2.1 Discovery Of Cell And Cell Theory
In early classes we have studied that all living organisms are composed of cells. The question arises here how did biologist come to know that, obviously through observations. These observations started with the discovery of magnifying glasses and later on with the development of microscope. (Latin word micro = small; skopion = to see). In 1610 Galileo, an Italian astronomer and physicist developed microscope to observe small organisms. In 1665, Robert Hook made an improved microscope by combining lenses, called compound microscope and examined a slice of cork under it. He found small honey comb like chambers, which reminded him small rooms of monastery and are said cellula in Italian, so he also named these structures as cellulae or cell (small rooms). The cork was made from bark of oak, so he actually saw the cell-wall only.
in 1842, Dutrochet, boiled plant material in nitric acid and then examined under microscope. It was found to consists of cells. In 1831, Robert Brown discovered a spherical body, the nucleus in the cells of orchids. Schleiden (1838) a German botanist, proposed that all plants are made up of cells. Next year another German Zoologist, Theoder Schwann stated that all animals are made up of cells. He observed nuclei in all types of animal cells but failed to observe cell-wall in them. From here the difference between plant and animal cell started to establish. In 1858, Rudolf Virchow stated that new cells come only from other cells i.e animals cells come from animal cell and plant cells from plant cell. The combined efforts of Schleiden, Schwann and R.Virchow finally gave rise to cell theory. The salient features of the cell theory are as under:
In early classes we have studied that all living organisms are composed of cells. The question arises here how did biologist come to know that, obviously through observations. These observations started with the discovery of magnifying glasses and later on with the development of microscope. (Latin word micro = small; skopion = to see). In 1610 Galileo, an Italian astronomer and physicist developed microscope to observe small organisms. In 1665, Robert Hook made an improved microscope by combining lenses, called compound microscope and examined a slice of cork under it. He found small honey comb like chambers, which reminded him small rooms of monastery and are said cellula in Italian, so he also named these structures as cellulae or cell (small rooms). The cork was made from bark of oak, so he actually saw the cell-wall only.
in 1842, Dutrochet, boiled plant material in nitric acid and then examined under microscope. It was found to consists of cells. In 1831, Robert Brown discovered a spherical body, the nucleus in the cells of orchids. Schleiden (1838) a German botanist, proposed that all plants are made up of cells. Next year another German Zoologist, Theoder Schwann stated that all animals are made up of cells. He observed nuclei in all types of animal cells but failed to observe cell-wall in them. From here the difference between plant and animal cell started to establish. In 1858, Rudolf Virchow stated that new cells come only from other cells i.e animals cells come from animal cell and plant cells from plant cell. The combined efforts of Schleiden, Schwann and R.Virchow finally gave rise to cell theory. The salient features of the cell theory are as under:
i) All living organisms are composed of one or more cells.
ii) The cell is the smallest, basic structural and functional unit of all organisms.
iii) New cells are formed by the division of pre-existing cells.
ii) The cell is the smallest, basic structural and functional unit of all organisms.
iii) New cells are formed by the division of pre-existing cells.
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