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And they are connected at the centromere, not to be confused with a centrosome. And then here's the magenta, one of the magenta sister chromatids, and another one. And once again, it's not magenta in real life, I'm just making it in magenta because it looks nice. That's the centromere right over there. Our centrosomes ... | Mitosis Cells MCAT Khan Academy.mp3 |
That's the centromere right over there. Our centrosomes are at opposite ends of the cell at this point, at opposite ends of the cell. And you might have heard the word, let me label this again, I labeled it in a previous video. That's centrosomes. Centrosomes where the two sister chromatids are connected. That's a cent... | Mitosis Cells MCAT Khan Academy.mp3 |
That's centrosomes. Centrosomes where the two sister chromatids are connected. That's a centromere. Centromere. Now you might have heard the word centriole. Centrioles are actually, they help, they exist inside the centrosomes. They're these two kind of cylindrical looking structures. | Mitosis Cells MCAT Khan Academy.mp3 |
Centromere. Now you might have heard the word centriole. Centrioles are actually, they help, they exist inside the centrosomes. They're these two kind of cylindrical looking structures. Each of the centrosomes have two centrioles. But for the sake of this video, you could say, well the centrioles are just part of the c... | Mitosis Cells MCAT Khan Academy.mp3 |
They're these two kind of cylindrical looking structures. Each of the centrosomes have two centrioles. But for the sake of this video, you could say, well the centrioles are just part of the centrosomes. But I'm just listing you all the words that involve centri-something. Centrioles right over there. And you have two ... | Mitosis Cells MCAT Khan Academy.mp3 |
But I'm just listing you all the words that involve centri-something. Centrioles right over there. And you have two of them per centrosome. So hopefully that helps clarify some confusion. But these things line up. And a lot of what you're about to see, this orchestration, these things moving around in the cell, things ... | Mitosis Cells MCAT Khan Academy.mp3 |
So hopefully that helps clarify some confusion. But these things line up. And a lot of what you're about to see, this orchestration, these things moving around in the cell, things lining up and soon things pulling apart, these are all coordinated with actually a fairly sophisticated mechanism of kind of a scaffold of t... | Mitosis Cells MCAT Khan Academy.mp3 |
And the centrosomes role, until now I've just been kind of drawing them. You're like, well what do they do? Well the centrosomes role is these microtubules extend from them to each other and to the centromeres of these chromosomes. And to a large degree, although they're not the only actors here, they help pull and pus... | Mitosis Cells MCAT Khan Academy.mp3 |
And to a large degree, although they're not the only actors here, they help pull and push things in the right way. So these help make sure that the two centrosomes push away from each other. And then as we'll see in the next phase, that they're able to pull one of each of the sister chromatids from each of the pairs to... | Mitosis Cells MCAT Khan Academy.mp3 |
So this right over here where you see where the nuclear envelope is now gone, the chromosomes have been lined up just like this and your centrosomes are on opposite sides of your cell, we call this the metaphase. We call this the metaphase of mitosis. And then you can imagine what's going to happen next. What's going t... | Mitosis Cells MCAT Khan Academy.mp3 |
What's going to happen next? What's going to happen next is, and let me, I don't want to draw it too big because I want to be able to fit it all in one page. What's going to happen next is that those microtubules are going to start pulling on each of the sister chromatids. Let me draw that. So let me draw, so you have ... | Mitosis Cells MCAT Khan Academy.mp3 |
Let me draw that. So let me draw, so you have this centrosome right over here, you have all these microtubules in your cell. You have this centrosome right over here, all those microtubules, and this one is going to be pulling, is going to be getting one of the blue chromatids to pull towards it or to move towards it. ... | Mitosis Cells MCAT Khan Academy.mp3 |
So let me draw that. So this is one blue chromatid right over here. And this one is going to be pulling the other blue chromatid towards it. And same thing for the magenta. And same thing for the magenta. So that one's being pulled that way and this one is being pulled that way. And just in case you're concerned about ... | Mitosis Cells MCAT Khan Academy.mp3 |
And same thing for the magenta. And same thing for the magenta. So that one's being pulled that way and this one is being pulled that way. And just in case you're concerned about some more of the words, the vocabulary involved, the point at which these microtubules connect to what used to be sister chromatids, but now ... | Mitosis Cells MCAT Khan Academy.mp3 |
And just in case you're concerned about some more of the words, the vocabulary involved, the point at which these microtubules connect to what used to be sister chromatids, but now that they're apart, we now call them chromosomes. When they were merged, this was one chromosome and they have two sister chromatids. But n... | Mitosis Cells MCAT Khan Academy.mp3 |
