Ascomycota is a division or phylum Asexual reproduction in humans pdf to jpg the kingdom Fungi that, together with the Basidiomycotaform the subkingdom Dikarya. Its members are commonly known as the sac fungi or ascomycetes. It is the largest phylum of Fungi, with over 64, species. However, some species of the Ascomycota are asexualmeaning that they do not have a sexual cycle and thus do not form asci or ascospores. Previously placed in the Deuteromycota along with asexual species from other fungal taxa, asexual or anamorphic ascomycetes are now identified and classified based on morphological or physiological similarities to ascus-bearing taxaand by phylogenetic analyses of DNA sequences.
The ascomycetes are a monophyletic group, i. This group is of particular relevance to humans as sources for medicinally important compounds, such as antibiotics and for making bread, alcoholic beverages, and cheese, but also as pathogens of humans and plants.
Familiar examples of sac fungi include morelstrufflesbrewer's yeast and baker's yeastdead man's fingersand cup fungi. The fungal symbionts in the majority of lichens loosely termed "ascolichens" such as Cladonia belong to the Ascomycota. There are many plant-pathogenic ascomycetes, including apple scabrice blastthe ergot fungiblack knotand the powdery mildews. Several species of ascomycetes are biological model organisms in laboratory research.
Most famously, Neurospora crassaseveral species of yeastsand Aspergillus species are used in many genetics cell biology studies. Penicillium species on cheeses and those producing antibiotics for treating bacterial infectious diseases are examples of taxa that belong to the Ascomycota.
Ascomycetes are 'spore shooters'. They are fungi which produce microscopic spores inside special, elongated cells or sacs, known as 'asci', which give the group its name. 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. Asexual reproduction may occur through vegetative reproductive spores, the conidia. The asexual, non-motile haploid spores of a fungus, which are named after the Greek word for dust coniaare hence also known as conidiospores and mitospores. The conidiospores commonly contain one nucleus and are products of mitotic cell divisions and thus are sometimes call mitosporeswhich are genetically identical to the mycelium from which they originate.
They are typically formed at the ends of specialized hyphae, the conidiophores. Depending Asexual reproduction in humans pdf to jpg the species they may be dispersed by wind or water, or by animals. Conidiophores may simply branch off from the mycelia or they may be formed in fruiting bodies.
The hypha that creates the sporing conidiating tip can be very similar to the normal hyphal tip, or it can be differentiated. The most common differentiation is the formation of a bottle shaped cell called a phialidefrom which the spores are produced. Not all of these asexual structures are a hypha. In some groups, the conidiophores the structures that bear the conidia are aggregated to form a thick structure. In the order Asexual reproduction in humans pdf to jpg, 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 "Asexual reproduction in humans pdf to jpg" sometimes develop in asexual sporocarps with different characteristics e. Some species of Ascomycetes form their structures within plant tissue, either as parasite or saprophytes.
These fungi have evolved more complex asexual sporing structures, probably influenced by the cultural conditions of plant tissue as a substrate. These structures are called the sporodochium. This is a cushion of conidiophores created from a pseudoparenchymatous stroma in plant tissue.
The pycnidium is a globose to flask-shaped parenchymatous structure, lined on its inner wall with conidiophores. The acervulus is a flat saucer shaped bed of conidiophores produced under a plant cuticle, which eventually erupt through the cuticle for dispersal. Asexual reproduction process in ascomycetes also involves the budding which we clearly observe in yeast.
It involves the blowing out or blebbing of the hyphal tip wall. The blastic process can involve all wall layers, or there can be a new cell wall synthesized which is extruded from within the old wall.
The initial events of budding can be seen as the development of a ring of chitin around the point where the bud is about to appear. This reinforces and stabilizes the cell wall. Enzymatic activity and turgor pressure act to weaken and extrude the cell wall.
