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Lower plants Algae and mushrooms [#] Navigation Main Virus Department drobyanka Algae Slizeviki Mushrooms Lichens Friends Recommend Drobyanka DEPARTMENT drobyanki (SCHIZOPHYTA) Its name drobyanki have received for the reproduction method is simply a division, accompanied by the division of nuclear machine. Representatives of this department are the largest group of prokaryotes is about 3000 species. The vast majority of дробянок гетеротрофы, a small number of autotrophs (photo-and hemoautotrofs). Eat drobyanki through absorption of nutrients through the cell wall. Among them there are aerobes and anaerobes. To drobyanka ,include bacteria, актиномицеты, миксобактерии, mycoplasma and pallidum. These microscopically small organisms is extremely widespread in all habitats. Cytology drobyanka is typical for prokaryotes: Nuclear device they are usually called nukleoid, that in translation from Latin means "similar to the kernel". Nukleoid not separated from the cytoplasm of the cell's nuclear membrane, presenting a more simple form of organization of the nuclear unit. The drobyanka lack a nucleus, there are no progressive chromosomes, and the number of them usually does not exceed one. For example, the bacterial genetic material is represented by one of the giant (usually circular) the DNA molecule. This molecule is the name of the bacterial chromosome and in electronic microscope has the form microfibbilar structure, filling the cavity nukleoid. Packing density of DNA in the nucleoids are usually lower than in the nuclei. In the cells of the дробянок strand of DNA (chromosome) is attached to any part of the cytoplasmic membrane or her appendices with the help of specific proteins. Thus, cytoplasmic membrane of the дробянок takes part in division of the nukleoid and, apparently, performs the same function as the spindle of the эукариотных organisms. It should be noted that in the nuclear unit дробянок not found proteins histones, which, as a rule, are present in the chromosomes of eukaryotes. The drobyanka unknown mitosis and meiosis; the sexual process, if it exists, is the type of copulation. The change of nuclear phase (diploid or haploid) have дробянок is not observed. Of other important differences should be noted the absence in the cells drobyanka a number of organelles, contained in the cells of eukaryotes. They have no mitochondria, but their functions are growths and folds of the cytoplasmic membrane, as well as мезосомы - complex membrane structures which are independent of the bullock, sometimes separated from the cytoplasm of its own membrane. In addition, mezosoms fulfil the function of the Golgi apparatus. These structures are known only in prokaryotes and not found in eukaryotic cells. Страницы: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 далее > Lower plants | www.fares-print.com