So now you actually have four chromosomes over here. And this point right over here, we call a kinetochore. Kinetochore, and even exactly how that interface works and exactly how things move is not fully understood. Some of this stuff is understood, but some of this is still an area of research. So something even as ba... | Mitosis Cells MCAT Khan Academy.mp3 |
Some of this stuff is understood, but some of this is still an area of research. So something even as basic as cell division, not so basic after all. So this right over here where you can start to see the DNA kind of migrating to their respective sides of the cell, we call this the anaphase. We call this the anaphase. ... | Mitosis Cells MCAT Khan Academy.mp3 |
We call this the anaphase. And then that takes us to the last formal phase of mitosis, and that is called telophase. Telophase. And in telophase, let me do my best job to draw it. And you can already see I've started to draw that the cells, the cellular membrane's starting to pinch in kind of in preparation for cytokin... | Mitosis Cells MCAT Khan Academy.mp3 |
And in telophase, let me do my best job to draw it. And you can already see I've started to draw that the cells, the cellular membrane's starting to pinch in kind of in preparation for cytokinesis, in preparation for the cell splitting into two cells. So I'll do it a little bit more. Cytokinesis is usually described as... | Mitosis Cells MCAT Khan Academy.mp3 |
Cytokinesis is usually described as kind of being a separate process than mitosis, although it is obviously they are, they kind of together help the cell fully turn into two cells. So now in telophase, so you have this, what used to be a sister chromatid, now we could call it a chromosome on its own. And we have this c... | Mitosis Cells MCAT Khan Academy.mp3 |
And we have, and we have this chromosome right over there, let me actually do it on both sides. So you have there, and you have, you have this right over here. And actually, let me draw it a little bit different. Because at this phase, you're really starting to unwind what happened at prophase. So prophase, you have th... | Mitosis Cells MCAT Khan Academy.mp3 |
Because at this phase, you're really starting to unwind what happened at prophase. So prophase, you have the disappearance of the nuclear membrane, and you have the condensation of the chromosomes into this form here. Telophase, that's unwinding a little bit. So actually let me draw the two centrosomes. So you have one... | Mitosis Cells MCAT Khan Academy.mp3 |
So actually let me draw the two centrosomes. So you have one centrosome, do that same color that I had before. So you have one centrosome right here, you have another centrosome right over there. And now the DNA, this blue DNA, this chromosome's now here, but it's starting to get a little, underwound a little bit. Same... | Mitosis Cells MCAT Khan Academy.mp3 |
And now the DNA, this blue DNA, this chromosome's now here, but it's starting to get a little, underwound a little bit. Same thing on this side right over here. Magenta chromosome is on here, but once again, it's starting to get a little bit unwound. Same thing over here. And you start to have nuclear membranes forming... | Mitosis Cells MCAT Khan Academy.mp3 |
Same thing over here. And you start to have nuclear membranes forming around the DNA. So once again, it's kind of redoing what was undone in prophase. Undone in prophase. And so when you're done, you essentially, you're gonna have these nuclear membranes, the DNA is gonna go back to its chromatin form, and then you hav... | Mitosis Cells MCAT Khan Academy.mp3 |
Undone in prophase. And so when you're done, you essentially, you're gonna have these nuclear membranes, the DNA is gonna go back to its chromatin form, and then you have cytokinesis. And cytokinesis is the process by which this gets fully pinched together, and you have two separate cells. And some folks will say, oh, ... | Mitosis Cells MCAT Khan Academy.mp3 |
And some folks will say, oh, it kind of begins in anaphase, and it finishes after telophase, but it's kind of happening near the end of mitosis, in parallel with it. So this is cytokinesis. Cytokinesis. Cytokinesis right over here. This essentially is how this larger cell that had two nuclei, how this divides, fully di... | Mitosis Cells MCAT Khan Academy.mp3 |
Cytokinesis right over here. This essentially is how this larger cell that had two nuclei, how this divides, fully divides into two cells. And at that point, you're back to, you're back to this phase of the cell cycle. Now each of these, now two cells, are going to go through interphase. G1, S phase, replicate their DN... | Mitosis Cells MCAT Khan Academy.mp3 |
And to say that the genes and the environment are both important is really true, but really more specifically, they interact. And so I've alluded to this previously with the tea and the hot water example, but I want to get really specific with the language here, because not only do our genes and our environment both af... | Gene environment interaction Behavior MCAT Khan Academy.mp3 |
