Tree of life
Species What a species is and isn't. Ligers, tiglons, mule, hinnies, and dogs
⇐ Use this menu to view and help create subtitles for this video in many different languages.
You'll probably want to hide YouTube's captions if using these subtitles.
- 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 the living things around us, than all of the life that surrounds 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 as 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 things that look like it than it does to
- the grass behind it, or to that tree, and so we start saying oh maybe maybe I should group this thing
- right over here into a group with other things like it and that's the very most building block of how we
- classify all of the living things around us, is putting them into buckets called species. So for example,
- this is one particular animal, but we see other animals that seem to look like it so we say they're all
- a part of a species of lions, and this animal its one animal and there's other animals that have stripes
- but some might be fatter, or taller, or skinnier, or whatever else darker or lighter, but we say they're
- similar enough that we call them all, we call them all tigers. We call all the animals even though they
- might be a little bit bigger, skinnier, or fatter, lighter, or darker we call all of them that have this
- kind of, they look similar to this thing right over here we'd call this, 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 straight forward way to think about it. Oh everything that looks
- kind of like this character right here is a lion. Everything 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 or things that act like each other, because what we will see is that there are some things
- that could be very different, at least in how they look or act that are actually closely related, and
- then we will talk about what it means to be closely related, and then we can see things that look very
- similar, that they have similar structures, they have similar behavior like for example bats and birds
- but they're 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 a 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, and offspring are fertile. Which means that the offspring can then have have further have babies,
- that they're not, they're not sterile. 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 and a female lioness and most of the time they will be able to have offspring and the offspring
- can go and mate with other lions or lionesses depending on their sex, and then they can have viable offspring
- so it seems to work out pretty well for lions. 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 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, these are kind of fascinating animals. Their offspring is called a liger. You get
- a male lion breeding with the female tiger you produce a liger which is a hybrid a cross between a lion
- and a tiger, and they're fascinating animals actually larger than either lions or tigers. They're the
- largest cats that we know off, but these ligers cannot be referred to as a separate species, or you can't
- say 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 is not fertile. is not able to produce offspring. There have been
- one of stories of ligers being mated with either a lion or tiger but those are one off stories. In general
- ligers can't interbreed, and in general this combination isn't going to produce offspring that can keep
- interbreeding and are fertile. So that's why we say that lions and tigers are different species, and that
- ligers we wouldn't even call it 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 about 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 a tigloon actually don't know
- how to pronounce that and that is a a different hybrid that has slightly different properties than a liger.
- S o I encourage you to look up what a tiglon 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 donkeys. So not only a donkey interbreed
- with another donkey but 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 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 tiglon, we would consider
- them a hybrid. So these are all hybrids, what we would call a cross. In general the world hybrid is
- used when you have two things, two different types that are somehow coming together, somehow having a
- combination, and once again like the case with the tiglon 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 called a hinny which similarly 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 good properties of both donkeys and horses
- hinnys 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 of we just kind of tried to think oh well
- how can we classify things and we said well hey maybe things that look and act similar should be called
- species but i want to show you where maybe things that look and act different, we shouldn't call them
- species. I want to show you a very typical case one that is really all around us all the time where this
- definition animals that can interbreed and the offspring are fertile really does beseem 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. As I said this is a very typical species here because dogs and
- I just took a sample of different types of breeds of dogs they can look very very different. Its obvious
- look at the difference between these, for example this little chihuahua here and this dog right over
- here obviously they're size wise their look even the way they act are almost are much much more different much
- than maybe how this donkey would act relative to this horse or how this lion would act relative to this
- tigress and that they obviously look, they look very different. They're completely different sizes but
- these two things actually can interbreed although with these two in particular 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 most of this is really due to human
- doings trying to breed for particular, specific traits. Even though they look so different and act so
Be specific, and indicate a time in the video:
At 5:31, how is the moon large enough to block the sun? Isn't the sun way larger?
|
Have something that's not a question about this content? |
This discussion area is not meant for answering homework questions.
Discuss the site
For general discussions about Khan Academy, visit our Reddit discussion page.
Flag inappropriate posts
Here are posts to avoid making. If you do encounter them, flag them for attention from our Guardians.
abuse
- disrespectful or offensive
- an advertisement
not helpful
- low quality
- not about the video topic
- soliciting votes or seeking badges
- a homework question
- a duplicate answer
- repeatedly making the same post
wrong category
- a tip or feedback in Questions
- a question in Tips & Feedback
- an answer that should be its own question
about the site
Share a tip
Suggest a fix
Have something that's not a tip or feedback about this content?
This discussion area is not meant for answering homework questions.