Cell theory

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Cell theory refers to the idea that cells are the basic unit of structure in every living thing. Development of this theory during the mid 17th century was made possible by advances in microscopy. This theory is one of the foundations of biology. The theory says that new cells are formed from other existing cells, and that the cell is a fundamental unit of structure, function and organization in all living organisms.

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History

The cell was discovered by Robert Hooke in 1665. He examined (under a coarse, compound microscope) very thin slices of cork and saw a multitude of tiny pores that he remarked looked like the walled compartments a monk would live in. Because of this association, Hooke called them cells, the name they still bear. However, Hooke did not know their real structure or function.[1] Hooke's description of these cells (which were actually non-living cell walls) was published in Micrographia.[2]. His cell observations gave no indication of the nucleus and other organelles found in most living cells.

The first man to witness a live cell under a microscope was Antony van Leeuwenhoek (although the first man to make a compound microscope was Zacharias Janssen), who in 1674 described the algae Spirogyra and named the moving organisms animalcules, meaning "little animals".[3]. Leeuwenhoek probably also saw bacteria.[4] Cell theory was in contrast to the vitalism theories proposed before the discovery of cells.

The idea that cells were separable into individual units was proposed by Ludolph Christian Treviranus[5] and Johann Jacob Paul Moldenhawer[6]. All of this finally led to Henri Dutrochet formulating one of the fundamental tenets of modern cell theory by declaring that "The cell is the fundamental element of organization"[7]

The observations of Hooke, Leeuwenhoek, Schleiden, Schwann, Virchow, and others led to the development of the cell theory. The cell theory is a widely accepted explanation of the relationship between cells and living things. The cell theory states:

  • All living things or organisms are made of cells and their products.
  • New cells are created by old cells dividing into two.
  • Cells are the basic building units of life.

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