Briefly give the contributions of the following scientists in formulating the cell theory.
a) Rudolf Virchow
b) Schleiden and Schwann
Ans.
The Cell Theory was first proposed by Schleiden and Schwann in 1838-39. In their theory, they stated that
(1) All living beings are products that are formed by one or more cells.
(2) Cells are the structural and functional units of life.
A third statement was added to this theory by the works of Rudolf Virchow. The cell theory was thus expanded to three statements –
(1) All living beings are products that are formed by one or more cells.
(2) Cells are the structural and functional units of life.
(3) New cells come from pre-existing cells. The last statement was the contribution of Virchow who through his experimentation, proved that cells arise from the pre-existing cell and not through crystallization as was proposed by Schleiden and Schwann earlier.
All the three scientists helped in paving the way to formulate the modern cell theory. Main points of the modern version of cell theory are-
(1) All living beings are made from one or more cells.
(2) Cells are formed from the pre-existing cell.
(3) Cell is the functional and structural unit of life.
(4) Energy flows within cells.
(5) All cells have the same basic composition.