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Ciliophora (sĬl´ē-ŏf´ərə), phylum in the kingdom Protista consisting of the ciliates, or ciliophores, complex freshwater or saltwater protozoans that swim by the coordinated beating of their cilia—short, hairlike structures that cover the cell surface. Like other protozoans, ciliates are unicellular heterotrophs. Some feed on bacteria and other particles as well as algae by means of cilia-created currents; many are carnivorous. In some species the cilia are organized into rows or clumps that the organisms use to walk or jump. Ciliates contain a variety of organelles plus two kinds of nuclei. The larger type of nucleus, the macronucleus, contains a great deal more DNA than the smaller nucleus, the micronucleus. Although the ciliates typically reproduce asexually, they also exchange genetic information with other ciliate cells by the process of conjugation. During this process two cells unite, the micronuclei undergo meiosis, then pair up and fuse with similar haploid micronuclei from the other organism, mixing the DNA from the two organisms.

There are approximately 8,000 species of ciliates. The phylum includes the slipper-shaped paramecium and the trumpet-shaped stentor. The suctorians are sessile ciliates that suck out the protoplasm of their prey through tentacles.

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Ciliophora (phylum Protozoa) A subphylum of protozoa in which cilia are present during at least one stage of the life cycle and in which two different types of nucleus (macronucleus and micronucleus) are normally present. Cells reproduce by binary fission. Sexual processes occur. Most species are free-living, although some are parasitic. There is one class, Ciliatea, containing four subclasses, many orders, and numerous genera.

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Ciliophora A phylum of the Protoctista containing ciliated protozoa – ciliates – (including Paramecium) that possess two types of nuclei, a micronucleus and macronucleus (see nucleus). The cilia are used for feeding and locomotion. Ciliates reproduce sexually by conjugation.