what is cell theory? Hawa who gave cell theory
Answers
What a cell is?
The basic structural and functional unit of life that is capable of doing all the functions necessary for being alive is callled as cell. A cell is capable of independent existence and performing all the functions that are essential for life. Anything or any organism that is less than a complete structure of cell doesn't ensure independent living. This is why viruses are considered connecting link between living and non living organisms. Viruses attack the host cells and use their cellular functions to divide. Hence, cell is known as the fundamental or basic unit of life.
Cell was discovered by Robert Hooke in 1665. Later, Anton Von Leeuwenhoek discovered and described living cells.
In 1838, a German botanist named Matthias Schleiden studied various a large number of plants and observed that all plants are composed of different kinds of cells. About the same time in 1839, a British Zoologist named Theodore Schwann observed different types of animal cells. Based on his observations, he proposed that animals and plants are composed of cells.
This led to the formation of cell theory. Cell theory was formulated by both Matthias Schleiden and Theodore Schwann. But, this theory still lacked something that was "how new cells are formed?" In 1855, Rudolf Virchow added that all cells arise from pre existing cells. He gave the statement "Omnis cellula-e cellula" i.e., new cells arise from pre existing cells. Therefore, the hypothesis of Mattias Schleiden and Theodore Shwann was given final shape of cell theory by Robert Virchow. Hence,the present form of cell theory is as follows :
(i) All living organisms are composed of cells and products of cell.
(ii) all new cells arise from pre existing cells.
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The cell theory is comprised of the following postulates :-
1. All organisms are composed of cells and cell products.
2. All metabolic reactions takes place in cells. Thus , cells and structural and functional unit of life.
3. All cells arise from preexisting cells only. No cell can originate spontaneously but comes into being only by division of already existing cells.
4. Every organism start its life as a single cell. Viruses on exception to cell theory.
The two scientist , Jacob Matthias Schleiden , a German botanist , first proposed idea that all plants are consists of cell and after , Theodor Schwann , a German Zoologist , independently asserted that all animals and plants are made up of cells.
This joint finding forms the basis of cell theory and these two scientist are referred to be the proposer of the cell theory.