Cells and Cell Theory: Grade 11 Biology.
CELLS & THE CELL THEORY
Cells were discovered by Robert Hooke in 1665.
The Cell Theory states:
1. All living organisms are composed of cells. They may be unicellular or multicellular.
2. The cell is the basic unit of life.
3. Cells arise from pre-existing cells.
The modern version of the Cell Theory includes the ideas that:
- The activity of an organism depends on the total activity of its individual cells.
- Heredity information (DNA) is passed on from cell to cell during cell division.
- Energy flow (metabolism) occurs within cells.
- All cells have the same basic chemical composition.
There are two different categories of cells:
- Eukaryotes have distinct nuclei bound by a nuclear membrane and membrane-bound organelles (mitochondria, chloroplasts, lysosomes, rough and smooth endoplasmic reticulum, vacuoles).
There are four kingdoms of eukaryotes: Animal, Plant, Fungus and Protist