Низшие растения

Lower plants Algae and mushrooms [#] Navigation Main Virus Department drobyanka Algae Friends Recommend Introduction Until recently it was believed that the organic world consists of two kingdoms - plants and animals. The plants in their turn were divided into higher (300-350 thousand species) and lower (about 150 thousand species). The body of higher plants separated on vegetative organs: by leafy shoots, carrying out the functions of photosynthesis and holding substances, and the roots, with the help of which the plants are attached to the soil and extract from it the water and mineral salts. The lowest are plants, in which the body does not расчленено on vegetative organs, and there is a thalli (tull). They have no conductive vascular system, and the female sexual organ (where it is) is almost always one-celled as opposed to многоклеточному female genitals of higher plants. Presentation of only two kingdoms of nature has been shattered in the first quarter of the XX century in connection with the detailed study of cell structures of the different organisms. These researches have allowed to divide all living organisms on the prokaryotes and eukaryotes. The first are the organisms in the cytoplasm of which there is no separate kernel, and there are one or a few locations with a high concentration of DNA (deoxyribonucleic acid). These areas are called nukleoids or nukleoplazma. Nukleoid - more than a simple form of organization of the nuclear unit. The prokaryotes it qualitatively differs from the nuclear unit in eukaryotes. The prokaryotes no nucleus, there are no progressive chromosomes, have not found the proteins histones, no mitochondria and plastids, a number of other cell inclusions, known in eukaryotes. The prokaryotes in the cells there are mezosoms - complex membrane of education, the forming of cytological membranes. Some prokaryotes are known gas vacuoles, allowing them float freely in the water, not sinking to the bottom. Unlike fungi and algae in the composition of the cell walls of prokaryotes no chitin and cellulose. The basis of the cell walls of the prokaryotes is glikopeptid (mukopeptid) - mureid. In mobile prokaryotes more simply than in eukaryotes, arranged flagella. The prokaryotes are unknown mitosis and meiosis. The sexual process, or missing, or passes on the type of conjugation. The change of nuclear phases of the prokaryotes is not observed, their cells always haploid. The group of prokaryotes is about 3,000 species. In their composition includes two divisions: drobyanka (mycoplasma bacteria, actinomecit) and blue-green algae (cyanobacteria). Separately are not cellular organisms, viruses and viroids. Some scientists identify prokaryotes an independent kingdom. Pages: 1 2 3 4 далее > Lower plants | www.fares-print.com