Amoeba
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2008-07-17T01:46:12Z
Ukexpat
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Reverted edits by [[Special:Contributions/60.241.82.45|60.241.82.45]] to last version by 213.16.241.12 (using [[WP:HG|Huggle]])
{{otheruses}}
{{Taxobox|
| name = ''Amoeba''
| color = khaki
| image = Chaos diffluens.jpg
| image_width = 250px
| domain = [[Eukaryota]]
| kingdom = [[Protista]]
| class = Rhizopoda
| order = [[Amoebida]]
| familia = Amoebidae
| genus = '''''Amoeba'''''
| genus_authority = [[Bory de Saint-Vincent]], 1822
| subdivision_ranks = Species
| subdivision =
''[[Amoeba proteus]]''<br>
''[[Amoeba dubia]]''
{{Expand-section|date=June 2008}}
}}
'''''Amoeba''''' (sometimes '''''amœba''''' or '''''ameba''''', plural '''''amoebae''''') is a [[genus]] of [[protozoa]] that moves by means of [[pseudopod]]s, and is well-known as a representative [[Microorganism|unicellular organism]]. The word '''amoeba''' or '''ameba''' is variously used to refer to it and its close relatives, now grouped as the [[Amoebozoa]], or to all protozoa that move using pseudopods, otherwise termed [[amoeboid]]s.
==History==
The amoeba was first discovered by [[August Johann Rösel von Rosenhof]] in 1755.<ref>{{cite journal | last = Leidy | first = Joseph | title = Amoeba proteus | journal = The American Naturalist | volume = 12 | issue = 4 | year = 1878 | pages = 235–238 | url = http://links.jstor.org/sici?sici=0003-0147%28187804%2912%3A4%3C235%3AAP%3E2.0.CO%3B2-7 | accessdate = 2007-06-20 | doi = 10.1086/272082}}</ref> Early naturalists referred to ''Amoeba'' as the ''Proteus animalcule'' after the [[Greek mythology|Greek]] god [[Proteus]] who could change his shape. The name "amibe" was given to it by [[Bory de Saint-Vincent]]<ref>http://books.google.com/books?id=1I8DAAAAQAAJ&pg=PA158&lpg=PA158&dq=%22bory+de+saint+vincent+jean+baptiste+genevieve+marcellin%22+amibe&source=web&ots=SCcqmYPPSy&sig=vje4JuVmdQzWrFqpXTw2UjRsgx8#PPA5,M1</ref>, from the Greek ''amoibè'', meaning change.<ref name = EOS1>{{cite book | first = Kimberley | last = McGrath | coauthors = Blachford, Stacey (eds.) | title = Gale Encyclopedia of Science Vol. 1: Aardvark-Catalyst (2nd ed.) | year = 2001 | isbn = 078764370X | publisher = Gale Group}}</ref>
==Habitat and uses==
''Amoeba'' itself is found in decaying [[vegetation]], in [[Fresh water|fresh]] and [[Saline water|salt]] water, wet soil, and animals.<ref name = EOS1/> Due to the ease with which they may be obtained and kept alive, they are common objects of study as representative protozoa and to demonstrate cell structure and function.
==Anatomy==
[[Image:Amoeba (PSF).png|thumb|250px|Anatomy of an amoeba]]
The cell's [[organelle]]s and [[cytoplasm]] are enclosed by a [[cell membrane]], obtaining its food through [[phagocytosis]]. Amoebae have a single large tubular [[pseudopod]] at the [[Anatomical terms of location|anterior]] end, and several secondary ones branching to the sides. The most famous species, ''[[Amoeba proteus]]'', is 700-800 [[Micrometre|μm]] in length but the species ''[[Amoeba dubia]]'' is as large as a millimeter, and visible to the naked eye. Some ameobas have an appendage designed specifically for the phagocytosis of silicone{{Fact|date=May 2008}} . Its most recognizable features include one or more [[cell nuclei|nuclei]] and a simple contractile [[vacuole]] to maintain [[osmosis|osmotic equilibrium]]. Food enveloped by the amoeba is stored and digested in vacuoles. Amoebae reproduce via [[binary fission]]. In cases where the amoeba are forcibly divided, the portion that retains the nucleus will survive and form a new cell and cytoplasm, while the other portion dies. Amoebas also have no definite shape.<ref name = SC>{{cite web | url = http://www.scienceclarified.com/Al-As/Amoeba.html | language = english | format = html | publisher = Scienceclarified.com | title = Amoeba |
== Reaction to stimuli ==
=== Hypertonic and hypotonic solutions ===
Like most cells, amoebae are adversely affected by excessive [[Osmosis|osmotic pressure]] caused by extremely saline or dilute water. Amoebae will prevent the influx of salt in saline water, resulting in a net loss of water as the cell becomes [[isotonic]] with the environment, causing the cell to shrink. Placed into [[fresh water]], amoebae will also attempt to match the concentration of the surrounding water, causing the cell to swell and sometimes burst.<ref name=Patterson1981>{{cite journal | author = Patterson, D.J. | year = 1981 | title = Contractile vacuole complex behaviour as a diagnostic character for free living amoebae | journal = Protistologica | volume = 17 | pages = 243–248}}</ref> Adjusting the tonicity of the cytoplasm can also damage the digestive enzymes used in phagocytosis, allowing the amoeba to ingest food but not extract energy, resulting in death.<ref name = EOS1/>
=== Amoebic cysts ===
{{main|Microbial cyst}}
In environments which are potentially lethal to the cell, an amoeba may become dormant by forming itself into a ball and secreting a protective membrane to become a [[microbial cyst]]. The cell remains in this state until it encounters more favourable conditions.<ref name = SC/> While in cyst form the amoeba will not replicate and may die if unable to emerge for a lengthy period of time.