One we'll say is genetically predisposed to be much more attractive than the other one. So we have this attractive baby, and we have this really hideous baby, and as a result, the beautiful baby over here, it receives more affection and more attention, and it grows up to be generally more sociable and well-adjusted. Bu... | Gene environment interaction Behavior MCAT Khan Academy.mp3 |
As we've learned, the environment activates those genes, so in this case, maybe the genes are activated by environmental stressors. So both babies have these genes, but throughout life, this cute and ultra-lovable baby is surrounded by this great and supportive network, and it has reduced stress, so its genes aren't st... | Gene environment interaction Behavior MCAT Khan Academy.mp3 |
And maybe that's because this baby is getting made fun of all the time, or maybe it's because it just has less friends. So I guess the cute baby's genes are somewhat responsible for setting up the environment, but really also the environment is responsible, at least to some degree, in keeping those depression genes at ... | Gene environment interaction Behavior MCAT Khan Academy.mp3 |
So this is kind of a crude example of gene and environment interacting with each other, but a more specific example is the genetic condition PKU, or phenylketonuria. So P-K-U. And phenylketonuria is a genetic condition in humans that's caused by mutations to a gene that code for a liver enzyme. And that liver enzyme is... | Gene environment interaction Behavior MCAT Khan Academy.mp3 |
And that liver enzyme is phenylalanine hydroxylase, so PAH. But because the enzyme is missing the amino acid phenylalanine, it doesn't get converted into the amino acid tyrosine during one of the metabolic pathways in our body. And so this causes a buildup of phenylalanine in the body, which can cause problems for brai... | Gene environment interaction Behavior MCAT Khan Academy.mp3 |
So PKU, it affects one in about 15,000 babies in the U.S., but most of these babies grow up without any major problems. And it turns out that during infant screening, these babies are identified and they're placed on a special phenylalanine-free diet. So because they're not taking in all of this phenylalanine, it's res... | Gene environment interaction Behavior MCAT Khan Academy.mp3 |
And whenever we hear this word, I mean, even if we don't hear it in the biological context, we imagine that something is changing. It is evolving. And so when people use the word evolution in our everyday context, they think of this notion of change, that this is going to test my drawing ability. But you see an ape, bu... | Introduction to Evolution and Natural Selection.mp3 |
But you see an ape, bunt over. We've all seen this picture at the Natural Museum, and he's walking hunchback like that, and his head's bent down. And I'm doing my best. That's the ape. Maybe he's also wearing a hat. And then they show this picture where he slowly, slowly becomes more and more upright. And eventually, h... | Introduction to Evolution and Natural Selection.mp3 |
That's the ape. Maybe he's also wearing a hat. And then they show this picture where he slowly, slowly becomes more and more upright. And eventually, he turns into some dude who's just walking on his way to work, also just as happy. And now he's walking completely upright. And it's some kind of implication that walking... | Introduction to Evolution and Natural Selection.mp3 |
And eventually, he turns into some dude who's just walking on his way to work, also just as happy. And now he's walking completely upright. And it's some kind of implication that walking upright is better than not walking upright, et cetera, et cetera. Oh, he doesn't have a tail anymore. Let me eliminate that. This guy... | Introduction to Evolution and Natural Selection.mp3 |
Oh, he doesn't have a tail anymore. Let me eliminate that. This guy does have a tail. Let me do it in an appropriate width. This guy has a tail, so you're going to have to excuse my drawing skills. But we've all seen this. If you've ever gone to a natural history museum, they'll just make more and more upright apes. | Introduction to Evolution and Natural Selection.mp3 |
Let me do it in an appropriate width. This guy has a tail, so you're going to have to excuse my drawing skills. But we've all seen this. If you've ever gone to a natural history museum, they'll just make more and more upright apes. And eventually, you get to a human being. And it's this idea that the apes somehow chang... | Introduction to Evolution and Natural Selection.mp3 |
If you've ever gone to a natural history museum, they'll just make more and more upright apes. And eventually, you get to a human being. And it's this idea that the apes somehow changed into a human being. And I've seen this in multiple contexts, even inside of biology classes and even the scientific community. They'll... | Introduction to Evolution and Natural Selection.mp3 |
And I've seen this in multiple contexts, even inside of biology classes and even the scientific community. They'll say, oh, the ape evolved into the human, or the ape evolved into the pre-human, the guy that almost stood upright. The guy that was a little bit hunched back, so he looked a little bit like an ape and a li... | Introduction to Evolution and Natural Selection.mp3 |
