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Evolution & classification link

Let's explore the link between evolution & classification. Created by Mahesh Shenoy.

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Video transcript

- [Instructor] Evolution and classification are two branches of biology. One deals with figuring out how organisms evolve, how new species are born from old ones, and classification deals with figuring out how closely related two species are. In this video we're gonna see that there is a link between these two branches of biology and we're going to explore what that link is. So, let's do this by taking an example. Let's start by taking examples of classification. We classify animals, or organisms in general, by looking at common characteristics. If there are a lot of common characteristics, we will say these organisms are very closely related and if there are not so much common characteristics we will say they are not so closely related. Okay? So one question you might have immediately is what is a characteristic? So let's start over there. Let's start by defining what characteristic is. So what do we mean by this term called characteristic? I'm pretty sure you've heard of this but a definition will help. Think of characteristic as details. Details of appearance or behavior. So some examples of this could be the number of limbs that an organism has. That is a detail of appearance so that's a characteristic. You can think about their skin color, or the color of the flower, or how tall or how short they are. All these are characteristics. And to give you some details of behavior, behavior is basically how we interact with our environment. For example, whether organisms make their own food from sunlight or not. That's a characteristic. Whether organisms eat veg food or non veg food, that's another characteristic. And, other characteristics could be even how do we even acquire our own food. That's another characteristic. See, I am talking a lot about food over here. But you can think of any details of their behavior and that becomes a characteristic. So, you see, right? Characteristic is a very general term. And if two species share a lot of common characteristics, we will say they are very closely related. So let's take an example. If you take dogs and wolves, they are very closely related because they share a lot of common characteristics. If you think from their appearance point of view, there is so much common in them. The way they walk, the way they eat their food, their anatomy, their looks- look at the fur they have- their behavior also, if you think about it. They are both social animals. All of that stuff. There are so many common characteristics so we say they are very closely related. And therefore, in this diagram I put those pictures very close to each other. But if you compare a dog with say, a chimpanzee, I would say they are not so closely related. They are related of course, they also share some common characteristic. For example, for starters they're both living beings. That itself is a characteristic. Both of them have four limbs, both of them have two eyes and two ears and everything so common, but of course we also see some different features like for example, these chimpanzees walk on just two legs and these two other limbs are kind of their hands. But when it comes to dogs, they walk on all four of them. Their behavior is also not all that same. Their behavior's a little different. They also look a little different. So, not so many common characteristics and so we would say a dog is not that closely related to a chimp, compared to a wolf. It's more closer to a wolf. To throw in another example, what about human beings? Well, a human being also is more closely related to a chimp, and you might already know about this, compared to a dog. So, this is how we classify things. Based on how much common characteristics we find, we will see how closely related they are. All right, so we see that these are very closely relatives, these are also kind of close relatives and these are very far relatives. Okay? This is classification. Now the question is, based on this, what can we understand about their evolution? That's the link that we want to see. What's the link? What can we say about evolution from this picture? Well, if two organisms share a lot of common characteristics, then we can say that they evolved from a common ancestor very recently. Meaning, speciation happened very recently. Speciation is a process in which one species evolves into two or more other species, okay? And we've talked about how that happens in great detail in our previous video called Speciation. So if you need more details on that, feel free to go back and check that video. Anyways, this means if two organisms or two species are very closely related, that means their common ancestor is found in the very recent past. On the other hand, if two organisms are not so closely related- I mean chimps and humans are related, but not as close as dogs and wolves- in that case, their ancestor will not be found so recently. Our common ancestor- to find that we will have to go a little bit further back in time. So we might have to zoom out a little bit to see our common ancestor. They might be somewhere over here, okay? And so, these guys might have been around a few thousand years ago but our common ancestors will be around a few million years ago. And of course one small detail is that once the ancestors go a lot back in time, then there will be multiple speciations happening in between. So it's not these guys directly split into chimpanzees and humans. They might have first split into these two species and then they further speciated and then these further speciated and that's basically how it happens but we don't have to worry too much about the speciations happening in between. What's important is that not so closely related that means our common ancestor is further back in time. Okay, what about the common ancestors of dogs and humans? Again, our relation is very far away, right? So we will expect our common ancestor to be even further back in time. So we have to zoom out even further to get our common ancestor. These guys might have been around a few billion years ago. Now these guys might look very different from any of the dogs or the humans or the chimps. They might as well be the first mammals ever. But again, they will be found much farther back in time. Okay, just to give you one last example, what about trees and plants? Where would you put them? I'm pretty sure you would agree that trees and plants are also related to us, but not so much, right? So we might put them very far away right, because there might be only very few common characteristics. Again, we are both living, we are all made of cells, and we also both need oxygen- stuff like that. So, not so many common characters. So where do you think would be the common ancestor of plants and animals? Again, we might expect them to be a few billion years ago. And if you're wondering hey, ancestors of plants and animals- what do they look like? Then these are pretty much single-celled organisms, okay? Very basic organisms over here. And so you now see the link between classification and evolution? The more closely related animals or organisms are, the more recent their common ancestors would be. Let me write that down. That is the most important thing, okay? So, more closely related- this is about classification- then that immediately means more common characteristics and that immediately means more recent common ancestor. So this is evolution and this is classification and you can now see they are linked. And that's basically the purpose of the video. But just to complete this picture, you may be wondering does this mean that every living thing on the planet they're all related to each other and they have a single common ancestor? The answer is yes. We believe that all living things, animals, plants, insects, bacteria- any living thing you can think about that exists today- they all eventually, if you go back in time, you'll find that they all share one single common ancestor. All right? And we call that as the last universal common ancestor. There is a last ancestor for all of us. And so the big picture is, all the living beings are related to each other and eventually this might get you down to a very interesting question. You might be wondering where did these last common ancestors come from, right? These, as far as we know, might be the first living beings ever. Okay, living things ever. Might be the most simplest living things but they're the first living things ever. Then we may be wondering where did they come from? And that is up for debate, okay. We don't know the exact answers for that. You can read up theories about how living things came from non-living things. It's called abiogenesis. Great stuff to read up on, but that's something that evolution and classification don't deal with, okay? Anyways, long story short, classification is about how closely related two organisms are. More closely related means more common characteristics. And more common characteristics means more recent common ancestor. And that's how classification and evolution are linked with each other.