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Video transcript

we humans like to get our heads around all of the complexity around us by classifying things and you can imagine there's no more obvious thing to classify than all of the living things around us then all of the life that arounds us so what I want to start talking about is how do we classify all of the life around us and this is more often generally referred to taxonomy but the most basic question you have when you look at all of the life around you you start to see similarities between some of these living things you see obviously this this this thing right over here is more similar to the the things that look like it than it does to the grass behind it or to that tree and so we start saying well maybe maybe I should group this thing right over here into a group with other things like it and that most build at that very most building block of how we classify all of the living things around us is putting them into buckets called species called species so for example this is one particular animal but we see other animals that seem to look like it and so we say they're all part of the species of lions and this animal it's one animal and there's other animals that have stripes but some might be fatter or taller or skinny or whatever else darker or lighter but we say they're similar enough but we call them all we call them all tigers we call all the animals even though they might be a little bit bigger or skinny or fat or lighter or darker we call all of them that have this kind of they look similar to this thing right over here we would call this we would call this a donkey we would call this a donkey we would call the things that we think are like this animal right here a horse now that might seem like a straight pretty straightforward way to think about it Oh everything that looks kind of like this character right here is a line anything that looks kind of like this character right here is a tiger but that by itself is not a good enough definition for species things that look like each other are things that act like each other because what we'll see is that there's some things that could be very different at least in how they look or act but are actually closely related and we'll talk about it what it means to be closely related and then we can see things that look very similar that they have similar structures or they have similar behavior like for example bats and birds but they are actually all very very distantly related so we need a more exact definition for species than just things that look like each other or just things that act like each other and so the most typical definition for species are animals animals that can interbreed that can interbreed interbreed and when we say interbreed literally they can produce offspring with each other and and the offspring are fertile the offspring are fertile which means that the offspring can then have have further have babies that they're not they're not sterile that they that they're capable of breeding with other animals and producing and producing more offspring and to show an example of this this right here is a male lion you find a male lion and a female lioness and most of the time they will be able to have offspring and those offspring can go and mate with other lines or lionesses depending on their sex and then they can have viable offspring so it seems to work out pretty well for lines same thing is true of tigers now it does turn out that if you get a male lion if you have a male lion and a female tigress female tigress they can breed they can breed and they can produce offspring and their offspring which was made famous by Napoleon Dynamite he was kind of fascinated by these are kind of fascinating animals their offspring is called a liger you get a male lion breeding with a female tiger you produce a liger which is a hybrid ASIC cross between a lion and a tiger and they're fascinating animals actually larger than either lions or Tigers are the largest cats that we know of but these laggers cannot be referred to as a separate species or you can't say that mitt that lions and tigers are the same species because even though they are able to interbreed their offspring for the most part is not able to put is not fertile it's not able to produce offspring there have been one-off stories about ligers being mated with either a lion or tiger but the or one-off stories in general ligers can't invert interbreed and in general these this this combination isn't going to produce offspring that can keep interbreeding or that our fertile so that's why we say that lions and tigers are different species and that liger we wouldn't even call it as a species at all we would actually call it a hybrid between two species now the same thing is true and actually you might be asking yourself well this was a male lion and a female tigress what if we went the other way around what if we had a female lioness and a male tiger in that case you would produce something else called a tiglon or tag LAN actually don't know how to pronounce that and that is a different hybrid that has slightly different properties than a liger so tiger I encourage you to look up what a Tai Glahn is similarly you give me a male donkey you give me a male donkey and donkeys are clearly a species by themselves because if you give me a male donkey and a female donkey they can reproduce produce another donkey and then that donkey can mate with other donkeys to produce more and more donkeys so not only can a donkey in to read with another donkey but that that that product that child donkey can then interbreed with can keep interbreeding with other donkeys similarly horses they can interbreed and produce fertile offspring but if you give me a male donkey and a female horse and a female horse they can mate and they can produce a mule they can produce a mule but once again like the ligers mules are not at least as far as I know mules cannot they're not fertile mules cannot produce further offspring they cannot interbreed with each other and because even though donkeys and horses can breed and produce mules their offspring aren't fertile we don't consider donkeys and horses part of the same species and we would consider mules like a liger or a tag line we would consider them a hybrid so these are all hybrids or we would call cross in general the word hybrid is used when you have two things of two different types that are somehow coming together somehow having a combination and once again like the case with the tag line you might say well what if I had a female donkey what if I had a female donkey and a male horse and then you would actually produce something called a hinny like a called a hinny which similarly which isn't as common as a mule and people like to use mules they're actually very good work animals because they they have some of the good properties of both donkeys and horses hinnies are less common but once again it is possible and they have different properties than mules and I do want to emphasize this idea because when we started off we just kind of try to think about well how can we classify things and we said hey maybe things that look and act similar we can call a species but I want to show you where or and maybe things that looking act different we shouldn't call them species but I want to show you a very typical case and one that's really all around us all the time where this definition animals that can interbreed and the offspring are fertile really does be seemed to become much much more important than just some notion of animals that look alike or animals that act the same and the best example of that is with dogs and I said this is a very typical species here because dogs and I just took a sample of some of the different types of breeds of dogs they can look very very different it's obvious look at look at the difference between these dogs these for example this little chihuahua here and this dog right over here obviously their size wise they look and even how they act are almost are much much more different than maybe how this donkey would act relative to this horse or how this line would act relative to this tigress and they obviously look look they look very different they have completely different sizes but these two things actually can interbreed although for these two in particular it seems like the mechanics would get kind of difficult but assuming they get over the mechanical hurdles they could interbreed and produce fertile offspring same for these two characters same for these two characters over here and because of that even though all the different breeds of dogs and all most of this is really due to humans doings of trying to breed for specific traits even though they look so different and even though they act so different because they can interbreed and they can produce fertile offspring we consider all of these things to be members of the same species
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