•HISTORY OF THE FORMULATION OF CELL THEORY
In the history of biology, ancient Greeks were the first who organized the data of natural world Aristotle presented the idea that all animals and plants are somehow related Later this idea gave rise to questions like is there a fundamental unit of structure shared by all organisms?" But before microscopes were first used in 17th century, no one knew with certainty that living organisms do share a fundamental uniti e cell.
Cells were first described by a British scientist, Robert Hooke in 1665 He used his self made light microscope to examine a thin slice of cork Hooke observed a Thoneycomb of tiny empty compartments He called the compartments in cork as cellulae His term has come to us as cells (Figure 4.5) The first living cells were observed a few years later by Dutch naturalist Antonie van Leeuwenhoek He observed tiny organisms (from pond water) under his microscope and called them as " animalculer".
For another century and a half the general importance of cells was not appreciated by biologists In 1809. Jean Baptist de-Lamarck proposed that no body can have life if its parts are not collular tissues or are not formed by cellular tissues In 1831. a British botanist Robert Brown discovered nucleus in the cell In 1838, a German botanier Matthias Schleiden studied plant tissues and made the first statement of call theory. He stated that all plants are aggregates of individual cells which are fully independent One year later in 1839 a German zoologist Theodor Schwann reported that all animal tissues are also composed of individual calls Thus Schleiden and Schwann proposed cell theory in its initial form
In 1855 Rudolf Virchow, a German physician, proposed an important extension of cell theary He proposed that all living cells anse from pre-existing cells ("Omnis cellula e cellul) In 1662 Louis Pasteur provided experimental proof of this idea
Cell theory is regarded as one of the most fundamental knowledge in biology It has wide ranging effects in all fields of research. After the initial presentation of cell theary by Schleiden and Schwann many details of cells were studied and call theory was extended Cell theory, in its modern form includes the following principles
1. All organisms are composed of one or more cells
2. Cells are the smallest living things the basic unit of organization of all organisms
3. Cesarise only by divisions in previously existing cells
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| HISTORY OF THE FORMULATION OF CELL THEORY |
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