1.Basic unit of life

 In 1665, Robert Hooke observed a section of a cork using a microscope prepared by him. He discovered a structure like chambers in a beehive and he named them as cells.
Schleiden, Schwann and Radolf Virchow introduced the cell theory, based on the facts revealed by observing different live tissues through the microscope. The contents of the cell theory are as follows. 
  1. The structural and functional unit of life is the cell. 
  2. All organisms are made up of one or more cells. 
  3. New cells are formed from pre-existing cells.

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