Homology and Homoplasy

by Jason Amores Sumpter
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Hello, everyone. In this lesson, we're going to be talking about file a genie, specifically, the difference between ancestral traits, derived traits. HM, ology and analogy. Okay, so whenever we build a file, a genie were specifically going to be looking at certain characters. Generally, you build a fella, Ginny for one character. Maybe it's a particular gene. Maybe it's a morphological character, but these characters could be any genetic morphological, physiological or behavioral characteristic that is being studied. You can pretty much study anything in a file. A genie if you want Thio and whenever you are studying, is going to be called a character. Now, generally, we're going to study different traits. Maybe it's having five fingers versus four fingers. Or maybe it's having two eyes versus one some sort of trait, and you can have different versions of that trait. You can have the ancestral version, and you can have the derived version. So an ancestral trait is a character that existed in an ancestor. It came from an ancestor. A derived trait is a modified form of the ancestral trait, so kind of like a new twist on something. But this twist was not found in the ancestor. Now, whenever we look at these two different file a genies, are they different? Well, they surely look different, don't they? But they're actually not different. The relationships between these organisms are still the same. We can see here that a and b share aim or recent common ancestor at this node. So that is the ancestor to A and B ancestor to A and B so and be are more closely related to one another than they are to species. See. And that is the same thing that is happening in both of these File A genie's Now this particular ancestor here is going to be the ancestor to a be and see, and that is the same over here as well. Okay, everyone. So even though these to file a genie's do look drastically different and A and B are arranged differently, they show us the same information. Now let's talk about the difference between ancestral traits and Dr Traits in the subject of a file a genie. So let's say that we have this particular trait. We're gonna call it Trait A, and it's found in the very first ancestor to all of these organisms trade. A is found in the bottom ancestor down here. And let's say that organism see also has trade a an organism. A also has treat a But then we're going to see that organism B has a new trait called trait be it no longer has trait A. Something is different about this organism. This is the derived trait because it is a trait that is not found in the common ancestor and trait A is the ancestral trait because it is found in the descendants. But it is also found in the ancestor. So trade is the ancestral trait because it is the same trait found in the ancestor and trade. B is the drive trait because it is not found in the ancestor, and it is a modification of the traits found in the ancestor. Now, whenever we're talking about where traits come from, whether they arise on their own or they arise via ancestry, we're gonna be talking about hm ology and analogy. Now, these two topics, these two concepts are very highly tested on and very important for you to understand. So let's go through them and let's make sure that we understand what these two topics are pointing at. Okay, so hm, ology is going to be similarity between organisms due to a shared ancestral trait. Because these organisms share an ancestor because they are closely related, they are similar, and those similarities are homologous. They are a form of hm ology. Now, if the organisms have similarities between each other, but they're not closely related, that means that thes similarities arose due to convergent evolution. Now, do you guys remember exactly what convergent evolution is? Convergent Evolution is a very important topic to understand. It's very highly tested upon topic, and this is going to be when organisms who are not closely related independently create the same tripped so convergent. Evolution is where these two organisms converge on the same idea, the same trait. But this convergence, the similarity is not due to ancestry. In fact, these organisms air not closely related whatsoever. So this is going to be similarity. That's not due to family history, but it's due to some other aspect. Maybe they live in very similar environments, so they created very similar evolutionary adaptations to combat those environments. But but But because it arose due to something else other than ancestry. We call it an analogous structure or an analogy. And this is going to be caused by convergent evolution when organisms become similar, but not because of relatedness, but because of something else. So we also have this topic of home a place e home, a place she is going to be analogous structures that arose independently. So these are gonna be very similar structures like we talked about that arose independently. A great example of home. A place is going to be winged organisms. And you guys can see these organisms right here. In this first example, we're going to have what I believe is a terrorists or some sort of, um, dinosaur, I guess. Let's say this is a pterosaur. If I can spell this terrorists or yeah, So let's say that this is a pterosaur, which would be a flying reptile or a flying dinosaur. And then the number two here is actually a bat, and number three is going to be a bird. Now all of these organisms have powered flight. They have wings that they actively flap to keep themselves in the air. That is a similar structure. Is this similar structure due to related nous. No, it's not. It's due to Homa Place e. It's due to convergent evolution thes to these three organisms. Excuse me are similar, but it's not because they're most closely related. None of the ancestors of these organisms had wings. The ancestors to birds didn't have wings. Birds arose independently to create wings. Bats are mammals. Most mammals don't have wings. So mammals arose. Sorry. Bats arose flight independently of other other other mammals. I'm sorry. I keep tripping over my words there, guys and most reptiles, as we know do not fly. So pterosaurs arose that ability to fly independently as well. So pterosaurs bats and