And I want to be very clear here. Even though this process did happen, that you did have creatures that over time accumulated changes that maybe their ancestors might have looked more like this, and eventually they looked more like this, there was no active process going on called evolution. It's not like the ape said,... | Introduction to Evolution and Natural Selection.mp3 |
And it's not like the DNA knew. The DNA didn't say, hey, it is better to be walking than to be kind of hunched back like an ape, and so therefore, I am going to try to somehow spontaneously change into this dude. That's not what evolution is. It's not like some people imagine that maybe there's a tree, and on that tree... | Introduction to Evolution and Natural Selection.mp3 |
It's not like some people imagine that maybe there's a tree, and on that tree there's a bunch of good fruit at the top of the tree. Maybe they're apples. And then maybe you have some type of cow-like creature, or maybe it's some type of horse-like creature that says, gee, I would like to get to those apples. And that j... | Introduction to Evolution and Natural Selection.mp3 |
And that just because they want to get there, maybe the next generation, they keep trying to raise their neck. And then after generation after generation, their necks get longer and longer, and eventually they turn into giraffes. That is not what evolution is, and that's not what it implies. Although sometimes the ever... | Introduction to Evolution and Natural Selection.mp3 |
Although sometimes the everyday notion of the word seems to make us think that way. What evolution is, and actually this is the word that I prefer to use, it's natural selection. Natural selection, let me write that word down. And literally what it means is that in any population of living organisms, you're going to ha... | Introduction to Evolution and Natural Selection.mp3 |
And literally what it means is that in any population of living organisms, you're going to have some variation. And this is an important key word here. Variation just means, look, there's just some change. If you look at the kids in your school, you'll see variation. Some people are tall, some people are short, some pe... | Introduction to Evolution and Natural Selection.mp3 |
If you look at the kids in your school, you'll see variation. Some people are tall, some people are short, some people have blonde hair, some people have black hair, so on and so forth. There's always variation. And what natural selection is, is this process that sometimes environmental factors will select for certain ... | Introduction to Evolution and Natural Selection.mp3 |
And what natural selection is, is this process that sometimes environmental factors will select for certain variations. Some variations might not matter at all, but some variations matter a lot. One example that's given in every biology book, but it really is interesting. I believe they're called the peppered moth, and... | Introduction to Evolution and Natural Selection.mp3 |
I believe they're called the peppered moth, and this was pre-industrial revolution England. Most peppered moths, there was just this variation. Some of them were, I guess we could call them more peppered than others. So some of them might look like this. So it had spots like that. Some of them might have looked more li... | Introduction to Evolution and Natural Selection.mp3 |
So some of them might look like this. So it had spots like that. Some of them might have looked more like that. And of course, they had some black spots on them. And then some of them might have been, you know, just barely have any spots. You just have this natural variation. Like you'd see in any population of animals... | Introduction to Evolution and Natural Selection.mp3 |
And of course, they had some black spots on them. And then some of them might have been, you know, just barely have any spots. You just have this natural variation. Like you'd see in any population of animals, you'll see some variation in colors. Now, they were all happy probably for thousands of years, just this natur... | Introduction to Evolution and Natural Selection.mp3 |
Like you'd see in any population of animals, you'll see some variation in colors. Now, they were all happy probably for thousands of years, just this natural variation. It was a non-important trait for these peppered moths. But then all of a sudden, the Industrial Revolution happens in England, and all this soot gets r... | Introduction to Evolution and Natural Selection.mp3 |
But then all of a sudden, the Industrial Revolution happens in England, and all this soot gets released from all of these factories that are running these steam engines powered by coal. And so all of a sudden, a lot of the things that once were gray or white, for example, maybe some tree trunks. Let me draw some tree t... | Introduction to Evolution and Natural Selection.mp3 |
Maybe there were some tree trunks that used to look like this. Maybe some tree trunks used to look something like this. And a peppered moth would be pretty OK. And maybe there were some tree trunks that were pretty dark. But all of a sudden, the Industrial Revolution happens. Everything gets covered with soot from the ... | Introduction to Evolution and Natural Selection.mp3 |
But all of a sudden, the Industrial Revolution happens. Everything gets covered with soot from the coal being burned. And then all of a sudden, all the trees look like this. They're just completely pitch black, or they're a lot darker than they were before. Now, all of a sudden, you've had a major change to these moths... | Introduction to Evolution and Natural Selection.mp3 |
