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Current time:0:00Total duration:12:41

Taxonomy and the tree of life

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Video transcript

this right here is a picture of Carl Linnaeus and I'm sure I'm mispronouncing the word and he's a Swedish gentleman who lived in the 1700s and he's known as the father of modern taxonomy and the word taxonomy if you just split it up into its original root it really is the science of really classifying things but when people talk about taxonomy in this particular in Carl Linnaeus case they're talking about the classification of living things so classifying classifying organisms and his real innovation before he came about people realized that you had species of animals that Lions had certain properties that made them all Lions that they could interbreed and things like that that monkey or chimpanzees would all interbreed and that would be a separate species and that polar bears were separate species and that humans were a separate species but what he really brought to the table is he decided well let me just not just group animals into species maybe I can group species into into other categories and that's where we get the genus from you group similar species into a genus and then he went even beyond that because even the idea of grouping things into a genus would dated back to the ancient Greeks he said well why don't I group similar Genesis together into orders orders together into classes and then classes together into kingdoms so really what he did is he said well maybe I can classify I can create a tree I can create a tree of life I can create a structure so we can really see how far apart any two organisms are and so that's why he's really the father of modern taxonomy and he did not have many tools all he could do is look at the power and his powers of observation says ok those kind of animals they have fur or they reproduce in this way or they lay eggs or they don't lay eggs or they have spinal columns or they don't have spinal columns so that's the best that he could do when he did his taxonomy but since then there's obviously been tons of innovations and how we perceive animals or the natural world and our tools for studying them so one thing that he did not know about is evolution this idea of common intra common ancestry and between our understandings of evolution and our ability to look back at the fossil record that helps us get more precise at figuring out which animals are related to which we can see do they have a common ancestor more recent or further back and what even Charles Darwin didn't have which we now use as a tool in taxonomy is that it is the genetic evidence so now we don't even have to rely on the fossil record we can look at the DNA of two species that exist today and see how similar are though is that DNA and that tells us how recently they branched apart if we were able to find it in the fossil record or how recently in the past did these two species become two different species now with that said I do want to make this clear and this is something that you know I've always had a little bit was fuzzy for me the first time that I was exposed to this idea of taxonomy is that taxonomy is as much an art as it's a science and today even to this day people are debating about the best way to classify things and how what do you pay attention to and DNA has been the best tool so far and giving us a more systematic a more analytical way of deciding how close to animals are but to a large degree a lot of these categories the deciding we're divided along kingdom phylum class order family tribe these are somewhat arbitrary these are just picked based on early taxonomists including Carl Linnaeus and saying oh this looks like a grouping right over here but they could have grouped at a broader level or a deeper level so these things right over here are somewhat arbitrary a more analytical way just to see how much DNA you have in common and then use that as a measure of how far apart two animals are or really I should say two species are because this taxonomy doesn't even apply just to animals it applies to plants and bacteria and and archaea and all sorts of things so it's actually a broader thing than just animals now with that out of the way what I thought would be fun just so that we could really get a sense of where modern taxonomy is where the field that was essentially fathered by Carl Linnaeus where it is now how we and and use that to figure out where we humans fit into the big picture and obviously I'm drawing just a small fraction of the universe of the organisms that we even know about right now but at least it frames the picture in terms of something we understand in particular us in particular humans now our species we call ourselves humans but we're really Homo sapiens and the sapiens is the species part and then homo is the genus and what I'm doing right over here is I'm saying well if the home was the genus what other what other species were inside of homo and the reality is or at least as far as we know there are no other living species inside inside of homo that we we probably killed them all off or did or maybe we interpreted with them somehow which might have argued that maybe they weren't different species but more likely they were competing in the same ecosystems and they became injured endangered species very quickly when they competed with our ancestors but the most recent other species within the genus that we know about are the Neanderthals and the formal were the formal the formal term for their species is neanderthalensis now if we go further up the tree of life further up to the taxonomy and you'll sometimes see tribe mentions sometimes you won't and we tend to get a little bit more granular the closer we get to humans when we go further away in the Tree of Life we get a little bit less granular sometimes but that's not always the case as well you go a little bit further up then you get to home it home and Nene and I'm sure I'm mispronouncing some of this as well but the other another species that's in homo nene that is not in homo and I'm definitely not listing all of them and that's why I'm showing all of these other branches all of these other branches over here is what we call the common chimpanzee and their species name is there there's their genus is pan and their species is troglodytes so you would refer to them as Pan troglodytes and that's also another convention that Carl Linnaeus came up with is that you refer to a particular species by its genus and then its species and you capitalize the genus and you lowercase a species so we're Homo sapiens this is Homo neanderthalensis this is Pan troglodytes or often referred to as chimpanzees now if you go up one one higher level of broadness on this tree of life you then get to the family and we are in the family home in a day and hominid day and I'm sure I'm mispronouncing it once again but