Cells Unit Review 1. What are the three parts to the cell theory? 2. What are some examples of Internal Stimuli? 3. What are some examples of External Stimuli? 4. Explain Phototropism. 5. Explain photosynthesis. 6. Explain respiration. 7. What are organic compounds? What elements are in organic compounds? 8. List the levels of organization from smallest to largest. 9. In an experiment there are three types of variables. Explain each type of variable. 10. Fill in the following chart. 11. Fill in the following chart. 12. Fill in the following chart.