Cell Theory--论文代写范文精选

51Due论文代写网精选paper代写范文：“Cell Theory ” 这篇生物学paper代写范文介绍了细胞理论的发展，1838年,马蒂亚斯,德国植物学家观察到细胞结构在植物的单位,因此提出了著名的细胞学说。1839年,一位德国动物学家西奥多,发展了这一观点，解释了动物细胞的概念,即所有的生物体都是由细胞构成的。细胞理论源于大量的调查。细胞学说的追随者雷马克,Nageli Kollikers等人,他们展示了细胞分裂，从而基因得以延续的基础。(论文代写)

In 1838, Matthias Jacob Schleiden (1804-1881), a German Botanist, observed nucleoli and said that cells are the units of structure in plants, thus formulating his famous cell theory. In 1839, a German Zoologist Theodore Schwann (1810—1882), extended this view of cell concept to animals, i.e., all organisms are composed of cells and cell products.

This cell theory resulted from numerous investigations, i.e., of Mirbel (1802), Oken (1805), Lamarck (1809), Dutrochet (1824) and Turpin (1826) and finally by Schleiden (1838) and Schwann (1839). Although Schleiden and Schwann are universally recognised as the founders of cell theory, but its significance was earlier realized by Leeuwenhoek, Grew, Malpighi and others.

Wolff (1759) clearly demonstrated the ‘spheres’ and ‘vesicles’ composing the various parts of body. Later, Meyen, Von Mohl and Raspail clearly defined the cells and thus formulated the cell theory, which was developed by Schleiden and Schwann.

The immediate followers of cell theory were Remak, Nageli and Kollikers, etc., who demonstrated the cell division as basis of genetic continuity. Virchow applied the cell theory to pathology and Kolliker extended it to embryology and he demonstrated that organism develops from the fusion of two cells—the sperm and the ovum.

Brown (1831) established that the nucleus is a fundamental and constant component of the cell. Dujardin, Schultze, Purkinje and Von Mohl concentrated on the description of the cell components, termed the protoplasm. Thus, the cell is a mass of protoplasm limited in space by a cell membrane and possessing a nucleus.

Recently, organismal theory has been introduced, according to which an organism is regarded as a protoplasmic unit which is incompletely divided (Z-44/C.B.) into small centres, the cells, for the performance of various biological activities.

It is just a modified interpretation of cell theory. Laurence Picken, in “The organization of cells” (1960), accepts cell as an organism. “At its own level of organization it is a unity, and it remains a unity, though without analytical mental-equipment we conceive it more easily as a plurality of discriminated organelles.”(论文代写)

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