just to give you an example so everything I've listed so far everything I've talked about so far are within this family and to show you an animal that is not in this family you just have to look at the gorillas and you could call it the gorilla knee the gorilla knee Gorrell any gorilla or G gorilla that's that's its actual species name and this family right over here sometimes the common term is the great apes the great apes now you go one further level and this is the whole reason why I'm doing this and I'm not by any means am I being exhaustive about the other other species that are in that family but that are not in our tribe I'm just trying to give you a picture of as we get further and further out as we get further out of our tribe our family our order we're getting to things where the common ancestry with human goes further and further back in time the genetic similarities become more and more different and even just the physical differences if we look at it at a very superficial level become more and more and more different so you get to even a broader category this is where you get to the primates and this is probably something that you might be somewhat familiar from with and the term primates is general these animals that look like they either live in trees or rain forests or their descendant of things that live in trees so they have these things that they can grasp things with they're good at climbing broadly not all of them are humans are probably the worst primates when it comes to climbing or one of the worse but that's the general classification that we that's what we generally think of when we think of primates and if we think of a primate that is not a great ape you just have to think of a baboon so this right here is a baboon it is a primate but it is not a great ape it is probably a descendant some baboons do actually don't live in trees but all of them are probably descended from things that first live in trees and that's why their hands and their feet look the way they do now you get to even a broader level of classification you get to the mammals and once again probably something you're used to thinking about mammals are air-breathing animals and they tend to have fur or hair they tend to they tend to provide some form of milk for their young they have active mammary glands there's other things that we can talk about what makes a mammal I'm not going to go to the rigorous definition but just to give you an example of a mammal that is not a primate I could I could show you this polar bear right over here this is a mammal mammal that is not a mammal that is not a primate and I can do other things I could show you a tiger or I could show you a a giraffe or a horse and so I'm by no stretch of the imagination am I being comprehensive but let's keep getting broader now let's go now let's go to the class or where we're already at the class of Mammalia now let's go to the phylum and phylum we are humans and all mammals we are in the phylum chordates and chordates chordates we're actually we're actually within the sub phylum which I didn't write here vertebrates which means we have a vertebra we have a spinal column with a spinal cord in it coordinates are a little bit more general chordates is a phylum we're kind of the arrangement of where the mouth is where the digestive organs where the anus is where the where the spinal column is where the brains where the eyes where the mouth they're kind of all in the same place and if you think about it everything I've listed here kind of has the same general structure you have a spinal column you have a brain you have a mouth then the mouth leaves to some type of a digestive column and at the end of it you have an anus over there and you have eyes in front of the brain and so this is a general way and I'm not being very rigorous here is how you describe a chordate and to show a chordate that is not a mammal you would just have to think of fish or sharks so this right over here this right over here let me make sure let me this right over here is a is a non mammal cordate this is a great white shark over here now let's go even broader and you'll see now we're getting to things that are very very not very very not a human like so you go one step for broader now we're in Animalia where the kingdom of animals and this is the broadest definition that or the broadest category that carlin a is thought about well actually he did go into the into trees as well but when you think of a kingdom animals and you think of things that aren't chordates you start going into things like insects and you start going into things like jellyfish if you go even broader now we're talking about the domain you go to Eukarya so these are all organisms that have cells and inside those cells they have complex structures so if you fear you carry you have cells with complex structures if you're a pro carrier which you don't have complex structures inside your cell but other Eukarya that are not animals include things like include things like like plants and obviously I'm giving no justice to this whole branch of the Tree of Life I can it could be just as rich or richer than everything I've drawn over this is just a small fraction of the entire Tree of Life but let's go even broader than that so if you go even broader than that and you say well what's a kind of life-form that isn't eukaryote that wouldn't have these more complex cell structures these the mitochondria in the cells the the the cell nucleus is then you just have to think about something like bacteria and if you want to go even broader there's things like viruses that you can even debate whether they really even are life because they're dependent on other life-forms for X with their actual reproduction but they are they do have genetic material like everything else and that to me is kind of a mind-blowing idea as different as a plant is look it up house plant is in your house right now or the tree when you walk home or bacteria or this jellyfish there is a commonality that we all have DNA and that DNA for the most part replicates in a very very very similar way so it's actually crazy that we actually even are related that we even do have a common ancestor with some of these things and then it even begs the question well what about things like viruses anyway I'll leave you here and I really just want you to let you know that kind of make sure you realize that this is a a it's definitely worth studying because we we understand where we fit in and kind of the universe of living things but I also want to let you know that it is a little bit of an art on where you decide where to make these classifications where you decide to focus on whether you want to focus on you know what properties whether is how they reproduce or how they feed their young or can they move around or what they breathe or whatever things like that anyway I'll let you go there
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