 Hi, darlings, we're here to finish our conversation about evolution. Actually, this is the third of our lectures on evolution, but as I said before, I believe we're not going to stop talking about evolution for the rest of the semester because what's coming next is biodiversity. And we can't really appreciate biodiversity without looking at it through an evolutionary lens. So today, our task is to look at some of the evidence for evolution. And much of the evidence, I mean, there is actually a significant amount of evidence of macro evolutionary processes at work. I think the most compelling things to look at are macro evolutionary processes at work. So we're going to start out this lecture with a reminder of what macro evolution is and then some mechanisms. Like how do we go from one population to two populations made up of different species? Like what is that process that gets us there? And then as we go through speciation over like massive quantities of time, what do we end up with? What is the evidence that we can see that this actually took place? So let's remind ourselves, speciation. Remember my metal arcs? These actually are two different species of birds as opposed to our ants. We're the same species of ants, which means that talking about species actually becomes rather challenging and difficult. But we can look at our cladograms where we've been mapping evolutionary relationships and we can see moments of speciation, moments where... Now, please keep in mind that this cladogram is representing like thousands and millions and billions of years. So I don't know what the exact time is for this little. I mean, these don't even look that different, do they? But they are different species and at some point in the past, some number of years ago there was a speciation event. What was that? How did that happen? That's macroevolution and that's what we're going to talk about. So we've got a couple of pieces where we're going to look at the mechanism of speciation and then we're going to start looking at the evidence that speciation has taken place in the past. All right, so the first thing we have to talk about is what starts speciation and how it... why did the Drosophila dentissima decide to become a deer? Like what happened to branch dentissima off from melanogaster? Why did that happen? Why did this speciation event take place?