Biology 104 Lecture 9 Biology 104 - Lecture 9 Organization of Cells September 13 1.
Cells are the basic units of life.
All organisms are composed of at least one cell. There is no other form of life. Viruses are not really living since cannot exist alone, only with cells to infect. Life progresses by enlarging and dividing cells. This was not clear for a long time, however, because cells are so small that the invention of microscopes was needed to see them.