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 Pacific rockweed, Fucus distichus, in Olympic National Park
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The heterokonts or stramenopiles are a major line of eukaryotes presently containing about 10,500 known species. Olympic National Park is located in the US state of Washington, in the Olympic Peninsula. Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex Chromalveolata is a Eukaryote supergroup first proposed by Thomas Cavalier-Smith as a refinement of his kingdom Chromista, which was first The axodines are a group of unicellular Heterokont algae They characteristically have a single emergent flagellum which lacks the root structure found in related groups and Diatoms ( Greek: (dia = "through" + (temnein = "to cut" i Bolidomonas is a Genus of unicellular picoplanktonic Heterokonts It was recently ( 1999) discovered The golden algae or chrysophytes are a large group of Heterokont Algae found mostly in freshwater Eustigmatophytes are a small group (7 genera; ~12 Species) of eukaryotic Algae that includes marine, freshwater and Pelagophytes are a type of heterokont Algae. The Phaeophyceae or brown algae, (singular alga is a large group of mostly marine multicellular Algae including many Seaweeds of colder Raphidophytes are a small group of eukaryotic Algae that includes both marine and freshwater Species. The synurids are a small group of Heterokont algae found mostly in freshwater which are covered in silicate scales and spines Yellow-green algae or xanthophytes are an important group of Heterokont algae The bicosoecids are a small group of unicellular Flagellates included among the Heterokonts The cells are free-living with no Chloroplasts and in some Hyphochytridiomycota is a phylum of "fungi" (actually classified as Protists) within the Kingdom Chromalveolata. The Labyrinthulomycetes also known as Slime nets are a group of Protists that produce a network of filaments or Tubes, which serve as tracks for Oomycetes also known as Water molds (or water moulds: see spelling differences) are a group of filamentous unicellular Heterokonts physically The opalines are a small group of peculiar Protists found as Endosymbionts in the gut of Frogs and Toads Each cell has two or more nuclei Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex [1] Most are algae, ranging from the giant multicellular kelp to the unicellular diatoms, which are a primary component of plankton. Algae ( sing. alga are a large and diverse group of simple typically Autotrophic organisms ranging from Unicellular to Multicellular forms Kelp are large Seaweeds ( Algae) belonging to the Brown algae and classified in the order Laminariales Diatoms ( Greek: (dia = "through" + (temnein = "to cut" i Plankton consist of any drifting Organisms ( Animals Plants Archaea, or Bacteria) that inhabit the Pelagic zone of Other notable members of the Stramenopila include the (generally parasitic) oomycetes, including Phytophthora of Irish potato famine infamy and Pythium which causes seed rot and damping off. Parasitism is a type of symbiotic relationship between Organisms of different Species. Oomycetes also known as Water molds (or water moulds: see spelling differences) are a group of filamentous unicellular Heterokonts physically Phytophthora (from Greek phytón “plant” and phthorá “destruction” “the plant-destroyer” is a Genus of plant-damaging Protists Pythium is a Genus of Parasitic oomycete. Because this group of organisms were once classified as Fungi, they are sometimes
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Chloroplasts
Heterokont algae are chromists with chloroplasts surrounded by four membranes, which are counted from the outermost to the innermost membrane. The Chromista are a eukaryotic supergroup probably Polyphyletic, Chloroplasts are Organelles found in Plant cells and eukaryotic Algae that conduct Photosynthesis. The first membrane is continuous with the host's chloroplast endoplasmic reticulum, or cER. The endoplasmic reticulum (Greek endo = "within" (prefix plásma = "formed entity" Latin reticulum = "little net" or ER, is an Organelle The second membrane presents a barrier between the lumen of the endoplasmic reticulum and the primary endosymbiont or chloroplast, which represents the next two membranes, within which the thylakoid membranes are found. Chloroplasts are Organelles found in Plant cells and eukaryotic Algae that conduct Photosynthesis. This arrangement of membranes suggest that heterokont chloroplasts were obtained from the reduction