he includes within taxonomy as a whole, such as ecology, physiology, genetics, and cytology. He further excludes phylogenetic reconstruction from alpha taxonomy, thus, Ernst Mayr in 1968 defined beta taxonomy as the classification of ranks higher than species. This activity is what the term denotes, it is also referred to as beta taxonomy. How species should be defined in a group of organisms gives rise to practical and theoretical problems that are referred to as the species problem. The scientific work of deciding how to define species has been called microtaxonomy, by extension, macrotaxonomy is the study of groups at higher taxonomic ranks, from subgenus and above only, than species. While some descriptions of taxonomic history attempt to date taxonomy to ancient civilizations, earlier works were primarily descriptive, and focused on plants that were useful in agriculture or medicine. There are a number of stages in scientific thinking. Early taxonomy was based on criteria, the so-called artificial systems. Later came systems based on a complete consideration of the characteristics of taxa, referred to as natural systems, such as those of de Jussieu, de Candolle and Bentham. The publication of Charles Darwins Origin of Species led to new ways of thinking about classification based on evolutionary relationships and this was the concept of phyletic systems, from 1883 onwards. This approach was typified by those of Eichler and Engler, the advent of molecular genetics and statistical methodology allowed the creation of the modern era of phylogenetic systems based on cladistics, rather than morphology alone. Taxonomy has been called the worlds oldest profession, and naming and classifying our surroundings has likely been taking place as long as mankind has been able to communicate
3.
Eukaryote
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A eukaryote is any organism whose cells contain a nucleus and other organelles enclosed within membranes. Eukaryotes belong to the taxon Eukarya or Eukaryota, the presence of a nucleus gives eukaryotes their name, which comes from the Greek εὖ and κάρυον. Eukaryotic cells also contain other membrane-bound organelles such as mitochondria and the Golgi apparatus, in addition, plants and algae contain chloroplasts. Eukaryotic organisms may be unicellular or multicellular, only eukaryotes form multicellular organisms consisting of many kinds of tissue made up of different cell types. Eukaryotes can reproduce asexually through mitosis and sexually through meiosis and gamete fusion. In mitosis, one cell divides to produce two identical cells. In meiosis, DNA replication is followed by two rounds of division to produce four daughter cells each with half the number of chromosomes as the original parent cell. These act as sex cells resulting from genetic recombination during meiosis, the domain Eukaryota appears to be monophyletic, and so makes up one of the three domains of life. The two other domains, Bacteria and Archaea, are prokaryotes and have none of the above features, eukaryotes represent a tiny minority of all living things. However, due to their larger size, eukaryotes collective worldwide biomass is estimated at about equal to that of prokaryotes. Eukaryotes first developed approximately 1. 6–2.1 billion years ago, in 1905 and 1910, the Russian biologist Konstantin Mereschkowsky argued three things about the origin of nucleated cells. Firstly, plastids were reduced cyanobacteria in a symbiosis with a non-photosynthetic host, secondly, the host had earlier in evolution formed by symbiosis between an amoeba-like host and a bacteria-like cell that formed the nucleus. Thirdly, plants inherited photosynthesis from cyanobacteria, the split between the prokaryotes and eukaryotes was introduced in the 1960s. The concept of the eukaryote has been attributed to the French biologist Edouard Chatton, the terms prokaryote and eukaryote were more definitively reintroduced by the Canadian microbiologist Roger Stanier and the Dutch-American microbiologist C. B. van Niel in 1962. In his 1938 work Titres et Travaux Scientifiques, Chatton had proposed the two terms, calling the bacteria prokaryotes and organisms with nuclei in their cells eukaryotes. However he mentioned this in one paragraph, and the idea was effectively ignored until Chattons statement was rediscovered by Stanier. In 1967, Lynn Margulis provided microbiological evidence for endosymbiosis as the origin of chloroplasts and mitochondria in cells in her paper. In the 1970s, Carl Woese explored microbial phylogenetics, studying variations in 16S ribosomal RNA and this helped to uncover the origin of the eukaryotes and the symbiogenesis of two important eukaryote organelles, mitochondria and chloroplasts
4.
Unikont
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The taxonomic affinities of the members of this clade were originally described and proposed by Thomas Cavalier-Smith. It includes amoebozoa, opisthokonts, and possibly Apusozoa, the validity of this proposed taxonomy has yet to ruled upon by the Society of Protistologists. Further work by Cavalier-Smith has shown that Sulcozoa is paraphyletic, Apusozoa also appears to be paraphyetic. Varisulca has been redefined to include planomonads, Mantamonas and Collodictyon, a new taxon has been created - Glissodiscea - for the planomonads and Mantamonas. Again, the validity of this revised taxonomy awaits approval by the Society, Amoebozoa seems to be monophyletic with two major branches, Conosa and Lobosa. Conosa is divided into the aerobic infraphylum Semiconosia and secondarily anaerobic Archamoebae, Lobosa consists entirely of non-flagellated lobose amoebae and has been divided into two classes, Discosea, which have flattened cells, and Tubulinea, which has predominantly tube-shaped pseudopodia. The group includes eukaryotic cells that, for the most part, have a single emergent flagellum, the unikonts include opisthokonts and Amoebozoa. By contrast, other eukaryotic groups, which more often have two emergent flagella, are often referred to as bikonts. Bikonts include Archaeplastida, Excavata, Rhizaria, and Chromalveolata, the unikonts have a triple-gene fusion that is lacking in the bikonts. This must have involved a double fusion, a pair of events, supporting the shared ancestry of Opisthokonta. Cavalier-Smith originally proposed that unikonts ancestrally had a single flagellum and single basal body and this is unlikely, however, as flagellated opisthokonts, as well as some flagellated Amoebozoa, including Breviata, actually have two basal bodies, as in typical bikonts. This paired arrangement can also be seen in the organization of centrioles in animal cells. In spite of the name of the group, the ancestor of all unikonts was probably a cell with two basal bodies
5.
Opisthokont
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The opisthokonts, sometimes referred to as the Fungi/Metazoa group, are generally recognized as a monophyletic clade. One common characteristic of opisthokonts is that flagellate cells, such as the sperm of most animals and 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, in some opisthokont groups, including most of the fungi, flagellate cells have been lost. The close relationship between animals and fungi was suggested by Thomas Cavalier-Smith in 1987, who used the informal name opisthokonta, early phylogenies placed fungi near the plants and other groups that have mitochondria with flat cristae, but this character varies. Animals and fungi are more closely related to amoebas than they are to plants. Opisthokonts are divided into Holomycota or Nucletmycea and Holozoa, no opisthokonts basal to the Holomycota/Holozoa split have yet been identified, however, a 2013 study suggests that there may be many more unicellular opisthokonts than previously suspected. Holomycota and Holozoa are composed of the following groups, the choanoflagellates have a circular mitochondrial DNA genome with long intergenic regions. This is four times as large as animal mitochondrial genomes and contains twice as many protein genes, the ichthyosporeans have a two amino acid deletion in their elongation factor 1 α gene that is considered characteristic of fungi. The ichthyosl genome is >200 kilobase pairs in length and consists of several hundred linear chromosomes that share elaborate terminal-specific sequence patterns
6.
