Cell Theory

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tsrichbio's profile pic

tsrichbio | College Teacher | (Level 1) Adjunct Educator

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The three basic tenets of the cell theory are:

1.) All living things are made of cells

2.) Cells are the smallest structural and functional unit of living organisms

3.) All cells come from preexisting cells.

The first is self-explanatory, as all living things - from microscopic organisms to the largest whale - are made of cells.  These cells can vary widely, but all living things are composed of cells.

Secondly, living organisms cannot be broken down any farther than the cell level. Like atoms and matter (atoms are the smallest units of matter), cells and living organisms are related: living organisms, at their most basic level, are made of cells.

Finally, no cell comes about in a vacuum.  All cells on the planet came from other cells. Cells divide by a number of mechanisms, such as mitosis (non-sexual cell division) and meiosis (sexual cell division), but every cell in existence came from another cell.

gsenviro's profile pic

gsenviro | College Teacher | (Level 1) Educator Emeritus

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The three statements or tenets of the cell theory are:

  1. All living beings are made up of cells.
  2. Cell is the most basic unit of life.
  3. All cells must come from pre-existing cells.

The first statement refers to the fact that all the life forms present on this planet are composed of one or more cells. The simplest life forms are unicellular, that is are made up on single cells; whereas the higher life forms (human beings, trees, etc.) are multicellular (composed of many cells). The second tenet refers to the idea that cells can carry out all the functions required for life propagation including, reproduction, maintenance, growth, metabolism, etc. And the third tenet refers to the reproduction of cells from parent cell or cells. It means that cells are born from existing cells and that's how life propagates. 

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