of a symbiotic red algal eukaryote, which had arisen by evolutionary divergence from the monophyletic primary endosymbiotic ancestor that is thought to have given rise to all eukaryotic photoautotrophs. The red algae (Rhodophyta ˌroʊdəˈfaɪtə roʊˈdɒfɨtə from Greek: ῥόδον (rhodon = rose + φυτόν (phyton = plant thus red plant are Photoautotrophs or Phototroph ( Gk: photo = light auto = self troph = nourishment are Organisms (commonly plants that carry out Photosynthesis The chloroplasts characteristically contain chlorophyll a and chlorophyll c, and usually the accessory pigment fucoxanthin, giving them a golden-brown or brownish-green color. Chlorophyll is a green Pigment found in most Plants Algae and Cyanobacteria. Fucoxanthin is a Carotenoid, with formula C42H58O6 It is found as an accessory Pigment in the Chloroplasts of
Most basal heterokonts are colorless, suggesting they diverged before aqcuisition of chloroplasts within the group. However, fucoxanthin-containing chloroplasts are also found among the haptophytes, and evidence suggests that the two groups have a common ancestry, as well as possible a common phylogenetic history with cryptomonads. The haptophytes, classed either as the Prymnesiophyta or Haptophyta are a Phylum of Algae The Chloroplasts are pigmented similarly to those of the The cryptomonads are a small group of Flagellates most of which have Chloroplasts They are common in freshwater and also occur in marine and brackish habitats In this case the ancestral heterokont was an alga, and all colorless groups arose through loss of the secondary endosymbiont and hence its chloroplast.
Motile cells
Many heterokonts are unicellular flagellates, and most others produce flagellate cells at some point in their life-cycle, for instance as gametes or zoospores. Flagellates are cells with one or more whip-like organelles called flagella. A gamete (from Ancient Greek γαμέτης; translated gamete = wife gametes = husband is a cell that fuses with another gamete A zoospore is a motile asexual Spore utilizing a Flagellum for Locomotion. The name heterokont refers to the characteristic form of these cells, which typically have two unequal flagella. The anterior or tinsel flagellum is covered with lateral bristles or mastigonemes, while the other flagellum is whiplash, smooth and usually shorter, or sometimes reduced to a basal body. The flagella are inserted subapically or laterally, and are usually supported by four microtubule roots in a distinctive pattern. Microtubules are one of the components of the Cytoskeleton. They have a diameter of 25 nm and length varying from 200 nanometers to 25 micrometers
Mastigonemes are manufactured from glycoproteins in the cell's endoplasmic reticulum before being transported to its surface. Not to be confused with Peptidoglycan. Glycoproteins are proteins that contain Oligosaccharide chains ( Glycans) covalently attached The endoplasmic reticulum (Greek endo = "within" (prefix plásma = "formed entity" Latin reticulum = "little net" or ER, is an Organelle When the tinsel flagellum moves, these create a backwards current, pulling the cell through the water or bringing in food. The mastigonemes have a peculiar tripartite structure, which may be taken as the defining characteristic of the group, thereby including a few protists that do not produce cells with the typical heterokont form. They have been lost in a few lines, most notably the diatoms.
Classification
As noted above, classification varies considerably. Originally the heterokont algae were treated as two divisions, first within the kingdom Plantae and later the Protista:
Division Chrysophyta
Class Chrysophyceae (golden algae)
Class Bacillariophyceae (diatoms)
Division Phaeophyta (brown algae)
In this scheme, however, the Chrysophyceae are paraphyletic to both other groups. The golden algae or chrysophytes are a large group of Heterokont Algae found mostly in freshwater Diatoms ( Greek: (dia = "through" + (temnein = "to cut" i The Phaeophyceae or brown algae, (singular alga is a large group of mostly marine multicellular Algae including many Seaweeds of colder In Phylogenetics, a group of organisms is said to be paraphyletic if the group contains its most recent common ancestor but does not contain all As a result, various members have been given their own classes and often divisions. Recent systems often treat these as classes within a single division, called the Heterokontophyta, Chromophyta or Ochrophyta. This is not universal, however - for instance Round et al. treat the diatoms as a division.