Fungus
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A fungus is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from the other eukaryotic life kingdoms of plants, a characteristic that places fungi in a different kingdom from plants, bacteria and some protists, is chitin in their cell walls. Similar to animals, fungi are heterotrophs, they acquire their food by absorbing dissolved molecules, growth is their means of mobility, except for spores, which may travel through the air or water. Fungi are the principal decomposers in ecological systems and this fungal group is distinct from the structurally similar myxomycetes and oomycetes. The discipline of biology devoted to the study of fungi is known as mycology, in the past, mycology was regarded as a branch of botany, although it is now known fungi are genetically more closely related to animals than to plants. Abundant worldwide, most fungi are inconspicuous because of the size of their structures. Fungi include symbionts of plants, animals, or other fungi and they may become noticeable when fruiting, either as mushrooms or as molds. Fungi perform a role in the decomposition of organic matter and have fundamental roles in nutrient cycling. Since the 1940s, fungi have been used for the production of antibiotics, Fungi are also used as biological pesticides to control weeds, plant diseases and insect pests. Many species produce bioactive compounds called mycotoxins, such as alkaloids and polyketides, the fruiting structures of a few species contain psychotropic compounds and are consumed recreationally or in traditional spiritual ceremonies. Fungi can break down manufactured materials and buildings, and become significant pathogens of humans, losses of crops due to fungal diseases or food spoilage can have a large impact on human food supplies and local economies. The fungus kingdom encompasses a diversity of taxa with varied ecologies, life cycle strategies. However, little is known of the biodiversity of Kingdom Fungi. Advances in molecular genetics have opened the way for DNA analysis to be incorporated into taxonomy, phylogenetic studies published in the last decade have helped reshape the classification within Kingdom Fungi, which is divided into one subkingdom, seven phyla, and ten subphyla. The English word fungus is directly adopted from the Latin fungus, used in the writings of Horace, a group of all the fungi present in a particular area or geographic region is known as mycobiota, e. g. the mycobiota of Ireland. Like plants, fungi grow in soil and, in the case of mushrooms, form conspicuous fruit bodies. The fungi are now considered a kingdom, distinct from both plants and animals, from which they appear to have diverged around one billion years ago. Fungi have membrane-bound cytoplasmic organelles such as mitochondria, sterol-containing membranes and they have a characteristic range of soluble carbohydrates and storage compounds, including sugar alcohols, disaccharides, and polysaccharides
7.
Microsporidia
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The Microsporidia constitute a group of spore-forming unicellular parasites. They were once considered protozoans or protists, but are now known to be fungi, loosely 1500 of the probably more than one million species are named now. Microsporidia are restricted to hosts, and all major groups of animals host microsporidia. Most infect insects, but they are responsible for common diseases of crustaceans. The named species of microsporidia usually infect one host species or a group of related taxa. Several species, most of which are opportunistic, also infect humans, approximately 10 percent of the species are parasites of vertebrates—including humans, in which they can cause microsporidiosis. After infection they influence their hosts in various ways and all organs and tissues are invaded, some species are lethal, and a few are used in biological control of insect pests. Parasitic castration, gigantism, or change of host sex are all potential effects of microsporidian parasitism, in the most advanced cases of parasitism the microsporidium rules the host cell completely and controls its metabolism and reproduction, forming a xenoma. Replication takes place within the cells, which are infected by means of unicellular spores. These vary from 1–40 μm, making some of the smallest eukaryotes. Microsporidia that infect mammals are 1. 0–4.0 μm and they also have the smallest eukaryotic genomes. The terms microsporidium and microsporidian are used as names for members of the group. The name Microsporidium Balbiani,1884 is also used as a genus for incertae sedis members. Microsporidia lack mitochondria, instead possessing mitosomes and they also lack motile structures, such as flagella. Microsporidia produce highly resistant spores, capable of surviving outside their host for up to several years, spore morphology is useful in distinguishing between different species. Spores of most species are oval or pyriform, but rod-shaped or spherical spores are not unusual, a few genera produce spores of unique shape for the genus. The anterior half of the spore contains a harpoon-like apparatus with a long, thread-like polar filament, the anterior part of the polar filament is surrounded by a polaroplast, a lamella of membranes. Behind the polar filament, there is a posterior vacuole, in the gut of the host the spore germinates, it builds up osmotic pressure until its rigid wall ruptures at its thinnest point at the apex
8.
Synonym (taxonomy)
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For example, Linnaeus was the first to give a scientific name to the Norway spruce, which he called Pinus abies. This name is no longer in use, it is now a synonym of the current scientific name which is Picea abies, unlike synonyms in other contexts, in taxonomy a synonym is not interchangeable with the name of which it is a synonym. In taxonomy, synonyms are not equals, but have a different status, for any taxon with a particular circumscription, position, and rank, only one scientific name is considered to be the correct one at any given time. A synonym cannot exist in isolation, it is always an alternative to a different scientific name, given that the correct name of a taxon depends on the taxonomic viewpoint used a name that is one taxonomists synonym may be another taxonomists correct name. Synonyms may arise whenever the same taxon is described and named more than once, independently. They may also arise when existing taxa are changed, as when two taxa are joined to one, a species is moved to a different genus. To the general user of scientific names, in such as agriculture, horticulture, ecology, general science. A synonym is a name that was used as the correct scientific name but which has been displaced by another scientific name. Thus Oxford Dictionaries Online defines the term as a name which has the same application as another. In handbooks and general texts, it is useful to have mentioned as such after the current scientific name. Synonyms used in this way may not always meet the strict definitions of the synonym in the formal rules of nomenclature which govern scientific names. Changes of scientific name have two causes, they may be taxonomic or nomenclatural, a name change may be caused by changes in the circumscription, position or rank of a taxon, representing a change in taxonomic, scientific insight. A name change may be due to purely nomenclatural reasons, that is, based on the rules of nomenclature, the earliest such name is called the senior synonym, while the later name is the junior synonym. One basic principle of zoological nomenclature is that the earliest correctly published name, synonyms are important because if the earliest name cannot be used, then the next available junior synonym must be used for the taxon. Objective synonyms refer to taxa with the type and same rank. For example, John Edward Gray published the name Antilocapra anteflexa in 1855 for a species of pronghorn, however, it is now commonly accepted that his specimen was an unusual individual of the species Antilocapra americana published by George Ord in 1815. Ords name thus takes precedence, with Antilocapra anteflexa being a subjective synonym. Objective synonyms are common at the level of genera, because for various reasons two genera may contain the type species, these are objective synonyms
9.
