The Cell Theory by ePLf8642


									The Cell Theory

   Biology 11
   S. Dosman
              What are cells?
• Cells are defined as the smallest unit of life.
• All living things are either unicellular
  (composed of only one cell) or multicellular
  (composed of more than one cell).
                    Robert Hooke
• In 1665, English scientist
  Robert Hooke discovered
  cells while looking at cork
  under his primitive
  microscope .
• Hooke first viewed cells in a
  thin slice of cork. He named
  them “cells” as they
  reminded him of the shape
  of the cells (rooms) in a
Cork cells
     • Hooke did not realize
       that what he was seeing
       was the cell walls and
       the empty space inside
       the dead cork cells.
     • So although he was the
       first to see cells he did
       not fully understand
       what he was seeing.
         Anton van Leeuenhoek
• Anton von Leeuenhoek
  was one of the major
  contributors to the
  invention of the
• In 1674, Leeuenhoek
  first described living
  cells – blood, bacteria &
  unicellular pond
                Robert Brown
• Robert Brown was a
  Scottish botanist who is
  credited with naming
  the nucleus of the cell
  around 1820.
• The nucleus had been
  observed before
  however he was the
  first to name it.
                Felix Dujardin
• In 1835, Felix Dujardin
  recognized the
  existence of one-celled
  organisms and that
  protoplasm seemed to
  be associated with all
  forms of life.
             Matthias Schleiden
• In 1838, the German
  botanist Schleiden
  stated that all plants are
  composed of cells.
             Theodor Schwann
• One year later in 1839,
  another German
  physiologist named
  Theodor Schwann
  stated that all animals
  are composed of cells.
              Rudolph Virchow
• In 1858, the Polish
  scientist Rudolph
  Virchow made a very
  important generalization
  that all cells come from
  other cells.
• In other words, all cells
  come from pre-existing
 And after many, many years we
 have what many refer to as the
cornerstone of modern Biology….
            The Cell Theory
1. All living things are composed of cells.
2. The cell is the basic living unit of
3. All cells arise from pre-existing cells.

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