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Heterokonts
Heterokonts are a group of protists (formally referred to as Heterokonta, Heterokontae or Heterokontophyta). The group is a major line of eukaryotes. Most are algae, ranging from the giant multicellular kelp to the unicellular diatoms, which are a primary component of plankton. Other notable members of the Stramenopiles include the (generally) parasitic oomycetes, including ''Phytophthora'', which caused the Great Famine of Ireland, and ''Pythium'', which causes seed rot and damping off. The name "heterokont" refers to the type of motile life cycle stage, in which the flagellated cells possess two differently arranged flagella (see zoospore). History In 1899, Alexander Luther created the term "Heterokontae" for some algae with unequal flagella, today called Xanthophyceae. Later, some authors (e.g., Copeland, 1956) included other groups in Heterokonta, expanding the name's sense. The term continues to be applied in different ways, leading to Heterokontophyta being applied a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pseudofungi
Pseudofungi is a grouping of heterokonts, also known as the Heterokontimycotina. It consists of the Oomycota and Hyphochytridiomycetes. Although numerous biochemical, ultrastructural, and genetic traits clearly place them in the heterokonts, their growth form (featuring hyphae) and mode of nutrition ( osmotrophy) resemble that of fungi (which are not closely related). Origin and ancestors It is believed that pseudofungi descend from unicellular heterokont chromist algae which lost their plastids. While evidence of these plastids hasn't been found, what has been proven is the existence of endosymbiotic red algae plastids. From this, a unicellular heterotroph proto-pseudofungi (probably a mushroom parasite) got its fungal genes through horizontal gene transfer, which would have led to the development of convergent fungal multicellularity, explaining why the cell wall is sometimes made of both chitin and cellulose Cellulose is an organic compound with the formula , a polys ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ochrophytina
The ochrophytes, subphylum Ochrophytina, is a group of mostly photosynthetic heterokonts. Their plastid is of red algal origin. The classification of the group is still being worked out. Originally, the ochrophytes were regarded as a phylum denominated Ochrophyta. Some authors (e.g., Cavalier-Smith) divided it into two subphyla, Phaeista Cavalier-Smith 1995 (comprising Hypogyristea and Chrysista in some classifications, or Limnista and Marista in others) and Khakista Cavalier-Smith, 2000 (comprising '' Bolidomonas'' and diatoms). Others prefer not to use the subphyla, listing only lower taxa (e.g., Reviers, 2002, Guiry & Guiry, 2014). However, it is currently regarded as a subphylum inside of the phylum Gyrista, along with Pseudofungi and Bigyromonada. It contains two infraphyla: Diatomista, containing diatoms and related groups, and Chrysista, containing brown and golden algae and related groups. Phylogeny The cladogram below shows the evolutionary relationships be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ochrophyta
The ochrophytes, subphylum Ochrophytina, is a group of mostly photosynthesis, photosynthetic heterokonts. Their plastid is of Red algae, red algal origin. The classification of the group is still being worked out. Originally, the ochrophytes were regarded as a phylum denominated Ochrophyta. Some authors (e.g., Thomas Cavalier-Smith, Cavalier-Smith) divided it into two subphyla, Phaeista Cavalier-Smith 1995 (comprising Hypogyristea and Chrysista in some classifications, or Limnista and Marista (alga), Marista in others) and Khakista Cavalier-Smith, 2000 (comprising ''Bolidomonas'' and diatoms). Others prefer not to use the subphyla, listing only lower taxa (e.g., Reviers, 2002, Guiry & Guiry, 2014). However, it is currently regarded as a subphylum inside of the phylum Gyrista, along with Pseudofungi and Bigyromonada. It contains two infraphyla: Diatomista, containing diatoms and related groups, and Chrysista, containing brown and golden algae and related groups. Phylogeny The c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bigyra