They're just completely pitch black, or they're a lot darker than they were before. Now, all of a sudden, you've had a major change to these moths' environment. And you have to think, what is going to select for these moths? Well, one thing that might get these moths are birds and the ability of the birds to see the mo... | Introduction to Evolution and Natural Selection.mp3 |
Well, one thing that might get these moths are birds and the ability of the birds to see the moths. So all of a sudden, if the environment became a lot blacker than it was before, you can guess what's going to happen. The birds are going to see this dude a lot easier than they're going to see this dude. Because this du... | Introduction to Evolution and Natural Selection.mp3 |
Because this dude on a black background, he's going to be a lot harder to see. And it's not like the birds won't catch this guy. They'll catch all of them. But they're going to catch this guy a lot more frequently. So you can imagine what happens. If the birds start catching these guys before they can reproduce, or may... | Introduction to Evolution and Natural Selection.mp3 |
But they're going to catch this guy a lot more frequently. So you can imagine what happens. If the birds start catching these guys before they can reproduce, or maybe while they're reproducing, what's going to happen? This guy, the darker dudes, are going to reproduce a lot more often. And all of a sudden, you're going... | Introduction to Evolution and Natural Selection.mp3 |
This guy, the darker dudes, are going to reproduce a lot more often. And all of a sudden, you're going to have a lot more moths that look like this. You're going to have a lot more of these dudes. So what happened here? Was there any design, or was there any active change by any of the moths? I mean, it looks like a re... | Introduction to Evolution and Natural Selection.mp3 |
So what happened here? Was there any design, or was there any active change by any of the moths? I mean, it looks like a really smart thing to do, to become black, right? Your surrounding became black, and you wait a couple of generations of these moths, and now all of a sudden, the moths are black. And you might say, ... | Introduction to Evolution and Natural Selection.mp3 |
Your surrounding became black, and you wait a couple of generations of these moths, and now all of a sudden, the moths are black. And you might say, wow, those moths are geniuses. They all somehow decided to evolve into black moths in order to hide from the birds more easily. But that's not what happened. You had a lot... | Introduction to Evolution and Natural Selection.mp3 |
But that's not what happened. You had a lot of variation in your peppered moth population. And what happened was that when everything turned darker and darker, these dudes right here, or dudettes, had a lot less success in reproducing. These guys just reproduced more and more and more. And these guys got eaten up befor... | Introduction to Evolution and Natural Selection.mp3 |
These guys just reproduced more and more and more. And these guys got eaten up before they were able to do, so maybe while they were reproducing, so that they couldn't produce as many offspring. And then this trait just became dominant. And then the peppered moth just became, you can kind of view it as a black moth. No... | Introduction to Evolution and Natural Selection.mp3 |
And then the peppered moth just became, you can kind of view it as a black moth. Now you might say, OK, Sal, that's one example. I need more. This is natural selection. It's purported to apply to everything. It purports to explain why we evolved from basic bacteria, or maybe even self-replicating RNA, which I will talk... | Introduction to Evolution and Natural Selection.mp3 |
This is natural selection. It's purported to apply to everything. It purports to explain why we evolved from basic bacteria, or maybe even self-replicating RNA, which I will talk about more in the future. I need more evidence of this. I need to see it in real time. And the best example of this is really the flu. And I'... | Introduction to Evolution and Natural Selection.mp3 |
I need more evidence of this. I need to see it in real time. And the best example of this is really the flu. And I'll do other videos in the future on what viruses are and how they replicate. And viruses are actually fascinating, because it's not even clear that they're alive. They're literally just little buckets of D... | Introduction to Evolution and Natural Selection.mp3 |
And I'll do other videos in the future on what viruses are and how they replicate. And viruses are actually fascinating, because it's not even clear that they're alive. They're literally just little buckets of DNA and sometimes RNA, which we'll learn is genetic information. And they're just contained in these viral, th... | Introduction to Evolution and Natural Selection.mp3 |
And they're just contained in these viral, these little protein containers that are these neat geometrical shapes. And that's all they are. They really don't have, you know, they're not like regular living organisms that actively move and that actively have metabolisms and all that. What they do is they take that littl... | Introduction to Evolution and Natural Selection.mp3 |
