In this lecture, as well as in the previous one and the next one, I tackle areas of Biology where I am really weak: origin of life, diversity of life, and taxonomy/systematics. These are also areas where there has been a lot of change recently (often not yet incorporated into textbooks), and I am unlikely to be up-to-date, so please help me bring these lectures up to standards…. This post was originally written in 2006 and re-posted a few times, including in 2010.