Cellular Level Organization

A. Cell Theory
1. All organisms, both unicellular and multicellular, are made up of cells.
2. Cells are the smallest units of living matter and structural and functional units of all organisms.
3. In 1830's, Mathias Schleiden (plants) and Theodore Schwann (animals) declared organisms were made of cells.
4. Cells are capable of self-reproduction; Rudolf Virchow declared cells come only from preexisting cells.
B. Cell Size
1. Cells range in size from a frog's egg (one millimeter) down to one micrometer.
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