Difference between revisions of "Amoeba" - New World Encyclopedia
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{{Taxobox_begin | name = ''Amoeba'' | color = khaki}} | {{Taxobox_begin | name = ''Amoeba'' | color = khaki}} | ||
{{Taxobox_image | image = [[Image:Chaos diffluens.jpg|240px|Chaos diffluens]] | caption = ''[[Amoeba proteus]]''}} | {{Taxobox_image | image = [[Image:Chaos diffluens.jpg|240px|Chaos diffluens]] | caption = ''[[Amoeba proteus]]''}} | ||
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| − | + | '''''Amoeba''''' (also spelled ''ameba'') is a genus of [[protozoa]] that moves by means of temporary projections called [[pseudopods]] (false feet), and is well-known as a representative unicellular organism. Protozoa are single-celled eukaryotes, which demonstrate mobility and heterotrophy like animals, but are grouped in the kingdom Protista. The plural of amoeba is spelled either amoebas or amoebae. | |
| − | + | The word amoeba is also used to refer to both this genus and its close relatives, now grouped as the "Amoebozoa," and to refer to all unicellular organisms that move by pseudopods. The pseudopods, or "false feet", result from the extending of cytoplasm outward. Any cells that move or feed by such temporary projects are referred to as amoeboid, and even some cells in multicellular organisms are amoeboid, such as human white blood cells that consume pathogens. | |
| − | + | Unification Aspects | |
Early naturalists referred to ''Amoeba'' as the [[Proteus]] [[animalcule]], after a Greek god who could change his shape. The name "amibe" was given to it by Bery St. Vincent, from the Greek ''amoibe'', meaning change. | Early naturalists referred to ''Amoeba'' as the [[Proteus]] [[animalcule]], after a Greek god who could change his shape. The name "amibe" was given to it by Bery St. Vincent, from the Greek ''amoibe'', meaning change. | ||
| − | + | ==Characteristics== | |
| + | ''Amoeba'' itself is found in freshwater, typically on decaying vegetation from streams, but is not especially common in nature. However, because of the ease with which they may be obtained and kept in the lab, they are common objects of study, both as representative protozoa and to demonstrate cell structure and function. The cells have several lobose pseudopods, with one large tubular pseudopod at the anterior and several secondary ones branching to the sides. | ||
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| + | The most famous amoeba species, ''A. proteus'', is 700-800 μm in length, but many others are much smaller. Each has a single [[cell nucleus|nucleus]], and a simple contractile [[vacuole]] which maintains its [[osmosis|osmotic]] pressure, as its most recognizable features. | ||
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| + | Amoebas reproduce by splitting into two parts (binary fission). For this reason, writer Tom Robbins states, in the preface to his book ''Even Cowgirls Get the Blues'', that amoebas are [[cool]] because they reproduce by binary fission, so the first amoeba is still alive to this day. | ||
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| + | ==Amoeba and human disease== | ||
| − | + | [[Image:Lifecycle_entamoebahistolytica.gif|thumb|300px|Life Cycle of ''Entamoeba histolytica'']] | |
| + | There are at least six species of amoeba, in the broader sense of amoebozoa, that are parasitic in humans. However, most of these are classified as "nonpathogenic intestinal amoeba infection." That means that these parasites are categorized as never making people sick or harm the body, even in people with weak immune systems. For example, ''Entamoeba coli'', ''Entamoeba dispar'', and ''Entamoeba hartmanni'' are considered harmless parasites. | ||
| − | + | ''Entamoeba histolytica'', however, is a parasitic amoeba that causes harm to humans. Amebiasis is the disease caused by infection with this amoebozoa. It is most common in developing countries that have poor sanitary conditions. Mild amebiasis is associated with stomach pain and stomach cramping, but a severe form is amebic dysentery, which results with stomach pain, fever, and bloody stools. In the worse (but rare) case it can spread to other parts of the body, including the brain and lungs. As a protection, one is advised to drink only bottled or boiled water, verus drinking from fountain drinks, or taking any drinks with ice cubes. (Thus, the line in Sammy Hager's song Mas Tequilla set in Mexico: "You can drink the water, but don't eat the ice.") One is also advised not to eat fresh fruit or vegetables that you did not personally peel, or non pasteurized dairy products. | |
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| − | + | ==Collection== | |
| + | A good method of collecting amoeba is to lower a jar or upside down until it is just above the sediment surface. Then slowly let air escape so the top layer will be sucked into the jar. Try not to allow deeper sediment get sucked in. You can slowly move the jar when tilting it so you collect from a larger area. If no amoeba are found, one can try introducing some rice grains into the jar and waiting for them to start to rot. The bacteria eating the rice will be eaten by the amoeba, thus increasing the population and making them easier to find. | ||
==External links== | ==External links== | ||
Revision as of 02:36, 5 February 2006
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Amoeba (also spelled ameba) is a genus of protozoa that moves by means of temporary projections called pseudopods (false feet), and is well-known as a representative unicellular organism. Protozoa are single-celled eukaryotes, which demonstrate mobility and heterotrophy like animals, but are grouped in the kingdom Protista. The plural of amoeba is spelled either amoebas or amoebae.
