nCELLS: THE LIVING UNITS All organisms are cellular in nature, be they one-celled or multicellular. The individual cells are the structural units of all living things. The human body has trillions of them. Robert Hooke was the first to observe plant cells with a crude microscope in the late 1600's. In the mid-1800's, Schleiden and Schwann proposed that all living things were composed of cells. Then Virchow extended this idea by suggesting that cells arise only from other cells. Since the 1800's, research has provided us with four concepts known as the cell theory: 1. A cell is the basic structural and functional unit of living organisms. 2. The activity of an organism is dependent on both the individual and collective activities of its cells. 3. Principle of Complementarity - biochemical activities of cells are determined and made possible by the specific subcellular structures of cells. 4. Continuity of life has a cellular basis.
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This note was uploaded on 11/22/2011 for the course BSC BSC1085 taught by Professor Sharonsimpson during the Fall '10 term at Broward College.