Describe the basic principles of cell theory giving examples to support them

The cell is the smallest unit of life. Organelles cannot survive by themselves.Challenge to the theory: green algae - highly complex mono-nucleated cell that is up to 10cm. All cells come from pre-existing cells. Replicate by either mitosis or meiosis. Highly complex; nothing less intricate has been known to work. DNA is universal; most likely because cells came from a single common ancestor Exception: first cell. This was made from simpler compounds coming together under the right conditions. Urey and Miller Experiment shows that a form of primordial cells can form under the right conditions.Every living organism is made up of cells.All examples of living growth arise from multiplication of cellsChallenge: viruses - considered non living by most. Too simple and relies on cells to replicate.