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Heterokont Classes
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] |
Chrysophyceae
The Chrysophyceae, usually called chrysophytes, chrysomonads, golden-brown algae or golden algae are a large group of algae, found mostly in freshwater. Golden algae is also commonly used to refer to a single species, ''Prymnesium parvum'', which causes fish kills. The Chrysophyceae should not be confused with the Chrysophyta, which is a more ambiguous taxon. Although "chrysophytes" is the anglicization of "Chrysophyta", it generally refers to the Chrysophyceae. Members Originally they were taken to include all such forms of the diatoms and multicellular brown algae, but since then they have been divided into several different groups (e.g., Haptophyceae, Synurophyceae) based on pigmentation and cell structure. Some heterotrophic flagellates as the bicosoecids and choanoflagellates were sometimes seen as related to golden algae too. They are now usually restricted to a core group of closely related forms, distinguished primarily by the structure of the flagella in motile c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kelp
Kelps are large brown algae seaweeds that make up the order Laminariales. There are about 30 different genera. Despite its appearance, kelp is not a plant - it is a heterokont, a completely unrelated group of organisms. Kelp grows in "underwater forests" (kelp forests) in shallow oceans, and is thought to have appeared in the Miocene, 5 to 23 million years ago. The organisms require nutrient-rich water with temperatures between . They are known for their high growth rate—the genera ''Macrocystis'' and '' Nereocystis'' can grow as fast as half a metre a day, ultimately reaching .Thomas, D. 2002. ''Seaweeds.'' The Natural History Museum, London, p. 15. Through the 19th century, the word "kelp" was closely associated with seaweeds that could be burned to obtain soda ash (primarily sodium carbonate). The seaweeds used included species from both the orders Laminariales and Fucales. The word "kelp" was also used directly to refer to these processed ashes. Description In most kelp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ochrophyta
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 between a ... [...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 as Xant ... [...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 types ... [...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. Eukaryoti ... [...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 microscop ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pythium
''Pythium'' is a genus of parasitic oomycetes. They were formerly classified as fungi. Most species are plant parasites, but ''Pythium insidiosum'' is an important pathogen of animals, causing pythiosis. The feet of the fungus gnat are frequently a vector for their transmission. Morphology ;Hyphae: ''Pythium'' species, like others in the family Pythiaceae, are usually characterized by their production of coenocytic hyphae without septations. ;Oogonia: Generally contain a single oospore. ;Antheridia: Contain an elongated and club-shaped antheridium. Ecological importance ''Pythium''-induced root rot is a common crop disease. When the organism kills newly emerged or emerging seedlings, it is known as damping off, and is a very common problem in fields and greenhouses. Thus there is tremendous interest in genetic host resistance, but no crop has ever developed adequate resistance to ''Pythium''. This disease complex usually involves other pathogens such as ''Phytophthora'' and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Great Famine (Ireland)
The Great Famine ( ga, an Gorta Mór ), also known within Ireland as the Great Hunger or simply the Famine and outside Ireland as the Irish Potato Famine, was a period of starvation and disease in Ireland from 1845 to 1852 that constituted a historical social crisis which subsequently had a major impact on Irish society and history as a whole. With the most severely affected areas in the west and south of Ireland, where the Irish language was dominant, the period was contemporaneously known in Irish as , literally translated as "the bad life" (and loosely translated as "the hard times"). The worst year of the period was 1847, which became known as "Black '47".Éamon Ó Cuív – the impact and legacy of the Great Irish Famine During the Great Hunger, roughly 1 million people died and more than 1 million Irish diaspora, fled the country, causing the country's population to fall by 20–25% (in some towns falling as much as 67%) between 1841 and 1871.Carolan, MichaelÉireann's ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phytophthora
''Phytophthora'' (from Greek language, Greek (''phytón''), "plant" and (), "destruction"; "the plant-destroyer") is a genus of plant-damaging oomycetes (water molds), whose member species are capable of causing enormous economic losses on crops worldwide, as well as environmental degradation, environmental damage in natural ecosystems. As well as impacting large scale agriculture, ''Phytophthora'' is a nuisance to garden and indoor plant hobbyists as well as bonsai artists. The cell wall of ''Phytophthora'' is made up of cellulose. The genus was first described by Anton de Bary, Heinrich Anton de Bary in 1875. Approximately 170 species have been described, although 100–500 undiscovered ''Phytophthora'' species are estimated to exist. Pathogenicity ''Phytophthora'' species, spp. are mostly pathogens of dicotyledons, and many are relatively host-specific parasites. ''Phytophthora cinnamomi'', though, infects thousands of species ranging from club mosses, ferns, cycads, coni ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oomycete
Oomycota forms a distinct phylogenetic lineage of fungus-like eukaryotic microorganisms, called oomycetes (). They are filamentous and heterotrophic, and can reproduce both sexually and asexually. Sexual reproduction of an oospore is the result of contact between hyphae of male antheridia and female oogonia; these spores can overwinter and are known as resting spores. Asexual reproduction involves the formation of chlamydospores and sporangia, producing motile zoospores. Oomycetes occupy both saprophytic and pathogenic lifestyles, and include some of the most notorious pathogens of plants, causing devastating diseases such as late blight of potato and sudden oak death. One oomycete, the mycoparasite '' Pythium oligandrum'', is used for biocontrol, attacking plant pathogenic fungi. The oomycetes are also often referred to as water molds (or water moulds), although the water-preferring nature which led to that name is not true of most species, which are terrestrial pathogens. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parasitism
Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted structurally to this way of life. The entomologist E. O. Wilson has characterised parasites as "predators that eat prey in units of less than one". Parasites include single-celled protozoans such as the agents of malaria, sleeping sickness, and amoebic dysentery; animals such as hookworms, lice, mosquitoes, and vampire bats; fungi such as Armillaria mellea, honey fungus and the agents of ringworm; and plants such as mistletoe, dodder, and the Orobanchaceae, broomrapes. There are six major parasitic Behavioral ecology#Evolutionarily stable strategy, strategies of exploitation of animal hosts, namely parasitic castration, directly transmitted parasitism (by contact), wikt:trophic, trophicallytransmitted parasitism (by being eaten), Disease vector, vector-transmitted paras ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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