Cell Theory : The Development & It's Significance

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The cell theory is mainly proposed by Schleiden and Schwann, 1839. According to cell theory all living organisms ( bacteria, plant and animal ) are composed of cell. The cell is the basic structural & functional unit of life. The activities of all living organisms are the result of the actions of their cells. The cell theory is important to understand the development of organisms and living beings. It is also important that any small changes affect the activity of living being.

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A Plant Cell
A Plant Cell

Attribution Of Scientist In The Development Of Cell Theory / Brief History Of Cell Theory

  • Robert Hooke, 1665 : The discussion about cell theory has been started after the discovery of cell by Robert Hooke.
  • Lamarck, 1809 : Life is not possible for a living being whose organs are not made up of cellular tissues.
  • M. J. Schleiden ( Botanist ) and Theodor Schwann ( Zoologist ) , 1839 : All plants and animals body are composed of cell. Schwann saw that animal cell is surrounded by a thin layer in spite of a thick cell wall. He called this thin layer as plasma membrane.
  • Rudolf Virchow, 1858 : He expands the cell theory and proposed a famous quotation, “Ommis cellula - e – cellula” means “The origin of all living cells is performed by pre-existing cells.”
  • Louis Pasteur : Louis Pasteur supported the Virchow’s cell theory by his experiments. His experiment’s main point are as follows - 
    • The body of all living being is made of one or many cells.
    • Cell is the basic structural and functional unit of living being.
    • The origin of all cells is performed by the pre-existing cells.
    • Living cells are totipotent and can convert into a fully developed living being in a specific condition.

Essential Features Of Cell Theory

  • Cells are the structural and functional unit of a living being.
  • All life-related activities take place in each cell.
  • Cells are the units of metabolic activities.
  • Cells are also genetic units.
  • New cells are formed only by the division of pre-existing cells.
  • The biological functions of an organism are the result of the integrated actions of its cells.

Significance Of Cell Theory

  • The basic structure of cells found in any living creature and any part of the body is the same. All have an outer covering of cell membrane. All have cytoplasm and nucleus inside it. This shows structural unity.
  • The basic functions like nutrition, respiration, excretion, reproduction etc. are definitely completed in all types of cells. This shows functional unity.
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Exception Of The Cell Theory

  • Virus is the exception to the cell theory.
    • The essential metabolic system is absent in the virus for biological activities.
    • Virus is a microscopic, living infectious particle, which has the capacity to expend the infectious diseases.
  • There is a lack of an organized nucleus and most of the cell organelles in a Prokaryotic cells such as bacteria, blue – green algae etc.
  • Mature RBC’s and sieve elements of plant cells possess cytoplasm, but there is a lack of nucleus in it.
  • Voucheria ( an algae ) and Rizopus ( a fungi ) have more than one nucleus in its cytoplasm, which is against the cell theory.

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