Outline the main provisions of the cell theory.

1.the cell is a structural and functional unit, as well as a unit of development of living organisms
2.all cells have a similar structure, chemical composition and general principles of life
3.cells are formed only by division of the cells preceding them
4.cellular structure of organisms – evidence that all living things have a single origin
5. there is no life outside the cell, non-cellular forms – viruses – show signs of living only in the cell.