Bigyra is a grouping of heterokont organisms. It includes Bicosoecida, Blastocystis and Labyrinthulida. It has also been described as containing Opalozoa, Bicoecia, and Sagenista. Phylogeny The cladogram below shows the internal relationships within Bigyra: Classification The modern taxonomy of Bigyra is as follows: *Phylum Bigyra **Subphylum Opalozoa ***Infraphylum Placidozoa ****Superclass Wobblata (paraphyletic) *****Class Placididea *****Class Nanomonadea *****Class Opalomonadea ****Superclass Opalinata *****Class Opalinea *****Class Blastocystea ***Infraphylum Bikosia ****Class Bikosea **Subphylum Sagenista ***Class Labyrinthulea ***Class Eogyrea Sagenista is a group of heterokonts containing the labyrinthulids and Eogyrea, a class of yet uncultured protists. Originally, it contained the Labyrinthulids and bicosoecids. However at present the bicosoecids have been removed, and Eogyrea wer ... References External links * * SAR supergroup unranked clades [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diatom
A diatom (New Latin, Neo-Latin ''diatoma''), "a cutting through, a severance", from el, διάτομος, diátomos, "cut in half, divided equally" from el, διατέμνω, diatémno, "to cut in twain". is any member of a large group comprising several Genus, genera of algae, specifically microalgae, found in the oceans, waterways and soils of the world. Living diatoms make up a significant portion of the Earth's Biomass (ecology), biomass: they generate about 20 to 50 percent of the oxygen produced on the planet each year, take in over 6.7 billion metric tons of silicon each year from the waters in which they live, and constitute nearly half of the organic material found in the oceans. The Protist shell, shells of dead diatoms can reach as much as a half-mile (800 m) deep on the ocean floor, and the entire Amazon basin is fertilized annually by 27 million tons of diatom shell dust transported by transatlantic winds from the African Sahara, much of it from the Bodélé Dep ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protists
A protist () is any eukaryotic organism (that is, an organism whose cells contain a cell nucleus) that is not an animal, plant, or fungus. While it is likely that protists share a common ancestor (the last eukaryotic common ancestor), the exclusion of other eukaryotes means that protists do not form a natural group, or clade. Therefore, some protists may be more closely related to animals, plants, or fungi than they are to other protists. However, like the groups ''algae'', ''invertebrates'', and ''protozoans'', the biological category ''protist'' is used for convenience. Others classify any unicellular eukaryotic microorganism as a protist. The study of protists is termed protistology. History The classification of a third kingdom separate from animals and plants was first proposed by John Hogg in 1860 as the kingdom Protoctista; in 1866 Ernst Haeckel also proposed a third kingdom Protista as "the kingdom of primitive forms". Originally these also included prokaryotes, b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stramenopile
Stramenopile is a clade of organisms distinguished by the presence of stiff tripartite external hairs. In most species, the hairs are attached to flagella, in some they are attached to other areas of the cellular surface, and in some they have been secondarily lost (in which case relatedness to stramenopile ancestors is evident from other shared cytological features or from genetic similarity). Stramenopiles represent one of the three major clades in the SAR supergroup, along with Alveolata and Rhizaria. Members of the clade are referred to as 'stramenopiles'. Stramenopiles are eukaryotes; since they are neither fungi, animals, nor plants, they are classified as protists. Most stramenopiles are single-celled, but some are multicellular algae including some brown algae. The group includes a variety of algal protists, heterotrophic flagellates, opalines and closely related proteromonad flagellates (all endobionts in other organisms); the actinophryid heliozoa, and oomycetes. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sagenista
Sagenista is a group of heterokonts containing the labyrinthulids and Eogyrea, a class of yet uncultured protists. Originally, it contained the Labyrinthulids and bicosoecids. However at present the bicosoecids have been removed, and Eogyrea were added, in order to make the group monophyletic. Some have a special organelle called a bothrosome (or sagenogenetosome). It is usually found in a marine environments rich in algae and sea grass. It is capable of movement by use of this organelle. They are generally decomposers. They are cultivated for their active production of Omega-3 fatty acids. These acids are used as an approved additive for animal feed. There is a debate about whether some species of Sagenista contains a photosynthetic pigment labeled chlorophyll C. Bothrosome They are capable of excreting an extoplasmic net of filaments for cells to glide upon. These tiny filaments provide a network for cells to travel upon to soak up nutrients from the surrounding env ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Xanthophyceae
