| Fibrillar surface coat
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Fibrous component covering the entire surface of the flagellum/cilium. Chlamydomonas and Chlamydobotrys have flagella/cilia bearing a fibrillar surface coat. Synonyms: tomentum. [Link to this definition]
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| Fibrous roots
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Roots composed of a bundle of filaments, the thickness of which varies in roots of different origins. Frequently, but not always, the bundles appear cross-striated. It is probable that the first types of flagellar or ciliary roots seen by light microscopy were fibrous roots. These roots have turned out to be structurally and chemically heterogenous in comparison to micro-tubular roots. In addition, cell and molecular biology studies may be necessary to determine their type by assessment of contractility, ion-binding characteristics, and ATPase activity as well as characterizing their proteins by antibody-binding tests. In some cells the fibrous roots remain superficial (near the plasma membrane) throughout their length; the ciliate "kinetodesmal fibers", the superficial "transverse striated fibre" of some dinoflagellates or the "costa" of trichomonads are of this type. In other cells the striated roots extend deep into the cell cytoplasm, like the "rhizoplast" of many flagellates or the "para-basal fibers" of many metamonads, where they may make contact with such organelles as the nucleus, Golgi apparatus, plastid or mitochondrion. Centrin, assemblin, and giardin may represent common types of proteins that are formed into fibrous roots with distinctive properties. It is clear that exciting discoveries are being made in studies on the fibrous roots of protists, but our knowledge is very elementary at present. At this time there is not enough knowledge to classify all fibrous roots in the various protists into clear-cut categories, and this must await further biochemical characterization. At present, only two different types of fibrous roots, which occur in green algae, have been characterized biochemically in detail; these are System I and System II fibers. Synonyms: rhizoplast. [Link to this definition]
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| FIELD OF VIEW
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The area that may be seen when looking down the eyepieces of a microscope. The width depends on the design of the microscope and the choice of objective, but is always the same for a given objective and so can be exploited to make rough estimates of cell size [Link to this definition]
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| FILAMENT
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A thin strand, may refer to the appearance of an organism, a strand of cytoplasm, or to the strand of metal wire in a bulb which is heated to give off light. [Link to this definition]
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| FILAMENTOUS GREEN ALGAE
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A type of green algae (see green algae) in which the cells are joined end to end to form filaments. Aggregates may form a kind of green cotton wool or even bigger aggregates in (usually) freshwater habitats. [Link to this definition]
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| FILOSE
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Refers to a type of thin, thread-like pseudopodium without internal skeleton (Fig. **). [Link to this definition]
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| FILTER FEEDER
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A type of feeding in which suspended particles are consumed: [Link to this definition]
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| FIX
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To attach (for example to the substrate); or to kill and preserve. [Link to this definition]
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| Flagellar apparatus/kinetid
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An organellar complex consisting of one or more basal bodies/kinetosomes that may bear flagella/ cilia, may have microtubular and fibrous roots associated with their bases, and may function in locomotion, feeding, sensation, and reproduction. There is tremendous diversity in the elements that make up the flagellar apparatus/kinetid; some elements are homologs and some are analogs. Comparisons of the flagellar apparatus/kinetid of seemingly very different taxa have suggested the existence of new monophyletic assemblages. [Link to this definition]
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| FLAGELLAR HAIRS
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The stramenopiles (= heterokonts) and a few other algae are characterised by having stiff hairs on the flagella. Filamentous appendages usually arranged in one or more rows but not covering the entire surface of a flagellum/cilium. These have the effect of reversing the direction that water flows, so as waves pass along the flagella from base to tip, so food is drawn from the tip towards the organism where it can be ingested.Flagellar hairs of protists were first described in the 19th century using Loeffler's staining method for bacterial flagella. These hairy flagella were termed "Flimmergeisseln". Later, the term "mastigoneme" was introduced. Today, several very distinct types of flagellar hairs have been described. Synonyms: flimmer, mastigoneme, tinsel. [Link to this definition]
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| FLAGELLAR MEMBRANE
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The membrane enclosing the axonemal part of a eukaryotic flagellum. [Link to this definition]
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| FLAGELLAR POCKET
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A depression in the cell surface of euglenids and cryptomonads at the base of which are inserted the flagella. May be referred to as a reservoir. [Link to this definition]
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| Flagellar scales
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Organic structures of discrete size and shape, often covering the whole surface of the flagellum/cilium and generally assembled in the Golgi apparatus. Flagellar scales usually differ in structure from scales present on the cell body proper. Different scale types are usually distinguished by descriptive terms like basket scales, canistrate scales, dendritic scales, flowerpot scales, knotted scales, limulus scales, man scales, pentagonal scales, spider-web scales, square-shaped scales, tree scales. [Link to this definition]
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| Flagellar/ciliary matrix
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The cytosol of the flagellum/cilium, often lacking structural detail. [Link to this definition]
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| Flagellar/ciliary membrane
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The extension of the plasma membrane that encloses the axoneme and flagellar/ciliary matrix. [Link to this definition]
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| Flagellar/ciliary roots
