We tackled a number of very big issues in today's class. Probably too many, as none of them got the level of development they deserve.
The clicker questions didn't work. This was my own fault; I had assumed (hoped) that deleting the PRS logo from a slide would delete the associated clicker question, but instead it just created a mismatch between the questions and the slides that sent the PRS software into a tizzy. So we did the science questions by shows of hands, which was fine.
In both classes students raised a point I hadn't anticipated, that phylogenetic trees usually have the deepest branches on the left. I wonder if they learned that in high school. I'm pretty sure this isn't an explicitly-stated convention, but it is commonly done.