Protist
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Protist is an informal term for any eukaryotic organism that is not an animal, plant or fungus. The protists do not form a group, or clade. Besides their relatively simple levels of organization, protists do not necessarily have much in common, others use the term protist more broadly, to encompass both microbial eukaryotes and macroscopic organisms that do not fit into the other traditional kingdoms. In cladistic systems, there are no equivalents to the taxa Protista or Protoctista, in cladistic classification, the contents of Protista are distributed among various supergroups and Protista, Protoctista and Protozoa are considered obsolete. However, the term protist continues to be used informally as a term for eukaryotic microorganisms. For example, the phrase protist pathogen may be used to denote any disease-causing microbe which is not bacteria, virus, the term protista was first used by Ernst Haeckel in 1866. Some protists, sometimes called ambiregnal protists, have considered to be both protozoa and algae or fungi, and names for these have been published under either or both of the ICN and the ICZN. Conflicts, such as these – for example the dual-classification of Euglenids and Dinobryons and these traditional subdivisions, largely based on superficial commonalities, have been replaced by classifications based on phylogenetics. Molecular analyses in modern taxonomy have been used to redistribute former members of this group into diverse, however, the older terms are still used as informal names to describe the morphology and ecology of various protists. For example, the term protozoa is used to refer to species of protists that do not form filaments. Among the pioneers in the study of the protists, which were almost ignored by Linnaeus except for some genera were Leeuwenhoek, O. F. Müller, C. G. Ehrenberg, the first groups used to classify microscopic organism were the Animalcules and the Infusoria. In 1817, the German naturalist Georg August Goldfuss introduced the word Protozoa to refer to such as ciliates. After the cell theory of Schwann and Schleiden, this group was modified in 1848 by Carl von Siebold to include only animal-like unicellular organisms, such as foraminifera and amoebae. He defined the Protoctista as a kingdom of nature, in addition to the then-traditional kingdoms of plants. The kingdom of minerals was later removed from taxonomy in 1866 by Ernst Haeckel, leaving plants, animals, in 1938, Herbert Copeland resurrected Hoggs label, arguing that Haeckels term Protista included anucleated microbes such as bacteria, which the term Protoctista did not. In contrast, Copelands term included nucleated eukaryotes such as diatoms, green algae and this classification was the basis for Whittakers later definition of Fungi, Animalia, Plantae and Protista as the four kingdoms of life. The kingdom Protista was later modified to separate prokaryotes into the kingdom of Monera. Many systematists today do not treat Protista as a formal taxon, some systematists judge paraphyletic taxa acceptable, and use Protista in this sense as a formal taxon
10.
Nucleariida
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Nucleariida is a group of amoebae with filose pseudopods, known mostly from soils and freshwater. They are distinguished from the superficially similar vampyrellids mainly by having mitochondria with discoid cristae, nucleariids are opisthokonts, the group which includes animals, fungi and several smaller groups. Several studies place the nucleariids as a group to the fungi. The genera Rabdiophrys, Pinaciophora, and Pompholyxophrys, freshwater forms with hollow siliceous scales or spines, were included in Nucleariida. In the past, nucleariids were included among the heliozoa as the Rotosphaerida, according to a 2009 paper, Fonticula, a cellular slime mold, is an opisthokont and more closely related to Nuclearia than to fungi
11.
Holozoa
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Holozoa is a group of organisms that includes animals and their closest single-celled relatives, but excludes fungi. Holozoa is also an old name for the tunicate genus Distaplia, proterospongia is an example of a colonial choanoflagellate that may shed light on the origin of sponges. The affinities of the other single-celled holozoans only began to be recognized in the 1990s, a group of mostly parasitic species called Icthyosporea or Mesomycetozoea is sometimes grouped with other species in Mesomycetozoa. The amoeboid genera Ministeria and Capsaspora may be united in a group called Filasterea by the structure of their thread-like pseudopods, along with choanoflagellates, filastereans may be closely related to animals, and one analysis grouped them together as the clade Filozoa. The oldest fossils of holozoans are animals, which date back to the Ediacaran period, the most up to date cladogram is
12.
Parasitism
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In biology/ecology, parasitism is a non-mutual relationship between species, where one species, the parasite, benefits at the expense of the other, the host. Traditionally parasite referred primarily to organisms visible to the naked eye, Parasites can be microparasites, which are typically smaller, such as protozoa, viruses, and bacteria. Examples of parasites include the plants mistletoe and cuscuta, and animals such as hookworms, unlike predators, parasites typically do not kill their host, are generally much smaller than their host, and will often live in or on their host for an extended period. Both are special cases of consumer-resource interactions, Parasites show a high degree of specialization, and reproduce at a faster rate than their hosts. Classic examples of parasitism include interactions between vertebrate hosts and tapeworms, flukes, the Plasmodium species, and fleas, parasitism differs from the parasitoid relationship in that parasitoids generally kill their hosts. Parasites reduce host biological fitness by general or specialized pathology, such as parasitic castration and impairment of secondary sex characteristics, Parasites increase their own fitness by exploiting hosts for resources necessary for their survival, e. g. food, water, heat, habitat, and transmission. Although parasitism applies unambiguously to many cases, it is part of a continuum of types of interactions between species, rather than an exclusive category, in many cases, it is difficult to demonstrate harm to the host. In others, there may be no apparent specialization on the part of the parasite, coined in English in 1611, the word parasitism comes from the Greek παρά + σιτισμός feeding, fattening. Parasites are classified based on their interactions with their hosts and on their life cycles, an obligate parasite is totally dependent on the host to complete its life cycle, while a facultative parasite is not. A direct parasite has one host while an indirect parasite has multiple hosts. For indirect parasites, there always be a definitive host. Parasites that live on the outside of the host, either on the skin or the outgrowths of the skin, are called ectoparasites and those that live inside the host are called endoparasites. Endoparasites can exist in one of two forms, intercellular parasites or intracellular parasites, intracellular parasites, such as protozoa, bacteria or viruses, tend to rely on a third organism, which is generally known as the carrier or vector. The vector does the job of transmitting them to the host, an example of this interaction is the transmission of malaria, caused by a protozoan of the genus Plasmodium, to humans by the bite of an anopheline mosquito. Those parasites living in a position, being half-ectoparasites and half-endoparasites, are called mesoparasites. An epiparasite is one that feeds on another parasite and this relationship is also sometimes referred to as hyperparasitism, exemplified by a protozoan living in the digestive tract of a flea living on a dog. Social parasites take advantage of interactions between members of social organisms such as ants, termites, and bumblebees, an extreme example of social parasitism is the ant species of Tetramorium inquilinum of the Alps, which spend their whole lives on the back of Tetramorium host ants. With tiny and deprecated bodies they have evolved for one single task, if they fall off, they most likely would not have the strength to climb back on top of another ant, and eventually they will die
13.
Chitin
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Chitin n is a long-chain polymer of an N-acetylglucosamine, a derivative of glucose, and is found in many places throughout the natural world. The structure of chitin is comparable to the cellulose, forming crystalline nanofibrils or whiskers. In terms of function, it may be compared to the protein keratin, chitin has proved versatile for several medicinal, industrial and biotechnological purposes. The English word chitin comes from the French word chitine, which first appeared in 1821 and derived from the Greek word χιτών, a similar word, chiton, refers to a marine animal with a protective shell. The structure of chitin was solved by Albert Hofmann in 1929, chitin is a modified polysaccharide that contains nitrogen, it is synthesized from units of N-acetyl-D-glucosamine. Therefore, chitin may be described as cellulose with one group on each monomer replaced with an acetyl amine group. This allows for increased hydrogen bonding between adjacent polymers, giving the chitin-polymer matrix increased strength, in its pure, unmodified form, chitin is translucent, pliable, resilient, and quite tough. Combined with calcium carbonate, as in the shells of crustaceans and molluscs and this composite material is much harder and stiffer than pure chitin, and is tougher and less brittle than pure calcium carbonate. Another difference between pure and composite forms can be seen by comparing the body wall of a caterpillar to the stiff. The elaborate chitin gyroid construction in butterfly wings creates a model of optical devices having potential for innovations in biomimicry, scarab beetles in the genus Cyphochilus also utilize chitin to form extremely thin scales that diffusely reflect white light. These scales are networks of randomly ordered filaments of chitin with diameters on the scale of hundreds of nanometres, the multiple scattering of light is thought to play a role in the unusual whiteness of the scales. In addition, some wasps, such as Protopolybia chartergoides, orally secrete material containing predominantly chitin to reinforce the outer nest envelopes. Chitosan is produced commercially by deacetylation of chitin, chitosan is soluble in water, chitin producing organisms like protozoa, fungi, arthropods, and nematodes are often pathogens in other species. Keratinocytes in skin can also react to chitin or chitin fragments, according to in vitro studies, chitin is sensed by receptors, such as FIBCD1, KLRB1, REG3G, Toll-like receptor 2, CLEC7A, and mannose receptors. Plants also have receptors that can cause a response to chitin, namely chitin elicitor receptor kinase 1, the first chitin receptor was cloned in 2006. When the receptors are activated by chitin, genes related to plant defense are expressed, and jasmonate hormones are activated, commensal fungi that have ways to interact with the host immune response that as of 2016 were not well understood. Some pathogens produce chitin-binding proteins that mask the chitin they shed from these receptors, zymoseptoria tritici is an example of a fungal pathogen that has such blocking proteins, it is a major pest in wheat crops. Chitin was probably present in the exoskeletons of Cambrian arthropods such as trilobites, the oldest preserved chitin dates to the Oligocene, about 25 million years ago, consisting of a scorpion encased in amber
14.
