Can you identify the major theme illustrated by each of the following examples? If necessary, you may review the themes in Chapter 1 of your book. Match the themes on the left with the examples on the right. Not all themes will be used. ResetHelp Surrounding the plasma membrane of most prokaryotic cells is a rigid cell wall, which protects the cell and helps maintain its shape. Most of the living world depends on photosynthesis, which harnesses light from the sun to produce sugar molecules. Because genes that increase resistance to cholera offer a survival advantage where the disease is common, those genes have slowly spread through the Bangladeshi population over the past 30,000 years. If you think of the cell as a factory, then the nucleus is its control center. Here, the master plans are stored and orders are given.