Yellow-green algae or the Xanthophyceae (xanthophytes) are an important group of heterokont algae. Most live in fresh water, but some are found in marine and soil habitats. They vary from single-celled flagellates to simple colonial and filamentous forms. Xanthophyte chloroplasts contain the photosynthetic pigments chlorophyll ''a'', chlorophyll ''c'', β-carotene, and the carotenoid diadinoxanthin. Unlike other heterokonts, their chloroplasts do not contain fucoxanthin, which accounts for their lighter colour. Their storage polysaccharide is chrysolaminarin. Xanthophyte cell walls are produced of cellulose and hemicellulose. They appear to be the closest relatives of the brown algae. Classifications The species now placed in the Xanthophyceae were formerly included in the Chlorophyceae. In 1899, Lüther created the group Heterokontae for green algae with unequal flagella. Pascher (1914) included the Heterokontae in the Chrysophyta. In 1930, Allorge renamed the group ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Flagella
A flagellum (; ) is a hairlike appendage that protrudes from certain plant and animal sperm cells, and from a wide range of microorganisms to provide motility. Many protists with flagella are termed as flagellates. A microorganism may have from one to many flagella. A gram-negative bacterium ''Helicobacter pylori'' for example uses its multiple flagella to propel itself through the mucus lining to reach the stomach epithelium, where it may cause a gastric ulcer to develop. In some bacteria the flagellum can also function as a sensory organelle, being sensitive to wetness outside the cell. Across the three domains of Bacteria, Archaea, and Eukaryota the flagellum has a different structure, protein composition, and mechanism of propulsion but shares the same function of providing motility. The Latin word means "whip" to describe its lash-like swimming motion. The flagellum in archaea is called the archaellum to note its difference from the bacterial flagellum. Eukary ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Flagellated Cells
A flagellate is a cell or organism with one or more whip-like appendages called flagella. The word ''flagellate'' also describes a particular construction (or level of organization) characteristic of many prokaryotes and eukaryotes and their means of motion. The term presently does not imply any specific relationship or classification of the organisms that possess flagella. However, the term "flagellate" is included in other terms (such as "dinoflagellate" and " choanoflagellata") which are more formally characterized. Form and behavior Flagella in eukaryotes are supported by microtubules in a characteristic arrangement, with nine fused pairs surrounding two central singlets. These arise from a basal body. In some flagellates, flagella direct food into a cytostome or mouth, where food is ingested. Flagella often support hairs, called mastigonemes, or contain rods. Their ultrastructure plays an important role in classifying eukaryotes. Among protoctists and microscopi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zoospore
A zoospore is a motile asexual spore that uses a flagellum for locomotion. Also called a swarm spore, these spores are created by some protists, bacteria, and fungi to propagate themselves. Diversity Flagella types Zoospores may possess one or more distinct types of flagella - tinsel or "decorated", and whiplash, in various combinations. *Tinsellated (straminipilous) flagella have lateral filaments known as mastigonemes perpendicular to their main axis, which allow for more surface area, and disturbance of the medium, giving them the property of a rudder, that is, used for steering. *Whiplash flagella are straight, to power the zoospore through its medium. Also, the "default" zoospore only has the propelling, whiplash flagella. Both tinsel and whiplash flagella beat in a sinusoidal wave pattern, but when both are present, the tinsel beats in the opposite direction of the whiplash, to give two axes of control of motility. Morphological types In eukaryotes, the four main type ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