Cell wall
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A cell wall is a structural layer surrounding some types of cells, situated outside the cell membrane. It can be tough, flexible, and sometimes rigid and it provides the cell with both structural support and protection, and also acts as a filtering mechanism. Cell walls are present in most prokaryotes, in algae, plants and fungi, a major function is to act as pressure vessels, preventing over-expansion of the cell when water enters. The composition of cell walls varies between species and may depend on type and developmental stage. The primary cell wall of plants is composed of the polysaccharides cellulose, hemicellulose. Often, other such as lignin, suberin or cutin are anchored to or embedded in plant cell walls. Algae possess walls made of glycoproteins and polysaccharides such as carrageenan, in bacteria, the cell wall is composed of peptidoglycan. The cell walls of archaea have various compositions, and may be formed of glycoprotein S-layers, pseudopeptidoglycan, Fungi possess cell walls made of the glucosamine polymer chitin. Unusually, diatoms have a wall composed of biogenic silica. A plant cell wall was first observed and named by Robert Hooke in 1665, in 1804, Karl Rudolphi and J. H. F. Link proved that cells had independent cell walls, before, it had been thought that cells shared walls and that fluid passed between them this way. The mode of formation of the wall was controversial in the 19th century. Hugo von Mohl advocated the idea that the wall grows by apposition. Carl Nägeli believed that the growth of the wall in thickness, each theory was improved in the following decades, the apposition theory by Eduard Strasburger, and the intussusception theory by Julius Wiesner. In 1930, Ernst Münch coined the term apoplast in order to separate the living symplast from the dead plant region, Cell walls serve similar purposes in those organisms that possess them. They may give cells rigidity and strength, offering protection against mechanical stress, in multicellular organisms, they permit the organism to build and hold a definite shape. Cell walls also limit the entry of large molecules that may be toxic to the cell and they further permit the creation of stable osmotic environments by preventing osmotic lysis and helping to retain water. Their composition, properties, and form may change during the cell cycle, in most cells, the cell wall is flexible, meaning that it will bend rather than holding a fixed shape, but has considerable tensile strength
15.
Chytridiomycota
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Chytridiomycota is a division of zoosporic organisms in the kingdom Fungi, informally known as chytrids. The name is derived from the Greek χυτρίδιον chytridion, meaning little pot, chytrids are saprobic, degrading refractory materials such as chitin and keratin, and sometimes act as parasites. There has been a significant increase in the research of chytrids since the discovery of Batrachochytrium dendrobatidis, species of Chytridiomycota have traditionally been delineated and classified based on development, morphology, substrate, and method of zoospore discharge. However, single spore isolates display a great amount of variation in many of features, thus. Currently, taxonomy in Chytridiomycota is based on data, zoospore ultrastructure and some aspects of thallus morphology. In an older and more restricted sense, the term chytrids referred just to those fungi in the class Chytridiomycetes, here, the term “chytrid” refers to all members of Chytridiomycota. The chytrids have also included among the Protoctista, but are now regularly classed as fungi. In older classifications, chytrids, except the recently established order Spizellomycetales, were placed in the class Phycomycetes under the subphylum Myxomycophyta of the kingdom Fungi, previously, they were placed in the Mastigomycotina as the class Chytridiomycetes. The other classes of the Mastigomycotina, the Hyphochytriomycetes and Oomycetes, the class Chytridiomycetes has over 750 chytrid species distributed among ten orders. Additional classes include the Monoblepharidomycetes, with two orders, and the Hyaloraphidiomycetes with a single order, the Olpidiaceae, including the type genus Olpidium, formerly classified in the order Chytridiales, were raised to a separate phylum, the Olpidiomycota. Chytridiomycota are unusual among the Fungi in that they reproduce with zoospores, for most members of Chytridiomycetes, sexual reproduction is not known. Asexual reproduction occurs through the release of zoospores derived through mitosis, where it has been described, sexual reproduction of Chytridomycetes occurs via a variety of methods. It is generally accepted that the zygote forms a resting spore. In some members, sexual reproduction is achieved through the fusion of isogametes and this group includes the notable plant pathogens Synchytrium. Some algal parasites practice oogamy, a male gamete attaches itself to a nonmotile structure containing the female gamete. In another group, two thalli produce tubes that fuse and allow the gametes to meet and fuse, in the last group, rhizoids of compatible strains meet and fuse. Both nuclei migrate out of the zoosporangium and into the conjoined rhizoids where they fuse, the resulting zygote germinates into a resting spore. Sexual reproduction is common and well known members of the Monblepharidomycetes
16.