What they do is they take that little DNA and they inject it into other things that can process it. And then they use that DNA to produce more viruses. But anyway, we could do a whole series of videos on viruses. But the flu is a virus. And what happens every year is you have a certain type of virus and they have some ... | Introduction to Evolution and Natural Selection.mp3 |
But the flu is a virus. And what happens every year is you have a certain type of virus and they have some variation. And I'll just make the variation by, I don't know, how many dots they have. And they infect, let's say it's a human flu, they infect humans, and slowly our immune systems, which we can make a whole set ... | Introduction to Evolution and Natural Selection.mp3 |
And they infect, let's say it's a human flu, they infect humans, and slowly our immune systems, which we can make a whole set of videos on as well, start to recognize the virus and are able to attack them before they can do a lot of damage. So now you can imagine what happens if, let's say that this is the current flu.... | Introduction to Evolution and Natural Selection.mp3 |
They all have these little two dots and that's how, and we'll talk in the future what these dots are and how they can be recognized, but let's say that's how our immune system recognize them. They start realizing, oh, any time I get this little green dude with two dots on it, that's not a good thing to have around, so ... | Introduction to Evolution and Natural Selection.mp3 |
But flu, you can kind of think of them as being tricky, but they're not really tricky. They're not sentient objects, but what they do do is they constantly change. So what you have is, in any flu population, you're always having a little bit of change. So maybe the great majority of them have those two dots, but maybe ... | Introduction to Evolution and Natural Selection.mp3 |
So maybe the great majority of them have those two dots, but maybe every now and then one of them has one dot, one of them has three dots, and maybe that's just a random mutation. This just randomly happened. Maybe one in every million of these viruses have this only one dot instead of two dots. But what's going to hap... | Introduction to Evolution and Natural Selection.mp3 |
But what's going to happen as soon as, let's say, the human immune system gets used to attacking the virus with the two red dots? Well, then this guy isn't going to have to compete with the other virus capsules for infecting people. He's going to have people's DNA all to himself. And so he or she or whatever you want t... | Introduction to Evolution and Natural Selection.mp3 |
And so he or she or whatever you want to call this virus is then going to be more successful. So by next year's flu season, when people start sneezing and are able to spread it on doorknobs and whatever else again, this guy is going to be the new flu virus. So when you see this process of every year there's a new flu v... | Introduction to Evolution and Natural Selection.mp3 |
It is happening. It isn't this thing that only happens over eons and eons of time, although most of the substantial things that we see in our lives or even ourselves are based on these things that happened over eons and eons of time. But it happens on a yearly basis. Another example is if you think about antibiotics an... | Introduction to Evolution and Natural Selection.mp3 |
Another example is if you think about antibiotics and bacteria. Bacteria are these little cells that move around. And we'll talk more about them. They actually are definitely living. They have metabolisms and whatever else. And this is just a nice note. When people talk about infections, it could either be a viral infe... | Introduction to Evolution and Natural Selection.mp3 |
They actually are definitely living. They have metabolisms and whatever else. And this is just a nice note. When people talk about infections, it could either be a viral infection, which are these things that go and infect your DNA and then use your cell mechanisms to reproduce. Or it could be a bacterial infection, wh... | Introduction to Evolution and Natural Selection.mp3 |
When people talk about infections, it could either be a viral infection, which are these things that go and infect your DNA and then use your cell mechanisms to reproduce. Or it could be a bacterial infection, which are literally little cells that move around and they release toxins that make you sick and whatever else... | Introduction to Evolution and Natural Selection.mp3 |
They attack bacteria. They kill them. Now, you probably, if you know a couple of doctors or whatever, and you say, hey, I'm sick. I think I have a bacterial infection. Give me some antibiotics. A responsible doctor says, no, I won't give you antibiotics just willy-nilly, because what happens is the more antibiotics you... | Introduction to Evolution and Natural Selection.mp3 |
I think I have a bacterial infection. Give me some antibiotics. A responsible doctor says, no, I won't give you antibiotics just willy-nilly, because what happens is the more antibiotics you use, you're more likely to create versions and I want to be very careful about the word create, because you're not actively creat... | Introduction to Evolution and Natural Selection.mp3 |
