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Amoeboids are cells that move or feed by means of temporary projections, called pseudopods (false feet). They have appeared in a number of different groups. Some cells in multicellular animals may be amoeboid, for instance human white blood cells, which consume pathogens. Many protists exist as individual amoeboid cells, or take such a form at some point in their life-cycle. The most famous such organism is Amoeba proteus; the name amoeba is variously used to describe its close relatives, other organisms similar to it, or the amoeboids in general.
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Amoeboids may be divided into several morphological categories based on the form and structure of the pseudopods. Those where the pseudopods are supported by regular arrays of microtubules are called actinopods, and forms where they are not are called rhizopods, further divided into lobose, filose, and reticulose amoebae. There is also a strange group of giant marine amoeboids, the xenophyophores, that do not fall into any of these categories.
Traditionally the amoeboid protozoa are grouped together as the Sarcodina, variously ranked from class to phylum, with each of the above categories as a formal subtaxon. However, since they are all based on form rather than phylogeny, newer systems generally separate some out or abandon them entirely. Most amoeboids are now included in two major supergroups - the Amoebozoa, including most lobose amoebae and slime moulds, and the Rhizaria, including the Cercozoa, Foraminifera, radiolarian classes and certain heliozoa. However, amoeboids have appeared separately in many other groups, including various different lines of algae not listed above.
Amoeboids are classified in a sub-phylum called sarcodina. Basically, amoeboids move by moving their cytoplasm, resembling limbs, to move around and engulf food particles with its cytoplasm. Some amoeba may form a glass covering around and over its normal amoeba body. When these protozoan die, their glass stays intact as the cytoplasm gradually dies. These glass particles then accumulate and are use to make many products, such as the luminosity of road paint, or the grit in toothpaste. Amoeboids mainly consist of contractile vacuoles, a nucleus, and cytoplasm as their basic structure. As the cytoplasm surrounds the prey, it injects enzymes into the organism, thus digesting their prey.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Amoeboid". A list of authors is available in Wikipedia.|