Flagellum
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A flagellum is a lash-like appendage that protrudes from the cell body of certain prokaryotic and eukaryotic cells. The word flagellum in Latin means whip, the primary role of the flagellum is locomotion, but it also often has function as a sensory organelle, being sensitive to chemicals and temperatures outside the cell. Flagella are organelles defined by function rather than structure, large differences occur between different types of flagella, the prokaryotic and eukaryotic flagella differ greatly in protein composition, structure, and mechanism of propulsion. However, both can be used for swimming, an example of a flagellated bacterium is the ulcer-causing Helicobacter pylori, which uses multiple flagella to propel itself through the mucus lining to reach the stomach epithelium. An example of a eukaryotic cell is the mammalian sperm cell. Eukaryotic flagella are structurally identical to eukaryotic cilia, although distinctions are made according to function and/or length. Fimbriae and pili are also thin appendages, but have different functions and are usually smaller, three types of flagella have so far been distinguished, bacterial, archaeal, and eukaryotic. The main differences among these three types are, Bacterial flagella are helical filaments, each with a motor at its base which can turn clockwise or counterclockwise. They provide two of several kinds of bacterial motility, archaeal flagella are superficially similar to bacterial flagella, but are different in many details and considered non-homologous. Eukaryotic flagella—those of animal, plant, and protist cells—are complex cellular projections that lash back, eukaryotic flagella are classed along with eukaryotic motile cilia as undulipodia to emphasize their distinctive wavy appendage role in cellular function or motility. Primary cilia are immotile, and are not undulipodia, they have a structurally different 9+0 axoneme rather than the 9+2 axoneme found in both flagella and motile cilia undulipodia, the bacterial flagellum is made up of the protein flagellin. Its shape is a 20-nanometer-thick hollow tube and it is helical and has a sharp bend just outside the outer membrane, this hook allows the axis of the helix to point directly away from the cell. A shaft runs between the hook and the body, passing through protein rings in the cells membrane that act as bearings. Gram-positive organisms have two of these basal body rings, one in the layer and one in the plasma membrane. The filament ends with a capping protein, the flagellar filament is the long, helical screw that propels the bacterium when rotated by the motor, through the hook. Each protofilament is a series of protein chains. However, Campylobacter jejuni has seven protofilaments, the basal body has several traits in common with some types of secretory pores, such as the hollow, rod-like plug in their centers extending out through the plasma membrane. The bacterial flagellum is driven by an engine made up of protein
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Zoospore
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A zoospore is a motile asexual spore that uses a flagellum for locomotion. Also called a spore, these spores are created by some protists, bacteria. Zoospores may possess one or more types of flagella, tinsel or decorated. Whiplash flagella are straight, to power the zoospore through its medium, there is also the default zoospore, which only has the propelling, whiplash flagella. Both tinsel and whiplash flagella beat in a wave pattern. In eukaryotes there are four types of zoospore, illustrated in Fig.1 at right. Posterior whiplash flagella, a characteristic of Chytridiomycota, and a proposed a uniting trait of the Opisthokonts, in most of these, there is a single posterior flagellum, but in Neocallimastigales, there are up to 16 Anisokont. Biflagellate zoospores with two whip type flagella of unequal length and these are found in some Myxomycota and Plasmodiophoromycota. Zoospores with a single anterior flagellum of the type, characteristic of Hyphochytriomycetes. Biflagellate zoospores with both whiplash and tinsel type flagella attached anteriorly or laterally and these Zoospores are characteristic of Oomycota and other Heterokonts. Introductory Mycology, 4th ed. ISBN 0-471-52229-5
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Hypha
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A hypha is a long, branching filamentous structure of a fungus, oomycete, or actinobacterium. In most fungi, hyphae are the mode of vegetative growth. Yeasts are unicellular fungi that do not grow as hyphae, a hypha consists of one or more cells surrounded by a tubular cell wall. In most fungi, hyphae are divided into cells by internal cross-walls called septa, septa are usually perforated by pores large enough for ribosomes, mitochondria and sometimes nuclei to flow between cells. The major structural polymer in fungal cell walls is typically chitin, in contrast to plants, some fungi have aseptate hyphae, meaning their hyphae are not partitioned by septa. Hyphae have a diameter of 4-6 µm. During tip growth, cell walls are extended by the assembly and polymerization of cell wall components. The spitzenkörper is an intracellular organelle associated with tip growth and it is composed of an aggregation of membrane-bound vesicles containing cell wall components. The spitzenkörper is part of the system of fungi, holding and releasing vesicles it receives from the Golgi apparatus. These vesicles travel to the membrane via the cytoskeleton and release their contents outside the cell by the process of exocytosis. Vesicle membranes contribute to growth of the membrane while their contents form new cell wall. As a hypha extends, septa may be formed behind the tip to partition each hypha into individual cells. Hyphae can branch through the bifurcation of a tip, or by the emergence of a new tip from an established hypha. The direction of growth can be controlled by environmental stimuli. Hyphae can sense reproductive units from some distance, and grow towards them, hyphae can weave through a permeable surface to penetrate it. Hyphae may be modified in different ways to serve specific functions. Some parasitic fungi form haustoria that function in absorption within the host cells, the arbuscules of mutualistic mycorrhizal fungi serve a similar function in nutrient exchange, so are important in assisting nutrient and water absorption by plants. Hyphae are found enveloping the gonidia in lichens, making up a part of their structure
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Dikarya
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The Dikarya are most of the so-called higher fungi, but also include many anamorphic species that would have been classified as molds in historical literature. Phylogenetically the two divisions regularly group together, in a 1998 publication, Thomas Cavalier-Smith referred to this group as the Neomycota. The 2007 classification of Kingdom Fungi is the result of a collaborative research effort involving dozens of mycologists. It recognizes seven divisions within the Fungi, two of which—the Ascomycota and the Basidiomycota—are contained within a branch representing subkingdom Dikarya, the cladogram depicts the major fungal taxa and their relationship to opisthokont and unikont organisms. The lengths of the branches in this tree are not proportional to evolutionary distances, list of fungal orders AFTOL classification at Dave Hibbetts site
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Ascomycota
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Ascomycota is a division or phylum of the kingdom Fungi that, together with the Basidiomycota, form the subkingdom Dikarya. Its members are known as the sac fungi or ascomycetes. They are the largest phylum of Fungi, with over 64,000 species, the defining feature of this fungal group is the ascus, a microscopic sexual structure in which nonmotile spores, called ascospores, are formed. However, some species of the Ascomycota are asexual, meaning that they do not have a sexual cycle, the ascomycetes are a monophyletic group, i. e. it contains all descendants of one common ancestor. Familiar examples of sac fungi include morels, truffles, brewers yeast and bakers yeast, dead mans fingers, the fungal symbionts in the majority of lichens such as Cladonia belong to the Ascomycota. There are many plant-pathogenic ascomycetes, including apple scab, rice blast, the fungi, black knot. Several species of ascomycetes are biological model organisms in laboratory research, most famously, Neurospora crassa, several species of yeasts, and Aspergillus species are used in many genetics and cell biology studies. Penicillium species on cheeses and those producing antibiotics for treating infectious diseases are examples of taxa that belong to the Ascomycota. They are fungi which produce microscopic spores inside special, elongated cells or sacs, known as asci, Asexual reproduction, Asexual reproduction is the dominant form of propagation in the Ascomycota, and is responsible for the rapid spread of these fungi into new areas. Asexual reproduction of ascomycetes is very diverse from both structural and functional points of view, the most important and general is production of conidia, but chlamydospores are also frequently produced. Furthermore, Ascomycota also reproduce asexually through budding, 1) Conidia formation, Asexual reproduction may occur through vegetative reproductive spores, the conidia. Asexual, non-motile haploid spore of a fungus, which is named after the Greek word for dust, conia and they are typically formed at the ends of specialized hyphae, the conidiophores. Depending on the species they may be dispersed by wind or water, conidiophores may simply branch off from the mycelia or they may be formed in fruiting bodies. The hypha that creates the sporing tip can be similar to the normal hyphal tip. The most common differentiation is the formation of a bottle shaped cell called a phialide, as all of these asexual structures are not single hyphae. In some groups, the conidiophores are aggregated to form a thick structure, in the order Moniliales, all of them are single hyphae with the exception of the aggregations, termed as coremia or synnema. These produce structures rather like corn-stokes, with many conidia being produced in a mass from the aggregated conidiophores, the diverse conidia and conidiophores sometimes develop in asexual sporocarps with different characteristics. Some species of Ascomycetes form their structures within plant tissue, either as parasite or saprophytes and these fungi have evolved more complex asexual sporing structures, probably influenced by the cultural conditions of plant tissue as a substrate