But let's say, and let me finish my sentence, you're very likely to help select for antibiotic-resistant bacterias. Now, how does that work? So let's say that these are all bacteria and you have gazillions of them, right? And every now and then you get one that's slightly different. Now, in a population of bacteria, th... | Introduction to Evolution and Natural Selection.mp3 |
And every now and then you get one that's slightly different. Now, in a population of bacteria, these all will make you equally sick, and this is just some random difference in the bacteria, maybe on its DNA some slight different changes happened, but whatever happened. These all are the kind of bacteria, you don't wan... | Introduction to Evolution and Natural Selection.mp3 |
Your immune system can attack them and fight them off, but if you get a lot of them, they might kill you or make you sick or whatever else. Now, if everyone just starts using antibiotics when they're not sick or when they don't really need to in a life or death situation, you might have an antibiotic that is really goo... | Introduction to Evolution and Natural Selection.mp3 |
Well, now the blue bacteria have the whole ecosystem that before it was competing with all these green dudes to get all the good stuff inside of your body, but now he's all alone, and now he can replicate willy-nilly. So now he's going to replicate willy-nilly. And this is, once again, it wasn't like there was any desi... | Introduction to Evolution and Natural Selection.mp3 |
No. There's just these random changes that happen, and mutations and viruses and bacteria happen frequently. And there are these random changes that happen. And this might be a one in a billion change. But all of a sudden, if you start killing off all of the people that it's competing with, this guy can start replicati... | Introduction to Evolution and Natural Selection.mp3 |
And this might be a one in a billion change. But all of a sudden, if you start killing off all of the people that it's competing with, this guy can start replicating really fast and then become the dominant bacteria. And then all of a sudden, that antibiotic that you had developed very carefully to destroy the green du... | Introduction to Evolution and Natural Selection.mp3 |
And you have this superbug. You might have heard the word superbug. That's what a superbug is. It's not like it designed itself somehow. It's just that we got very good at killing its competition, and so we allowed it to take over. And we can't kill it because all of the drugs were just good at killing its competition.... | Introduction to Evolution and Natural Selection.mp3 |
It's not like it designed itself somehow. It's just that we got very good at killing its competition, and so we allowed it to take over. And we can't kill it because all of the drugs were just good at killing its competition. That these bacteria just keep mutating and keep mutating. And if we use these antibiotics a li... | Introduction to Evolution and Natural Selection.mp3 |
That these bacteria just keep mutating and keep mutating. And if we use these antibiotics a little bit too heavily, we'll always be selecting for the things that won't be affected by the antibiotics. Well, anyway, I think I've spoken long enough. But this is a fascinating, fascinating topic. And I really wanted to make... | Introduction to Evolution and Natural Selection.mp3 |
But this is a fascinating, fascinating topic. And I really wanted to make this my very first video or lecture, if you will, on biology. Because if you really went to, you know, biology is the study of life, and we can talk about what life is, whether viruses are living, whatnot. But if you really want to study living s... | Introduction to Evolution and Natural Selection.mp3 |
But if you really want to study living systems, you really can't make any assumptions other than natural selection. We could go to another planet where the creatures don't have DNA. Or maybe they have some other type of hereditary information stored in their cells. Or they replicate some other way. Or they're not even ... | Introduction to Evolution and Natural Selection.mp3 |
Or they replicate some other way. Or they're not even carbon-based. Maybe they're silicon-based. And if we went to that type of a planet in order to study the biology on that planet, everything else we know about biology, about viruses and DNA, would be useless. But if we do understand this one concept of natural selec... | Introduction to Evolution and Natural Selection.mp3 |
And if we went to that type of a planet in order to study the biology on that planet, everything else we know about biology, about viruses and DNA, would be useless. But if we do understand this one concept of natural selection, that your environment will select. And there's no active process here. It's just random stu... | Introduction to Evolution and Natural Selection.mp3 |
And there's a couple of ways to tackle it. The first way is, well, let's figure out the surface area of the sides that we can see and then think about what the surface area of the sides that we can't see are and how they might relate and then add them all together. So let's do that. So the front of the box is 20 centim... | Surface area of a box.mp3 |
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