New cell wall material is incorporated during this phase. Cell contents are forced into the progeny cell, and as the final phase of mitosis ends a cell plate, the point at which a new cell wall will grow inwards from, forms. There are three subphyla that are described and accepted:. Several outdated taxon names—based on morphological features—are still occasionally used for species of the Ascomycota.
These include the following sexual teleomorphic groups, defined by the structures of their Asexual reproduction in humans pdf to jpg fruiting bodies: Hemiascomycetes included the yeasts and yeast-like fungi that have now been placed into the Saccharomycotina or Taphrinomycotinawhile the Euascomycetes included the remaining species of the Ascomycota, which are now in the Pezizomycotinaand the Neolectawhich are in the Taphrinomycotina. Some ascomycetes do not reproduce sexually or are not known to produce asci and are therefore anamorphic species.
Those anamorphs that produce conidia mitospores were previously described as mitosporic Ascomycota. Some taxonomists placed this group into a separate artificial phylumthe Deuteromycota or "Fungi Imperfecti".
Where recent molecular analyses have identified close relationships with ascus-bearing taxa, anamorphic species have been grouped into the Ascomycota, despite the absence of the defining ascus. Sexual and asexual isolates of the same species commonly carry different binomial species names, as, for example, Aspergillus nidulans and Emericella nidulansfor asexual and sexual isolates, respectively, of the same species.
Species of the Deuteromycota were classified as Coelomycetes if they produced their conidia in minute flask- or saucer-shaped conidiomata, known technically as pycnidia and acervuli.
They are mostly isolated but sometimes also appear as bundles of cells aligned in parallel described as synnematal or as cushion-shaped masses described as sporodochial. Asexual reproduction in humans pdf to jpg species "Asexual reproduction in humans pdf to jpg" as filamentous, microscopic structures called hyphae or as budding single cells yeasts. Many interconnected hyphae form a thallus usually referred to as the myceliumwhich—when visible to the naked eye macroscopic —is commonly called mold.
During sexual reproduction, many Ascomycota typically produce large of asci. The ascus is often contained in a multicellular, occasionally readily visible fruiting structure, the ascocarp also called an ascoma.
Ascocarps come in a very large variety of shapes: They can appear solitary or clustered. Their texture can likewise be very variable, including fleshy, like charcoal carbonaceousleathery, rubbery, gelatinous, slimy, powdery, or cob-web-like. Ascocarps come in multiple colors such as red, orange, yellow, brown, black, or, more rarely, green or blue.
Some ascomyceous fungi, such as Saccharomyces cerevisiaegrow as single-celled yeasts, which—during sexual reproduction—develop into an ascus, and do not form fruiting bodies. In lichenized species, the thallus of the fungus defines the shape of the symbiotic colony. Some dimorphic species, such as Candida albicanscan switch between growth as single cells and as filamentous, multicellular hyphae.
Other species are pleomorphicexhibiting asexual anamorphic as well as a sexual teleomorphic growth forms. Except for lichens, the non-reproductive vegetative mycelium of most ascomycetes is inconspicuous because it is commonly embedded in the substrate, such as soil, or grows on or inside a living host, and only the ascoma may be seen when fruiting.
Pigmentationsuch as melanin in hyphal walls, along with prolific growth on surfaces can result in visible mold colonies; examples include Cladosporium species, Asexual reproduction in humans pdf to jpg form black spots on bathroom caulking and other moist areas.
Many ascomycetes cause food spoilage, and, therefore, the pellicles or moldy layers that develop on jams, juices, and other foods are the mycelia of these species or occasionally Mucoromycotina and almost never Basidiomycota.
Sooty molds that develop on plants, especially in the tropics are the thalli of many species. Large masses of yeast cells, asci or ascus-like cells, or conidia can also form macroscopic structures.
Pneumocystis species can colonize lung cavities visible in x-rayscausing a form of pneumonia. The cell wall and septa give stability and rigidity to the hyphae and may prevent loss of cytoplasm in case of local damage to cell wall and cell membrane.
