How is the evolution of photosynthesis connected to the endosymbiotic theory?
First let me correct your last statement. Evolution is a theory about the origins of biological diversity on earth. Photosynthesis is a process by which plants and other organisms convert light energy into chemical potential energy that organisms can use for cellular processes. As we usually think about it, photosynthesis allows plants to “fix” the carbons from carbon dioxide into sugars. Fortunately for us, we have a way to break down the sugars in starch, and convert that chemical potential energy back into something we can use directly for stuff we want to do (e.g. ATP to allow you to move, think, build stuff, and reproduce). Endosymbiosis starts out with one cell engulfing another. Usually when a cell does this, it digests the cell it has engulfed (see videos of amoebae on YouTube). But in endosymbiosis, that doesn’t happen. Somehow the cell that has been engulfed continues to live inside the other one, providing it with some benefit. Over time and many generations, each becomes so