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Basidiomycota
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Basidiomycota is one of two large divisions that, together with the Ascomycota, constitute the subkingdom Dikarya within the kingdom Fungi. Basidiomycota are filamentous fungi composed of hyphae and reproduce sexually via the formation of specialized club-shaped end cells called basidia that normally bear external meiospores and these specialized spores are called basidiospores. However, some Basidiomycota reproduce asexually in addition or exclusively, the most recent classification adopted by a coalition of 67 mycologists recognizes three subphyla and two other class level taxa outside of these, among the Basidiomycota. As now classified, the join and also cut across various obsolete taxonomic groups previously commonly used to describe Basidiomycota. According to a 2008 estimate, Basidiomycota comprise three subphyla 16 classes,52 orders,177 families,1,589 genera, and 31,515 species, the terms basidiomycetes and ascomycetes are frequently used loosely to refer to Basidiomycota and Ascomycota. They are often abbreviated to basidios and ascos as mycological slang, the Agaricomycotina include what had previously been called the Hymenomycetes, the Gasteromycetes, as well as most of the jelly fungi. The three classes in the Agaricomycotina are the Agaricomycetes, the Dacrymycetes, and the Tremellomycetes, the class Wallemiomycetes is not yet placed in a subdivision, but recent genomic evidence suggests that it is a sister group of Agaricomycotina. The Ustilaginomycotina are most of the former smut fungi and the Exobasidiales, the classes of the Ustilaginomycotina are the Exobasidiomycetes, the Entorrhizomycetes, and the Ustilaginomycetes. Typically haploid Basidiomycota mycelia fuse via plasmogamy and then the compatible nuclei migrate into each others mycelia, karyogamy is delayed, so that the compatible nuclei remain in pairs, called a dikaryon. The hyphae are said to be dikaryotic. Conversely, the mycelia are called monokaryons. Often, the mycelium is more vigorous than the individual monokaryotic mycelia. The dikaryons can be long-lived, lasting years, decades, or centuries, the monokaryons are neither male nor female. They have either a bipolar or a mating system. However, there are variations of these genes in the population. It is as if there were multiple sexes, meiosis follows shortly with the production of 4 haploid nuclei that migrate into 4 external, usually apical basidiospores. Typically the basidiospores are ballistic, hence they are also called ballistospores. In most species, the basidiospores disperse and each can start a new haploid mycelium, basidia are microscopic but they are often produced on or in multicelled large fructifications called basidiocarps or basidiomes, or fruitbodies), variously called mushrooms, puffballs, etc
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Yeast
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Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom. The yeast lineage originated hundreds of millions of years ago, and 1,500 species are currently identified and they are estimated to constitute 1% of all described fungal species. Yeast sizes vary greatly, depending on species and environment, typically measuring 3–4 µm in diameter, most yeasts reproduce asexually by mitosis, and many do so by the asymmetric division process known as budding. Yeasts, with their growth habit, can be contrasted with molds. Fungal species that can take both forms are called dimorphic fungi and it is also a centrally important model organism in modern cell biology research, and is one of the most thoroughly researched eukaryotic microorganisms. Researchers have used it to information about the biology of the eukaryotic cell. Other species of yeasts, such as Candida albicans, are opportunistic pathogens, yeasts have recently been used to generate electricity in microbial fuel cells, and produce ethanol for the biofuel industry. Yeasts do not form a taxonomic or phylogenetic grouping. The budding yeasts are classified in the order Saccharomycetales, within the phylum Ascomycota, the word yeast comes from Old English gist, gyst, and from the Indo-European root yes-, meaning boil, foam, or bubble. Yeast microbes are probably one of the earliest domesticated organisms, archaeologists digging in Egyptian ruins found early grinding stones and baking chambers for yeast-raised bread, as well as drawings of 4, 000-year-old bakeries and breweries. In 1680, Dutch naturalist Anton van Leeuwenhoek first microscopically observed yeast, but at the time did not consider them to be living organisms, researchers were doubtful whether yeasts were algae or fungi, but in 1837 Theodor Schwann recognized them as fungi. In 1857, French microbiologist Louis Pasteur proved in the paper Mémoire sur la fermentation alcoolique that alcoholic fermentation was conducted by living yeasts and not by a chemical catalyst. Pasteur showed that by bubbling oxygen into the yeast broth, cell growth could be increased, by the late 18th century, two yeast strains used in brewing had been identified, Saccharomyces cerevisiae and S. carlsbergensis. S. cerevisiae has been sold commercially by the Dutch for bread-making since 1780, while, around 1800, in 1825, a method was developed to remove the liquid so the yeast could be prepared as solid blocks. The industrial production of yeast blocks was enhanced by the introduction of the press in 1867. In 1872, Baron Max de Springer developed a process to create granulated yeast. Yeasts are chemoorganotrophs, as they use organic compounds as a source of energy, carbon is obtained mostly from hexose sugars, such as glucose and fructose, or disaccharides such as sucrose and maltose. Some species can metabolize pentose sugars such as ribose, alcohols, Yeast species either require oxygen for aerobic cellular respiration or are anaerobic, but also have aerobic methods of energy production
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Saccharomyces cerevisiae
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Saccharomyces cerevisiae is a species of yeast. It has been instrumental to winemaking, baking, and brewing since ancient times and it is believed to have been originally isolated from the skin of grapes. It is one of the most intensively studied model organisms in molecular and cell biology. It is the microorganism behind the most common type of fermentation, S. cerevisiae cells are round to ovoid, 5–10 μm in diameter. It reproduces by a process known as budding. Many proteins important in biology were first discovered by studying their homologs in yeast, these proteins include cell cycle proteins, signaling proteins. S. cerevisiae is currently the only yeast cell known to have Berkeley bodies present, antibodies against S. cerevisiae are found in 60–70% of patients with Crohns disease and 10–15% of patients with ulcerative colitis. Saccharomyces derives from Latinized Greek and means sugar-mold or sugar-fungus, saccharo being the combining form sugar, cerevisiae comes from Latin and means of beer. Refinements in microbiology following the work of Louis Pasteur led to more advanced methods of culturing pure strains, in 1879, Great Britain introduced specialized growing vats for the production of S. The company created yeast that would rise twice as fast, cutting down on baking time, lesaffre would later create instant yeast in the 1970s, which has gained considerable use and market share at the expense of both fresh and dry yeast in their various applications. In nature, yeast cells are primarily on ripe fruits such as grapes. Since S. cerevisiae is not airborne, it requires a vector to move, queens of social wasps overwintering as adults can harbor yeast cells from autumn to spring and transmit them to their progeny. The intestine of Polistes dominula, a wasp, hosts S. cerevisiae strains as well as S. cerevisiae × S. paradoxus hybrids. The optimum temperature for growth of S. cerevisiae is 30–35 °C, two forms of yeast cells can survive and grow, haploid and diploid. The haploid cells undergo a simple lifecycle of mitosis and growth and this is the asexual form of the fungus. The diploid cells undergo a simple lifecycle of mitosis and growth. The rate at which the cell cycle progresses often differs substantially between haploid and diploid cells. Under conditions of stress, diploid cells can undergo sporulation, entering meiosis and producing four haploid spores and this is the sexual form of the fungus
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Phylogenetic tree
