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Sarcodina, the largest phylum (11,500 living species and 33,000 fossil species) of protozoans). It comprises the amebas and related organisms; which are all solitary cells that move and capture food by means of pseudopods, flowing temporary extensions of the cell. Most sarcodines are free living; others are parasitic. One of these parasites is the causative organism of amebic dysentery. With the exception of chloroplasts, sarcodines are identical to the ameboid members of the phylum Chrysophyta. Sarcodines may reproduce asexually by cell division, often without breakdown of the nuclear envelope that is typical in mitosis, or sexually by meiosis and the production of haploid gametes, followed by fusion of gametes and the formation of zygotes.

The sarcodines include the naked forms (amebas) and forms with perforated shells, or tests, through which pseudopods may be extended. Best known of the shelled forms are the foraminiferans, with calcium carbonate shells.

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Sarcodina (phylum Protozoa, subphylum Sarcomastigophora) A superclass of protozoa which form pseudopodia for feeding and locomotion. There are three classes, and many orders. The majority of species live in marine aquatic environments but some occur in fresh water (and are important members of the soil fauna) and some are parasitic in the intestinal tracts of vertebrates and invertebrates. The superclass includes the Radiolaria, known from the Cambrian, and the Heliozoa, which are exclusively freshwater and have a fossil record that extends back only to the Pleistocene.