The word amoeba is also used to refer to both this genus and its close relatives, now grouped as the "Amoebozoa," and to refer to all unicellular organisms that move by pseudopods. The pseudopods, or "false feet", result from the extending of cytoplasm outward. Any cells that move or feed by such temporary projects are referred to as amoeboid, and even some cells in multicellular organisms are amoeboid, such as human white blood cells that consume pathogens.
Unification Aspects
Early naturalists referred to Amoeba as the Proteus animalcule, after a Greek god who could change his shape. The name "amibe" was given to it by Bery St. Vincent, from the Greek amoibe, meaning change.
Characteristics
Amoeba itself is found in freshwater, typically on decaying vegetation from streams, but is not especially common in nature. However, because of the ease with which they may be obtained and kept in the lab, they are common objects of study, both as representative protozoa and to demonstrate cell structure and function. The cells have several lobose pseudopods, with one large tubular pseudopod at the anterior and several secondary ones branching to the sides.
The most famous amoeba species, A. proteus, is 700-800 μm in length, but many others are much smaller. Each has a single nucleus, and a simple contractile vacuole which maintains its osmotic pressure, as its most recognizable features.
Amoebas reproduce by splitting into two parts (binary fission). For this reason, writer Tom Robbins states, in the preface to his book Even Cowgirls Get the Blues, that amoebas are cool because they reproduce by binary fission, so the first amoeba is still alive to this day.
Amoeba and human disease
There are at least six species of amoeba, in the broader sense of amoebozoa, that are parasitic in humans. However, most of these are classified as "nonpathogenic intestinal amoeba infection." That means that these parasites are categorized as never making people sick or harm the body, even in people with weak immune systems. For example, Entamoeba coli, Entamoeba dispar, and Entamoeba hartmanni are considered harmless parasites.
Entamoeba histolytica, however, is a parasitic amoeba that causes harm to humans. Amebiasis is the disease caused by infection with this amoebozoa. It is most common in developing countries that have poor sanitary conditions. Mild amebiasis is associated with stomach pain and stomach cramping, but a severe form is amebic dysentery, which results with stomach pain, fever, and bloody stools. In the worse (but rare) case it can spread to other parts of the body, including the brain and lungs. As a protection, one is advised to drink only bottled or boiled water, verus drinking from fountain drinks, or taking any drinks with ice cubes. (Thus, the line in Sammy Hager's song Mas Tequilla set in Mexico: "You can drink the water, but don't eat the ice.") One is also advised not to eat fresh fruit or vegetables that you did not personally peel, or non pasteurized dairy products.
Collection
A good method of collecting amoeba is to lower a jar or upside down until it is just above the sediment surface. Then slowly let air escape so the top layer will be sucked into the jar. Try not to allow deeper sediment get sucked in. You can slowly move the jar when tilting it so you collect from a larger area. If no amoeba are found, one can try introducing some rice grains into the jar and waiting for them to start to rot. The bacteria eating the rice will be eaten by the amoeba, thus increasing the population and making them easier to find.
External links
Credits
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