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Fibrous, microtubular or amorphous structures originating at or near basal bodies/kinetosomes and terminating somewhere else in the cell but not at nearby basal bodies/kinetosomes. The two major types are fibrous roots and microtubular roots. Synonyms: flagellar rootlets. [Link to this definition]
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| Flagellar/ciliary surface
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Structures associated with the outer surface of the flagellar/ciliary membrane, including fibrillar surface coat, hairs and scales. [Link to this definition]
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| FLAGELLATE
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A kind of protist bearing flagella; a very diverse group with unclear boundaries. Distinguished from ciliates because flagella are few in number, and usually create a thrust along the length of the organelle rather than parallel to the body surface. [Link to this definition]
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| FLAGELLUM
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Filamentous structures used for motion. Flagella of prokaryotes are biochemically, structurally, and functionally very different to flagella of eukaryotes. The eukaryotic flagellum has a skeletal component comprised of microtubules and is flexed by an interaction of the protein dynein with microtubules. The microtubules form a cylindrical structure - the axoneme - inside the flagellum. Cilia are a modified kind of eukaryotic flagellum. Prokaryotes have a stiff flagellum that is rotated to propel the cell. Plural flagella. See bacterial flagella and eukaryotic flagella [Link to this definition]
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| Flagellum/ Cilium
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A long, cylindrical extension of a eukaryotic cell, bounded by the plasma membrane and containing an axoneme. A flagellum/cilium is a motility organelle that is mainly involved in cell movement by means of water propulsion, but can perform additional functions such as feeding, mating, and sensory perception. The flagellum/cilium can be subdivided into different sub-compartments: (1) axoneme, (2) paraxonemal structures, (3) flagellar/ciliary matrix, (4) flagellar/ciliary membrane, (5) flagellar/ciliary surface. In the axial direction each sub-compartment of the flagellum/cilium can often be subdivided into 3 parts: tip, shaft, and transitional region/zone. Synonyms: eukaryotic flagellum, undulipodium [Link to this definition]
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| FLATWORM
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A type of metazoan (p. **) using cilia and muscles for movement and ingesting food through a muscular channel, the pharynx. Soft bodied. [Link to this definition]
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| FLOTATION
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Pertaining to floating, protists may modified to favour floating rather than sinking, and typical adaptations to floatation include long arms or spines. [Link to this definition]
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| FLUORESCENCE
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Fluorescence microscopy relies on irradiating a sample with a relatively high energy beam of light, and then looking at the specimen through a filter that blocks the original illumination. This may reveal that some parts of a cell have absorbed some of the incident light and then release some of the energy as radiation with lower energy (longer wavelength). Typically, blue or ultraviolet light is used to irradiate the specimen, and the fluorescence involves a shift to the red end of the spectrum. This image shows a diatom using phase contrast microscopy and fluorescence microscopy, in the latter case we only see the chloroplast emitting red light. [Link to this definition]
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| FOCAL PLANE
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A plane in which the image produced by a microscope is in focus. Used, for example, in reference to the location of the image or of the shutter of a camera. [Link to this definition]
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| FOOD WEB
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A ecological concept conveying a sense of the complex interactions within a community, where organisms can indirectly or directly affect others by acting as food, acting as predators, or in competing with each other for food. [Link to this definition]
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| FREE-LIVING
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As opposed to parasitic or symbiotic, referring to organisms that live in inert habitats (water bodies, soils, sands, etc), and move and gain their food without relying on the intervention of other species. The category does not have sharp boundaries. [Link to this definition]
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| FREE-SWIMMING
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Indicating that an organism is able to move freely through the fluid phase of medium. Compare with crawling or gliding where the organism requires contact with the substrate [Link to this definition]
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| FRONT
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The anterior, the part of the cell projecting forwards when it is moving [Link to this definition]
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| Frustule
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All siliceous components of the vegetative cell wall of diatoms, comprising two valves, the epivalve and hypovalve, and the girdle (or cingulum). Usually with detailed sculptings that are used in taxonomy. The epivalve plus epicingulum comprises the epitheca, which is that component of the frustule inherited from the parent cell during division. The hypovalve plus hypocingulum constitutes the hypotheca, or that component of the frustule deposited by daughter cells following division. The frustule plus any additional organic component(s) (see Diatotepum), regardless of the composition, are together referred to as the diatom cell wall. It has been reported that silicification of the frustule may occur on an organic matrix (template?), though this has not been conclusively demonstrated. Frustule components, particularly the valves, are normally adorned with a vast range of morphological features defined by an equally vast and precise terminology. See also, Auxospore wall. [Link to this definition]
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| Fultoportula
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Plural: fultoportulae. Hollow tubular process in the valve of centric diatoms, through which polysaccharides and other carbon-containing substances are extruded. Characterized by the absence of a lip-shaped internal aperture (see rimoportula) and by the presence of buttresses or struts at the base of either the internal or external aperture, or both. Synonym: strutted process. Occurrence, distribution, and detailed structure of fultoportulae are among the characters used to characterize diatom genera and species. Image by Charley O'Kelly. [Link to this definition]
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| Fuzzy coat
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see
Glycocalyx.[Link to this definition]
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