The discovery that oomycetes and hypochytrids are related to these algae, rather than fungi as previously thought, has led many authors to include them among the heterokonts. Oomycetes also known as Water molds (or water moulds: see spelling differences) are a group of filamentous unicellular Heterokonts physically Should it turn out that they evolved from colored ancestors, the group would be paraphyletic in their absence. Once again, however, usage varies. David J. Patterson named this extended group the stramenopiles, characterized by the presence of tripartite mastigonemes, mitochondria with tubular cristae, and open mitosis. In Cell biology, a mitochondrion (plural mitochondria) is a membrane-enclosed Organelle found in most eukaryotic cells. Cristae (singular crista) are the internal compartments formed by the inner membrane of a Mitochondrion. Mitosis is the process in which a Eukaryotic cell separates the Chromosomes in its Cell nucleus, into two identical sets in two daughter nuclei He used the stramenopiles as a prototype for a classification without Linnaean ranks. Their composition has been essentially stable, but their use within ranked systems varies.
Thomas Cavalier-Smith treats the heterokonts as identical in composition with the stramenopiles; this is the definition followed here. Professor Thomas (Tom Cavalier-Smith (born October 21 1942) FRS, FRSC, NERC Professorial Fellow is a Professor of He has proposed placing them in a separate kingdom Chromalveolata, together with the haptophytes, cryptomonads and alveolates. Chromalveolata is a Eukaryote supergroup first proposed by Thomas Cavalier-Smith as a refinement of his kingdom Chromista, which was first This is one of the most common revisions to the five-kingdom system, but has not been generally adopted, partly because some biologists doubt their monophyly. In biological Taxonomy, a kingdom or regnum is a Taxonomic rank in either (historically the highest rank or (in the new three-domain system A few treat the Chromalveolata as identical in composition with the heterokonts, or list them as a kingdom Stramenopila.
Rationale for "stramenopile"
The origin of the name stramenopile is explained by Adl and coauthors:
Regarding the spelling of stramenopile, it was originally spelled stramenopile. The Latin word for ‘‘straw’’ is stramine-us, -a, -um, adj. [stramen], made of straw—thus, it should have been spelled straminopile. However, Patterson (1989)[1] clearly stated that this is a common name (hence, lower case, not capitalized) and as a common name, it can be spelled as Patterson chooses. If he had stipulated that the name was a formal name, governed by rules of nomenclature, then his spelling would have been an orthogonal mutation and one would simply correct the spelling in subsequent publications (e. g. Straminopiles). But, it was not Patterson’s desire to use the term in a formal sense. Thus, if we use it in a formal sense, it must be formally described (and in addition, in Latin, if it is to be used botanically). However, and here is the strange part of this, many people liked the name, but wanted it to be used formally. So they capitalized the first letter, and made it Stramenopiles; others corrected the Latin spelling to Straminopiles. [2]
References
- ^ Patterson, D. J. (1999). The diversity of eukaryotes. American Naturalist 154: S96-S124
- ^ Adl, S. M. et al. (2005). "The new higher level classification of eukaryotes with emphasis on the taxonomy of protists. Journal of Eukaryotic Microbiology 52: 399-451.
Further reading
- Fletcher, R. L. 1987. Seaweeds of the British Isles. Volume 3 Fucophyceae (Phaeophyceae) Part 1. British Museum (Natural History, London. ISBN 0 565 00992 3
External links
- Tree of Life Web Project: Stramenopiles
- Penn State University: Stramenopila (also Rhodophyta, Chlorophyta)
Dictionary
heterokont
-noun
- (biology) Any alga, of the phylum Heterokontophyta, having unequal flagella
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