Aflagellate is a cell or organism with one or morewhip-likeappendages calledflagella. The wordflagellate also describes a particular construction (or level of organization) characteristic of manyprokaryotes andeukaryotes and their means of motion. The term presently does not imply any specific relationship or classification of the organisms that possess flagella. However, severalderivations of the term "flagellate" (such as "dinoflagellate" and "choanoflagellate") are more formally characterized.[1]
Flagella in eukaryotes are supported bymicrotubules in a characteristic arrangement, with nine fused pairs surrounding two central singlets. These arise from abasal body. In some flagellates, flagella direct food into acytostome or mouth, where food isingested. Flagella role in classifyingeukaryotes.
Amongprotoctists andmicroscopic animals, a flagellate is an organism with one or more flagella. Some cells in otheranimals may be flagellate, for instance thespermatozoa of most animal phyla. Flowering plants do not produce flagellate cells, butferns,mosses,green algae, and somegymnosperms and closely related plants do so.[2] Likewise, most fungi do not produce cells with flagellae, but the primitive fungalchytrids do.[3] Many protists take the form of single-celled flagellates.
Flagella are generally used forpropulsion. They may also be used to create a current that brings in food. In most such organisms, one or more flagella are located at or near the anterior of the cell (e.g.,Euglena). Often there is one directed forwards and one trailing behind. Many parasites that affect human health or economy are flagellates in at least one stage of life cycle, such asNaegleria,Trichomonas andPlasmodium.[4][5] Flagellates are the major consumers of primary and secondary production inaquatic ecosystems - consuming bacteria and other protists.[citation needed]
An overview of the occurrence of flagellated cells in eukaryote groups, as specialized cells of multicellular organisms or as life cycle stages, is given below (see also the articleflagellum):[6][7][8]
In older classifications, flagellatedprotozoa were grouped inFlagellata (=Mastigophora), sometimes divided into Phytoflagellata (= Phytomastigina, mostly autotrophic) and Zooflagellata (= Zoomastigina, heterotrophic). They were sometimes grouped withSarcodina (ameboids) in the groupSarcomastigophora.
The autotrophic flagellates were grouped similarly to the botanical schemes used for the corresponding algae groups. Thecolourless flagellates were customarily grouped in three groups, highly artificial:[11]
Protomastigineae, in which absorption of food-particles in holozoic nutrition occurs at a localised point of the cell surface, often at a cytostome, although many groups were merely saprophytes; it included the majority of colourless flagellates, and even many "apochlorotic" algae;
Pantostomatineae (or Rhizomastigineae), in which the absorption takes place at any point on the cell surface; roughly corresponds to "amoeboflagellates";
Distomatineae, a group of binucleate "double individuals" with symmetrically distributed flagella and, in many species, two symmetrical mouths; roughly corresponds to currentDiplomonadida.
Presently, these groups are known to be highlypolyphyletic. In modern classifications of the protists, the principal flagellated taxa are placed in the following eukaryote groups, which include also non-flagellated forms (where "A", "F", "P" and "S" stands for autotrophic, free-living heterotrophic, parasitic and symbiotic, respectively):[12][13]
^Raven, J.A. 2000. The flagellate condition. In: (B.S.C. Leadbeater and J.C. Green, eds)The flagellates. Unity, diversity and evolution. The Systematics Association Special Volume 59. Taylor and Francis, London. pp. 269–287.
^Webster, J & Weber, R (2007).Introduction to Fungi (3rd ed.). Cambridge: Cambridge University Press. pp. 23–24,[1]
^Tice, Alexander (2015).Understanding the evolution of aggregative multicellularity : a molecular phylogenetic study of the cellular slime mold genera sorodiplophrys and pocheina. University of Arkansas, Fayetteville.ISBN978-1-321-68823-8.OCLC985464464.
^Fritsch, F.E.The Structure and Reproduction of the Algae. Vol. I. Introduction, Chlorophyceae. Xanthophyceae, Chrysophyceae, Bacillariophyceae, Cryptophyceae, Dinophyceae, Chloromonadineae, Euglenineae, Colourless Flagellata. 1935. Cambridge, England: Cambridge University Press,[2].
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