Definitions

amoeba

amoeba

[uh-mee-buh]
amoeba: see ameba.

Amoeba (magnified).

One-celled protozoan that can form temporary extensions of cytoplasm (pseudopodia) in order to move about. Some amoebas are found on the bottom of freshwater streams and ponds. Others live in the human digestive system; one type causes amebic dysentery in humans. Each amoeba contains a small mass of jellylike cytoplasm with vacuoles and a nucleus. Food is taken in and material is excreted at any point on the cell surface. Amoebas are used extensively in cell research for determining the relative functions and interactions of the nucleus and the cytoplasm.

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Chaos is a genus of giant amoebae, varying from 1-5 mm in length. They are closely related to Amoeba, and share the same general morphology, producing numerous cylindrical pseudopods. However, Chaos have several hundred nuclei, while Amoeba only have one. The most notable species is C. carolinensis; they have also been classified as Pelomyxa, another giant multinucleate amoeba, but they are not particularly similar.

Chaos feed on bacteria, fungi, other protists and multicellular rotifers. They are heterotrophs like all members of sarcodina, and obtain food energy by ingestion. They are mostly scavengers and are found on the bottom of freshwater habitats.

Chaos move by pseudopodia. They do not have a hard cell wall. The cytoplasm is divided into the endoplasm which is fluid and contains the many nuclei, granules, and food vacuoles, and the ectoplasm which is more viscous and does not contain any granules.

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