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Paramecium (/ ˌ p ær ə ˈ m iː s (i) ə m / PARR-ə-MEE-s(ee-)əm, /-s i ə m /-see-əm, plural "paramecia" only when used as a vernacular name) [2] is a genus of eukaryotic, unicellular ciliates, widespread in freshwater, brackish, and marine environments. Paramecia are often abundant in stagnant basins and ponds.
The term micronucleus may also refer to the smaller nucleus in ciliate protozoans, such as the Paramecium. In mitosis it divides by fission, and in conjugation a pair of gamete micronuclei undergo reciprocal fusion to form a zygote nucleus, which gives rise to the macronuclei and micronuclei of the individuals of the next cycle of fission. [4]
Added a label for the buccal overture, a structure frequently mislabeled as the cytostome on diagrams of Paramecium. For an accurate representation of these structures, see: Ralph Wichterman, The Biology of Paramecium, 2nd Edition, 1986 (fig. 1.3A, on... 19:47, 5 June 2017: 1,142 × 1,007 (149 KB) Deuterostome: Lengthened buccal cavity, for ...
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Paramecium are adaptive to many environments due to the diastole and systole movements of the contractile vacuole, which either let in or expel water from the cytoplasm depending on the environment. The micronucleus and macronucleus together contain all of the genetic information for the organism.
The cell cycle begins with interphase when the DNA replicates, the cell grows and prepares to enter mitosis. Mitosis includes four phases: prophase, metaphase, anaphase, and telophase. Prophase is the initial phase when spindle fibers appear that function to move the chromosomes toward opposite poles. This spindle apparatus consists of ...
Clonal aging, associated with a gradual loss of vitality, occurs in the asexual fission phase of growth of P. tetraurelia, during which cell divisions occur by mitosis rather than meiosis. In P. tetraurelia , the asexual line loses vitality and expires after about 200 fissions if the cells fail to undergo autogamy or conjugation.
The micronucleus genome contains five chromosomes that undergo mitosis during micronuclear division and meiosis during conjugation, which is the sexual division of the micronucleus. The macronuclear genome is broken down and catabolized once per life cycle during conjugation, allowing it to be site-specific, and a new macronucleus ...