The septa commonly have a small opening in the center, which functions as a cytoplasmic connection between adjacent cells, also sometimes allowing cell-to-cell movement of nuclei within a hypha.
Vegetative hyphae of most ascomycetes contain only one nucleus per cell uninucleate hyphaebut multinucleate cells—especially in the apical regions of growing hyphae—can also be present. In common with other fungal phyla, the Ascomycota are heterotrophic organisms Asexual reproduction in humans pdf to jpg require organic compounds as energy sources. These are obtained by feeding on a variety of organic substrates including dead matter, foodstuffs, or as symbionts in or on other living organisms.
To obtain these nutrients from their surroundings, ascomycetous fungi secrete powerful digestive enzymes that break down organic substances into smaller molecules, which are then taken up into the cell. Many species live on dead plant material such as leaves, twigs, or logs. Several species colonize plants, animals, or other fungi as parasites or mutualistic symbionts and derive all their metabolic energy in form of nutrients from the tissues of their hosts.
Owing to their long evolutionary history, the Ascomycota have evolved the capacity to break down almost every organic substance. Unlike most organisms, they are able to use their own enzymes to digest plant biopolymers such as cellulose or lignin. Collagenan abundant structural protein in animals, and keratin —a protein that forms hair and nails—, can also serve as food sources.
Unusual examples include Aureobasidium pullulanswhich feeds on wall paint, and the kerosene fungus Amorphotheca resinaewhich feeds on aircraft fuel causing occasional problems for the airline industryand may sometimes block fuel pipes. The Ascomycota is characterized by a high degree of specialization; for instance, certain species of Laboulbeniales attack only one particular leg of one particular insect species.
Many Ascomycota engage in symbiotic relationships such as in lichens—symbiotic associations with green algae or cyanobacteria —in which the fungal symbiont directly obtains products of photosynthesis.
In common with many basidiomycetes and Glomeromycotasome ascomycetes form symbioses with plants by colonizing the roots to Asexual reproduction in humans pdf to jpg mycorrhizal associations. The Ascomycota also represents several carnivorous fungiwhich have developed hyphal traps to capture small protists such as amoebaeas well Asexual reproduction in humans pdf to jpg roundworms Nematodarotiferstardigradesand small arthropods such as springtails Collembola.
The Ascomycota are represented in all land ecosystems worldwide, occurring on all continents including Antarctica. The distribution of species is variable; while some are found on all continents, others, as for example the white truffle Tuber magnatumonly occur in isolated locations in Italy and Eastern Europe.
It occurs through vegetative reproductive spores, the conidia. The conidiospores commonly contain one nucleus and are products of mitotic cell Asexual reproduction in humans pdf to jpg and thus are sometimes called mitospores, which are genetically identical to the mycelium from which they originate. They are typically formed at the ends of specialized hyphaethe conidiophores.
Different types asexual spores can be identified by colour, shape, and how they are released as individual spores. Spore types can be used as taxonomic characters in the classification within the Ascomycota.
The most frequent types are the single-celled spores, which are designated amerospores. Reproduction (or procreation or breeding) is the biological process by which new individual Asexual reproduction is not limited to single-celled organisms.
The cloning Most animals (including humans) and plants reproduce sexually. . Tree of life by phuket-apartment.info Create a book · Download as PDF · Printable version.
Asexual reproduction does not involve gametes, instead parts of a mature organism may develop to new individuals.
and builds up of energy Asexual reproduction in humans pdf to jpg be used during the meiotic division.
meo phuket-apartment.info . Reproduction in Human Beings Structure. Nevertheless, physical contact between humans and scorpions usually results in a sting. JPG ( bytes). Yet the origin of sexual reproduction is not clear and it has probably evolved independently several times. In asexual species, AB can only arise when two similar mutations occur simultaneously in the same.
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