birds arose flight independently of one another via convergent evolution and not via ancestry. So flight is not found in the ancestors of these organisms. All of these organisms evolved flight independently of what? Another via convergent evolution. So this is analogy. Okay, so that is analogy. Now, this particular example, perhaps you recognize it is a very, very famous example. This is going to be a great example of hm ology. You'll probably see this example a lot in class. Whenever your teacher is going over home Ology, This is a very, very famous example. This is going to be the four limbs of vertebrate tetrapods or four legged organisms, and we're actually tetrapods. Even though we're not four legged, we have four limbs. So tetrapods are four limbed organisms and these air all vertebrate organisms these we're gonna be humans, dogs, birds. And this is a whale. I'm covering the word, but it is a whale. Isn't it weird that whales have hands that look like our hands? So this is going to be an example of hm ology. Now, why is this? Because these organisms, all of these organisms, arose from a tetrapod ancestor that had four limbs and bones of those limbs organized in the same fashion. And if you look at the bones in the limbs of all of these organisms, they have all of the same bones. So all of the bones here in this kind of tan orangey color are gonna be the humorous. So we have a humorous and so do dogs and so do birds, and so do Wales. And they're all in the same area, the same general location in the limb. And then we're also going to have the ulna here in red, in all of these organisms. And then we're going to have the radius here in white. In all of these organisms, we're going to have the metacarpals in all of the four limbs of these organisms. That's metatarsals in the hind limbs of these organisms. And then we're gonna have phalanges in brown and all of these bones, even though they are kind of positioned slightly differently in all of these organisms. Or they have different lengths, as you guys could see in Wales. Um, they're all here, and they're all in the same pattern, Same general location, and they all are in the fore limb. All of these structures are due to ancestry because the original ancestor to the tetrapods had these limbs and these bones in this particular order and in this particular fashion. So this is all due to ancestry. They're similar due to a common ancestor. So this is an example of hm ology while flight in all these other organisms is an example of analogy. Okay, everyone All right. So now let's go down and talk about some other interesting topics. We're going to talk about different types of genes. We have or Thala Ghous jeans and parallel parallel August's. You think I know how to say that, but it is hard to say para locus jeans, and these were going to be different types of homologous genes. Remember that is due to ancestry. So an or Thala Ghous gene is going to be a homologous gene. So an ancestral gene that has sequences that are separated by a speciation event. So when a gene or when two genes are or thala Ghous, they diverged. They became different after a speciation event, but the ancestral version created these two new orthe ologists versions. Now, whenever you have a paralysis gene, this is going to be homologous genes as well, so they're gonna be similar due to ancestry. But these genes are gonna be created via a gene duplication event. So when two genes are paralysis, that means that the two genes diverged after a duplication event. So what that's gonna look like is this. You're going to have Gene a let's call it and then you're going to have a duplication event, and then you're going to have to Gina's this. This happens all the time. By the way, genes duplicate themselves via mutations all of the time and a lot of gene families. They're going to be made this way, and then you're going to have an evolutionary change. So we're gonna have evolution here. This is gonna be an evolutionary change to where we still have a gene. A because Gina is important. But that other gene a evolved and changed into a new gene called Jean B. These were going to be or thal or paralysis genes because they diverged. They changed after a gene duplication event that's going to be a paralysis gene. But they are similar because off ancestry. So these two genes are probably very, very similar, but slightly different. But they're similar due to ancestry, so they're homologous now. Horizontal gene transfer is a really interesting topic. Horizontal gene transfer is where genes are transferred from one genome to another, and you may think that doesn't happen. Very often does it actually happens a ton. Just It happens a lot in pro cryonic organisms, so pro chaotic organisms have the ability to pick up genetic material from the environment or transfer genetic material between one another, and that's going to be an example of horizontal gene transfer. So this is transmission of DNA from one genome to another pro Carry. It's very commonly do this. You carry out sometimes. Do this. Now, organelles actually do this a lot. Organelles did this during the development of eukaryotic organisms. Organelles like mitochondria actually moved some of their DNA into the nucleus. Also, transpose ons are going to do this. Plasmas are going to do this and a great example of horizontal gene transfer that happens in human beings is going to be viral horizontal gene transfer. A lot of viruses actually enter yourselves and incorporate their genetic material into your genetic material. So that is an example of horizontal gene transfer. This is different than vertical gene transfer. Vertical gene transfer is when your mother and father gave their genes to you. That is vertical gene transfer. Horizontal gene transfer is going to be two different organisms actually exchanging genetic material. So this actually is not homologous. This should be analogous because this is going to be similar genetic material, but not due to ancestry. It's due to genetic exchange DNA exchange via transpose ons via viruses or via simply too precarious exchanging genetic information. So this is similarity between organisms due to exchange not due to ancestry. So horizontal gene transfer is an analogous transfer of genetic information. Okay, everyone, let's go on to our next topic.