 Okay, so we're cool with the idea that homologous structures indicate relatedness. So I've got another visual here because this is going to help us see, distinguish between homologous structures and analogous structures. The homologous structure here, this is a dinosaur, this is a bat, and this is a bird. And look at their bones. They've got their long fingers, they've got their two forearm bones and their one arm bone. One arm bone, two forearm bones, finger bones. One arm bone, two forearm bones, finger bones. Those are homologous structures. We've got a nice view again, the whale, the bird, the bat, the cat, the horse, the human. We've got it again. Look at them with all their different limbs. But guess what? Actually, we could go analogous, the wing is analogous. The bones are homologous. The bones are indicating that they're more closely related. All of these guys are closely related to each other. But the fact that they have wings, the bat and the bird are not the most closely related critters in this list because they both have wings. It would be like if we threw a fish fin up here. The fish and the whale are not the most closely related just because they both have fins. If you look deeper at their bone structure, you can go, oh, a fish doesn't have, the ray fin fish doesn't have these blobby bones, and this humerus and the radius and all the blah, blah, blah. Blah, blah, blah, be bones. So that means that those structures are analogous. They don't indicate relatedness. They basically arose on a cladogram separately from each other. The bat and the bird got wings separately just because they both have wings doesn't mean they're more closely related to each other. And if you think about the other things that bats and birds have in common, bats feed their baby's mama milk, and the mammary glands, so they can feed their baby's mama milk, have hair. They're definitely more closely related to all these mammals, except for the frog because it isn't a mammal, than it is related to the bird. They're all vertebrates, so they're all related to each other. But if we start looking at other characteristics, we're going to see that, you know what, the evolutionary relationships are not indicated by the presence of wings. This is something, I'm telling you this because this is something that we're going to use when we start looking at biodiversity. We're going to start looking at these critters and going, oh, do they, like, let's see. Do they make, do they have characteristics that indicate relatedness? And you're going to start learning them and memorizing which ones, which is related to whom based on what characteristics. Did anybody understand what I just said? Nod your head, yes. The last thing we're going to look at is the fact that you can use genetics, what, to determine relatedness?