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The taxa joined together in the tree are implied to have descended from a common ancestor. Phylogenetic trees are central to the field of phylogenetics, each node is called a taxonomic unit. Internal nodes are generally called hypothetical taxonomic units, as they cannot be directly observed, Trees are useful in fields of biology such as bioinformatics, systematics, and phylogenetic comparative methods. Unrooted trees illustrate only the relatedness of the nodes and do not require the ancestral root to be known or inferred. The idea of a tree of life arose from ancient notions of a progression from lower to higher forms of life. Charles Darwin also produced one of the first illustrations and crucially popularized the notion of a tree in his seminal book The Origin of Species. Over time, species classification has become static and more dynamic. A rooted phylogenetic tree is a tree with a unique node corresponding to the most recent common ancestor of all the entities at the leaves of the tree. The most common method for rooting trees is the use of an uncontroversial outgroup—close enough to allow inference from trait data or molecular sequencing, unrooted trees illustrate the relatedness of the leaf nodes without making assumptions about ancestry. They do not require the ancestral root to be known or inferred, unrooted trees can always be generated from rooted ones by simply omitting the root. By contrast, inferring the root of an unrooted tree requires some means of identifying ancestry, both rooted and unrooted phylogenetic trees can be either bifurcating or multifurcating, and either labeled or unlabeled. In contrast, a rooted multifurcating tree may have more than two children at some nodes and an unrooted multifurcating tree may have more than three neighbors at some nodes. A labeled tree has specific values assigned to its leaves, while a tree, sometimes called a tree shape. The last distinction is the most biologically relevant, it arises because there are places on an unrooted tree to put the root. For labeled bifurcating trees, there are,2 n −2. for n ≥2 total rooted trees and. 2 n −3. for n ≥3 total unrooted trees, among labeled bifurcating trees, the number of unrooted trees with n leaves is equal to the number of rooted trees with n −1 leaves. A dendrogram is a term for the diagrammatic representation of a phylogenetic tree. A cladogram is a phylogenetic tree formed using cladistic methods and this type of tree only represents a branching pattern, i. e. its branch spans do not represent time or relative amount of character change
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Mesomycetozoea
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The Mesomycetozoea are a small group of Opisthokonta in Eukarya, mostly parasites of fish and other animals. However, they form a coherent group on molecular trees, closely related to animals and fungi and so of interest to biologists studying their origins. In a 2008 study they emerge robustly as the sister-group of the clade Filozoa, huldtgren et al. following x-ray tomography of microfossils of the Ediacaran Doushantuo Formation, has interpreted them as mesomycetozoan spore capsules. The name DRIP is an acronym for the first protozoa identified as members of the group, Cavalier-Smith later treated them as the class Ichthyosporea, one species, Rhinosporidium seeberi, infects birds and mammals, including humans. On Eukaryota tree, in Opisthokont clade, Mesomycetozoea is in the middle of the fungi, note the name Mesomycetozoa is also used to refer to this group, but Mendoza et al. use it as an alternate name for the phylum Choanozoa
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Filozoa
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The Filozoa are a monophyletic grouping within the Opisthokonta. They include animals and their nearest unicellular relatives, the most up to date cladogram is The ancestral opisthokont cell is assumed to have possessed slender filose projections or tentacles. In some opisthokonts these were lost and they are retained in Filozoa, where they are simple and non-tapering, with a rigid core of actin bundles
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Choanoflagellate
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The choanoflagellates are a group of free-living unicellular and colonial flagellate eukaryotes considered to be the closest living relatives of the animals. Choanoflagellates are collared flagellates having a funnel shaped collar of interconnected microvilli at the base of a flagellum and they have a distinctive cell morphology characterized by an ovoid or spherical cell body 3–10 µm in diameter with a single apical flagellum surrounded by a collar of 30–40 microvilli. This feeding provides a link within the global carbon cycle. In addition to their ecological roles, choanoflagellates are of particular interest to evolutionary biologists studying the origins of multicellularity in animals. As the closest living relatives of animals, choanoflagellates serve as a model for reconstructions of the last unicellular ancestor of animals. From Greek Khoanē meaning funnel and the Latin word flagellum, each choanoflagellate has a single flagellum, surrounded by a ring of actin-filled protrusions called microvilli, forming a cylindrical or conical collar. Movement of the flagellum draws water through the collar, and bacteria and detritus are captured by the microvilli, water currents generated by the flagellum also push free-swimming cells along, as in animal sperm. In contrast, most other flagellates are pulled by their flagella, in addition to the single apical flagellum surrounded by actin-filled microvilli that characterizes choanoflagellates, the internal organization of organelles in the cytoplasm is constant. A flagellar basal body sits at the base of the flagellum. The nucleus occupies a position in the cell, and food vacuoles are positioned in the basal region of the cytoplasm. Additionally, the body of many choanoflagellates is surrounded by a distinguishing extracellular matrix or periplast. These cell coverings vary greatly in structure and composition and are used by taxonomists for classification purposes, many choanoflagellates build complex basket-shaped houses, called lorica, from several silica strips cemented together. The functional significance of the periplast is unknown, but in sessile organisms, in planktonic organisms, there is speculation that the periplast increases drag, thereby counteracting the force generated by the flagellum and increasing feeding efficiency. Choanoflagellates are either free-swimming in the column or sessile, adhering to the substrate directly or through either the periplast or a thin pedicel. The life histories of choanoflagellates are poorly understood, many species are thought to be solitary, however coloniality seems to have arisen independently several times within the group and colonial species retain a solitary stage. Choanoflagellates grow vegetatively, with many species undergoing longitudinal fission, however, interestingly, some choanoflagellates can undergo encystment, which involves the retraction of the flagellum and collar and encasement in an electron dense fibrillar wall. On transfer to fresh media, excystment occurs, though it remains to be directly observed, further examination of the choanoflagellate life cycle will be informative about mechanisms of colony formation and attributes present before the evolution of animal multicellularity. The choanoflagellates were included in Chrysophyceae until Hibberd,1975, recent molecular phylogenetic reconstruction of the internal relationships of choanoflagellates allows the polarization of character evolution within the clade
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Animal
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Animals are multicellular, eukaryotic organisms of the kingdom Animalia. The animal kingdom emerged as a clade within Apoikozoa as the group to the choanoflagellates. Animals are motile, meaning they can move spontaneously and independently at some point in their lives and their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later in their lives. All animals are heterotrophs, they must ingest other organisms or their products for sustenance, most known animal phyla appeared in the fossil record as marine species during the Cambrian explosion, about 542 million years ago. Animals can be divided broadly into vertebrates and invertebrates, vertebrates have a backbone or spine, and amount to less than five percent of all described animal species. They include fish, amphibians, reptiles, birds and mammals, the remaining animals are the invertebrates, which lack a backbone. These include molluscs, arthropods, annelids, nematodes, flatworms, cnidarians, ctenophores, the study of animals is called zoology. The word animal comes from the Latin animalis, meaning having breath, the biological definition of the word refers to all members of the kingdom Animalia, encompassing creatures as diverse as sponges, jellyfish, insects, and humans. Aristotle divided the world between animals and plants, and this was followed by Carl Linnaeus, in the first hierarchical classification. In Linnaeuss original scheme, the animals were one of three kingdoms, divided into the classes of Vermes, Insecta, Pisces, Amphibia, Aves, and Mammalia. Since then the last four have all been subsumed into a single phylum, in 1874, Ernst Haeckel divided the animal kingdom into two subkingdoms, Metazoa and Protozoa. The protozoa were later moved to the kingdom Protista, leaving only the metazoa, thus Metazoa is now considered a synonym of Animalia. Animals have several characteristics that set apart from other living things. Animals are eukaryotic and multicellular, which separates them from bacteria and they are heterotrophic, generally digesting food in an internal chamber, which separates them from plants and algae. They are also distinguished from plants, algae, and fungi by lacking cell walls. All animals are motile, if only at life stages. In most animals, embryos pass through a stage, which is a characteristic exclusive to animals. With a few exceptions, most notably the sponges and Placozoa and these include muscles, which are able to contract and control locomotion, and nerve tissues, which send and process signals
