Cell Theory
1839
Proposed by Theodor Schwann (1810–1882)
and Matthias Jakob Schleiden (1804–1881)
1. All living
organisms are composed of one or more cells.
2. The cell is the
basic structural and functional unit of all living things.
The third tenet was
proposed by Rudolf Virchow, a German Pathologist (1821–1902) in 1855
3. Cells arise from
pre-existing cells “Omnis cellula e
cellula” (by cell division; mitosis or meiosis; not derived
from spontaneous generation)
Background:
Schleiden in 1838, German
botanist, found out cell as the basic unit of plant structure.
Theodor Schwann, a German
physiologist in 1839 defined cell as the basic unit of animal structure
also. In 1839, they together proposed the two statements of the present cell
theory.
Modern Cell Theory
The knowledge of the
advancement in the field of molecular biology, biochemistry, etc. is considered
to make the following additions to the above classical cell theory
4. Cells contain
heredity information in their DNA. This information is passed to new cells by
cell division.
5. All cells have the
same basic chemical composition.
6. Energy flow
(Metabolism and biochemistry) occurs within cells.
The
other major contributors to the Cell Theory are Robert Hooke; who coined the
tern “cell” and Antonie van Leeuwenhoek; who was the first one to observe
living organisms under his own microscope.
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