In my evolutionary biology class, my professor is having us do problems with phylogenies that go like this: we are given three or four possible phylogenetic trees, along with a grid. The y-axis represents specific base pairs, and the x-axis represents specific species. So we're essentially given a genetic sequence for four or five different species. Then, we have to mark specific mutations on the branches of the trees, count them up, and determine which phylogeny is the most parsimonious. I would sincerely appreciate it if anyone could direct me to a website or tutorial of some kind that elucidates this concept. I already looked, but couldn't find anything. My textbook has a website, but it's completely useless. I feel like an idiot because everyone else seemed to understand it, and I know it has to be much more simple than I'm making it out to be. But something in my mind just isn't clicking.