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PubMed Identifier
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PubMed is a free search engine accessing primarily the MEDLINE database of references and abstracts on life sciences and biomedical topics. The United States National Library of Medicine at the National Institutes of Health maintains the database as part of the Entrez system of information retrieval, from 1971 to 1997, MEDLINE online access to the MEDLARS Online computerized database primarily had been through institutional facilities, such as university libraries. PubMed, first released in January 1996, ushered in the era of private, free, home-, the PubMed system was offered free to the public in June 1997, when MEDLINE searches via the Web were demonstrated, in a ceremony, by Vice President Al Gore. Information about the journals indexed in MEDLINE, and available through PubMed, is found in the NLM Catalog. As of 5 January 2017, PubMed has more than 26.8 million records going back to 1966, selectively to the year 1865, and very selectively to 1809, about 500,000 new records are added each year. As of the date,13.1 million of PubMeds records are listed with their abstracts. In 2016, NLM changed the system so that publishers will be able to directly correct typos. Simple searches on PubMed can be carried out by entering key aspects of a subject into PubMeds search window, when a journal article is indexed, numerous article parameters are extracted and stored as structured information. Such parameters are, Article Type, Secondary identifiers, Language, publication type parameter enables many special features. As these clinical girish can generate small sets of robust studies with considerable precision, since July 2005, the MEDLINE article indexing process extracts important identifiers from the article abstract and puts those in a field called Secondary Identifier. The secondary identifier field is to store numbers to various databases of molecular sequence data, gene expression or chemical compounds. For clinical trials, PubMed extracts trial IDs for the two largest trial registries, ClinicalTrials. gov and the International Standard Randomized Controlled Trial Number Register, a reference which is judged particularly relevant can be marked and related articles can be identified. If relevant, several studies can be selected and related articles to all of them can be generated using the Find related data option, the related articles are then listed in order of relatedness. To create these lists of related articles, PubMed compares words from the title and abstract of each citation, as well as the MeSH headings assigned, using a powerful word-weighted algorithm. The related articles function has been judged to be so precise that some researchers suggest it can be used instead of a full search, a strong feature of PubMed is its ability to automatically link to MeSH terms and subheadings. Examples would be, bad breath links to halitosis, heart attack to myocardial infarction, where appropriate, these MeSH terms are automatically expanded, that is, include more specific terms. Terms like nursing are automatically linked to Nursing or Nursing and this important feature makes PubMed searches automatically more sensitive and avoids false-negative hits by compensating for the diversity of medical terminology. The My NCBI area can be accessed from any computer with web-access, an earlier version of My NCBI was called PubMed Cubby
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International Standard Serial Number
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An International Standard Serial Number is an eight-digit serial number used to uniquely identify a serial publication. The ISSN is especially helpful in distinguishing between serials with the same title, ISSN are used in ordering, cataloging, interlibrary loans, and other practices in connection with serial literature. The ISSN system was first drafted as an International Organization for Standardization international standard in 1971, ISO subcommittee TC 46/SC9 is responsible for maintaining the standard. When a serial with the content is published in more than one media type. For example, many serials are published both in print and electronic media, the ISSN system refers to these types as print ISSN and electronic ISSN, respectively. The format of the ISSN is an eight digit code, divided by a hyphen into two four-digit numbers, as an integer number, it can be represented by the first seven digits. The last code digit, which may be 0-9 or an X, is a check digit. Formally, the form of the ISSN code can be expressed as follows, NNNN-NNNC where N is in the set, a digit character. The ISSN of the journal Hearing Research, for example, is 0378-5955, where the final 5 is the check digit, for calculations, an upper case X in the check digit position indicates a check digit of 10. To confirm the check digit, calculate the sum of all eight digits of the ISSN multiplied by its position in the number, the modulus 11 of the sum must be 0. There is an online ISSN checker that can validate an ISSN, ISSN codes are assigned by a network of ISSN National Centres, usually located at national libraries and coordinated by the ISSN International Centre based in Paris. The International Centre is an organization created in 1974 through an agreement between UNESCO and the French government. The International Centre maintains a database of all ISSNs assigned worldwide, at the end of 2016, the ISSN Register contained records for 1,943,572 items. ISSN and ISBN codes are similar in concept, where ISBNs are assigned to individual books, an ISBN might be assigned for particular issues of a serial, in addition to the ISSN code for the serial as a whole. An ISSN, unlike the ISBN code, is an identifier associated with a serial title. For this reason a new ISSN is assigned to a serial each time it undergoes a major title change, separate ISSNs are needed for serials in different media. Thus, the print and electronic versions of a serial need separate ISSNs. Also, a CD-ROM version and a web version of a serial require different ISSNs since two different media are involved, however, the same ISSN can be used for different file formats of the same online serial
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International Standard Book Number
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The International Standard Book Number is a unique numeric commercial book identifier. An ISBN is assigned to each edition and variation of a book, for example, an e-book, a paperback and a hardcover edition of the same book would each have a different ISBN. The ISBN is 13 digits long if assigned on or after 1 January 2007, the method of assigning an ISBN is nation-based and varies from country to country, often depending on how large the publishing industry is within a country. The initial ISBN configuration of recognition was generated in 1967 based upon the 9-digit Standard Book Numbering created in 1966, the 10-digit ISBN format was developed by the International Organization for Standardization and was published in 1970 as international standard ISO2108. Occasionally, a book may appear without a printed ISBN if it is printed privately or the author does not follow the usual ISBN procedure, however, this can be rectified later. Another identifier, the International Standard Serial Number, identifies periodical publications such as magazines, the ISBN configuration of recognition was generated in 1967 in the United Kingdom by David Whitaker and in 1968 in the US by Emery Koltay. The 10-digit ISBN format was developed by the International Organization for Standardization and was published in 1970 as international standard ISO2108, the United Kingdom continued to use the 9-digit SBN code until 1974. The ISO on-line facility only refers back to 1978, an SBN may be converted to an ISBN by prefixing the digit 0. For example, the edition of Mr. J. G. Reeder Returns, published by Hodder in 1965, has SBN340013818 -340 indicating the publisher,01381 their serial number. This can be converted to ISBN 0-340-01381-8, the check digit does not need to be re-calculated, since 1 January 2007, ISBNs have contained 13 digits, a format that is compatible with Bookland European Article Number EAN-13s. An ISBN is assigned to each edition and variation of a book, for example, an ebook, a paperback, and a hardcover edition of the same book would each have a different ISBN. The ISBN is 13 digits long if assigned on or after 1 January 2007, a 13-digit ISBN can be separated into its parts, and when this is done it is customary to separate the parts with hyphens or spaces. Separating the parts of a 10-digit ISBN is also done with either hyphens or spaces, figuring out how to correctly separate a given ISBN number is complicated, because most of the parts do not use a fixed number of digits. ISBN issuance is country-specific, in that ISBNs are issued by the ISBN registration agency that is responsible for country or territory regardless of the publication language. Some ISBN registration agencies are based in national libraries or within ministries of culture, in other cases, the ISBN registration service is provided by organisations such as bibliographic data providers that are not government funded. In Canada, ISBNs are issued at no cost with the purpose of encouraging Canadian culture. In the United Kingdom, United States, and some countries, where the service is provided by non-government-funded organisations. Australia, ISBNs are issued by the library services agency Thorpe-Bowker
. PMID 19939264.