=== Marine amoeba ===
Marine amoeba lack contractile vacuoles and their [[enzyme]]s and organelles are not damaged by the salt water found in seas, oceans, salt swamps, salty rivers and ponds.
==In popular culture==
{{Trivia|date=July 2008}}
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*[[Tom Robbins]] states in the [[preface]] to his 1976 novel ''[[Even Cowgirls Get the Blues]]'' that amoebas are [[Cool (aesthetic)|cool]] because they [[reproduce]] by [[binary fission]], so the first amoeba is still alive to this day. The first sentence of the book is "Amoebae have no fossils."
* In the 1984 computer game [[Boulder Dash]], Rockford, the main character, interacts frequently with a constantly-growing green amoeba.
* The contemporary British Poet, [[John Hegley]], has a poem entitled ''Amoeba''.
* [[The Adolescents]] have a song titled "Amoeba"
* [[The Powerpuff Girls]] and [[Demashita! Powerpuff Girls Z]] have a trio of villains called The Amoeba Boys, who are shown to be lacking in their capacity for true villainous activity (as in one episode, where they steal an orange from a street vendor, and then give it back) compared with world-domination-centered villains such as Mojo Jojo. This seems to be explained by their lack of brain (being single-celled organisms).
* The 48th produced episode of the classic [[Star Trek: The Original Series|Star Trek]] series ([[The Immunity Syndrome (TOS episode)|The Immunity Syndrome]]) featured an 11,000-mile (~17 700 km) wide amoeba threatening not only the life of Captain Kirk and his crew, but all life throughout the galaxy.
* In the fourth installment of [[The Legend of Zelda]] ([[Ocarina of Time]]), the dungeon boss of the Water Temple is a giant Amoeba that fuses with the water around it.
* Jon Scieszka's book, ''[[Science Verse]]'', had a poem called ''Amoeba where are you aneba"
* In the second epidode of [[Futurama]], Bender says to Fry that he hasn't "touched his amoeba" in a sushi like restaurant. The amoeba is depicted as a large, green, jelly-like blob.
==References==
{{Reflist}}
==External links==
* [http://tolweb.org/notes/?note_id=51 Amoebae: Protists Which Move and Feed Using Pseudopodia, David Patterson (Tree of Life)]
* [http://wikibooks.org/wiki/Biology_Cell_biology_Introduction_Cell_size Wikibooks: compare size of cells]
* [http://www.bairbrepaws.com/psneeley/FwrPLA.htm Joseph Leidy's Amoeba Plates]
[[Category:Protista]]
[[Category:Amoeboids]]
[[Category:Amoebozoa]]
[[ar:أميبا (كائن دقيق)]]
[[bs:Amebe]]
[[bg:Амеба]]
[[da:Amøbe]]
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[[el:Αμοιβάδα]]
[[et:Amööb]]
[[es:Ameba]]
[[fr:Amibe]]
[[ko:아메바]]
[[hi:अमीबा]]
[[it:Amoeba]]
[[he:אמבה]]
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[[nl:Amoebe]]
[[ja:アメーバ]]
[[no:Amøbe]]
[[nn:Amøbe]]
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[[sr:Амеба]]
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[[uk:Амеба]]
[[zh:變形蟲]]