1838 • Matthias Jakob Schleiden German botanist, conclud ed the all plant tissues are composed of cells.
1839• Theodor SchwannGerman zoologist, concluded that all animal tissues are composed of cells.Proposed the cell theory
1858• Rudolph VirchowCompleted the cell theory by expounding his famous conclusion “omnis cellula e cellula” or cells develop from pre- existing cells.
Cell Theory According to Schwann1) The cell is the unit of structure, physiology, and organization in living things.2) The cell retains a dual existence as a distinct entity and a building block in the construction of organisms.
Continued…3) Cells form by free-cell formation, similar to the formation of crystals (spontaneous generation).
Spontaneous GenerationThe hypothetical process by which living organisms develop from nonliving matter.
Redi’s Experiment the Disprove Spontaneous Generation
Revised Cell Theory1. all known living things are made up of cells.2. the cell is structural & functional unit of all living things.3. all cells come from pre-existing cells by division. (Spontaneous Generation does not occur).