Paramecium

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Paramecium
Paramecium aurelia
Scientific classification
Domain:	Eukarya
Kingdom:	Protista
Phylum:	Ciliophora
Class:	Ciliatea
Order:	Peniculida
Family:	Parameciidae
Genus:	Paramecium Müller, 1773
Species
Paramecium aurelia Paramecium bursaria Paramecium caudatum Paramecium tetraurelia

Paramecium is a group of unicellular ciliate protozoa, which are commonly studied as a representative of the ciliate group, and range from about 50 to 350 μm in length. Simple cilia cover the body, which allow the cell to move with a synchronous motion (like a caterpillar) at speeds of approximately 2,700μm/second (12 body lengths per second). There is also a deep oral groove containing inconspicuous tongue-like compound oral cilia (as found in other peniculids) used to draw food inside. They generally feed on bacteria and other small cells, making them heterotrophs. Osmoregulation is carried out by a pair of contractile vacuoles, which actively expel water from the cell absorbed by osmosis from their surroundings. They are relatively large protists and can easily be seen with a medium-power microscope.
Paramecia are widespread in freshwater environments, and are especially common in scums. Recently, some new species of Paramecia have been discovered in the oceans.
Certain single-celled eukaryotes, such as Paramecium, are examples for exceptions to the universality of the genetic code: in their translation systems a few codons differ from the standard ones.

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