 Now we're just going to build a tree with actual critters. So rather than having names of critters, I had to bring the pictures back because I love these pictures. And these are the pictures of the critters that we already looked at. So if I gave you this pile of critters and said, okay, sort them out, like who's related to who, you probably would be like, okay, yeah, we got to throw the mammals together and we got to throw the birds together. You agree with that? Like we got to kind of sort them by similarity. And that, again, is super intuitive, but the power of the tree or thinking, the tree thinking process, is that now we can come in and we can say, okay, let's build in the lines and actually indicate the fact that these guys share a common ancestor. And we can even think through, like what are some traits that that common ancestor might have? Traits that both of these guys share. Do you think the common ancestor had a white face with black eyes? It's possible. The ancestors are hypotheses. We don't know what they actually looked like. We have a pretty darn good sense that these two critters are closely related to each other, but we don't know what the critter looked like that gave rise to both of them. And chances are pretty excellent that that critter did not have, that critter, that ancestor, probably didn't look like a panda. Probably didn't look like a gorilla. But there are some characteristics that it probably had, and what do you think some of those might be? How about it had hair? Definitely. Like that's a characteristic of mammals. In fact, all mammals share that characteristic. It probably had, you know, these are important. Memories, memory glands, milk makers, breasts, breasts that make milk. All mammals have those things. The ancestor that gave rise to these guys probably had those things. Does that make sense? Now, do you think? We can do the exact same thing on the other side. We can say, okay, these guys are probably closely related to each other. And let's just think it through. Like what kind of characteristics do these guys have that they share with each other? We're going to be highly un-technical at this point. Let's practice for the kind of thing you're going to do in lab. They all have beaks. They all have feathers. They all have, that says feathers. They have hollow bones. They breathe in circles. Oh my gosh, birds are so cool. They can actually inhale and exhale at the same time so that they have like this flow of air in the lungs that is circular, not in, out, in, out, way more efficient. Awesome. There are other things that these guys have in common with other birds. But we also said that they're all what? Well, we got a whole bunch of options that we could say. And in fact, I'm going to say, I'm going to put these in an all group that is more narrow than the all group that we were going with earlier. We did say they're all animals. Remember when we said that? And so we could say this ancestor was just an animal. It had characteristics that all animals have. But we actually know that there are some even more specific similarities with these guys. All animals have a vertebral column, vertebrae, vertebrae. Not all animals have that, but all mammals do, and all birds do. So we can say that their ancestor, the ancestor shared by both of these guys, probably had vertebrae. Does that make sense how that works? It's not all, like I said, it's a hypothesis. We could say we're the ancestors, and then we could talk about relatedness in reference to the ancestors. So I could again say, name the ancestor, the most recent common ancestor shared by the gorilla and the panda. And you would be like, hello, it's ancestor A. I could say, tell me about ancestor A. Ancestor A, like what do you think it looked like? We had hair and mammaries. Got it? What's the most recent common ancestor shared by panda and crown crane? Follow it back, follow it back. It's got to be C. What's the characteristic that that ancestor probably had? Vertebrae. That is building a tree. You can think about your trees and think about how closely things are related to each other. We're going to spend a lot of time with trees, doggies. So if you are feeling like your eyes are crossing, uncross them. I'm going to tell you one more thing about trees that is kind of weird. These things are called nodes. Nodes, and we know already that the nodes represent ancestors. And are you ready for this? Trees can rotate around nodes. So if we put gorilla and panda on this tree, it doesn't matter if we put the gorilla on the left or the panda on the left, like it doesn't matter. We can actually spin the tree at the node. And the relationships that are demonstrated are exactly the same. So it doesn't matter how we put them up there. And that's a really important piece of the puzzle. I'm going to give you a set of critters and you have to build your own tree next. Can I just do it?