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And it's called the Boveri-Sutton chromosome theory of inheritance, because right around the same time, they both started to realize that maybe chromosomes were the actual molecular mechanism, the cellular mechanism by which these factors segregate and independently assort. And so this is, let me write this down, this ... | Boveri-Sutton Chromosome Theory.mp3 |
And even though they're starting to say maybe chromosomes have something to do with it, they still don't know exactly what is inside the chromosomes that are allowing somehow this information to be encoded. And we'll get to that, and we will get to that in a little bit. But let me just underline this, Boveri-Sutton chr... | Boveri-Sutton Chromosome Theory.mp3 |
And so what was their key insight? Well, they started to look inside of cells. Meiosis was observed actually after Mendel published his laws of inheritance. And then chromosomes, or how chromosomes behave in meiosis were discovered after that. And then these guys, they independently studied different organisms. Walter ... | Boveri-Sutton Chromosome Theory.mp3 |
And then chromosomes, or how chromosomes behave in meiosis were discovered after that. And then these guys, they independently studied different organisms. Walter Sutton, he studied grasshoppers. Theodore Boveri, he studied sea urchins. But they looked at meiosis, and they looked at the reproduction and the fertilizati... | Boveri-Sutton Chromosome Theory.mp3 |
Theodore Boveri, he studied sea urchins. But they looked at meiosis, and they looked at the reproduction and the fertilization during these processes, and they saw that the chromosomes seemed to do things that were very similar to these laws of segregation, laws of independent assortment, laws of dominance. And actuall... | Boveri-Sutton Chromosome Theory.mp3 |
But he saw that, let's say that you had an organism here, and in this particular organism, I just did it for simplification, it has two pairs of homologous chromosomes. So what does homologous chromosomes mean? Well, these two are different chromosomes, but they seem to be very similar. It seems like they're kind of th... | Boveri-Sutton Chromosome Theory.mp3 |
It seems like they're kind of the same length, same size, same shape. So that's one pair of homologous chromosomes. That's another pair of homologous chromosomes. So notice, homologous chromosomes, two things that are kind of looking the same, but maybe they're a little bit different, we're not sure. Well, maybe this i... | Boveri-Sutton Chromosome Theory.mp3 |
So notice, homologous chromosomes, two things that are kind of looking the same, but maybe they're a little bit different, we're not sure. Well, maybe this is what fits what's going on right over here with these factors. Maybe, just maybe, maybe one of these chromosomes somehow has on it someplace what encodes for the ... | Boveri-Sutton Chromosome Theory.mp3 |
Now this is starting to make sense because they would be homologous chromosomes, similar, the chromosomes look like they code for the same thing, for the same factors, for the same genes, but there might be some variation between these chromosomes. And these guys weren't, you know, they weren't able to somehow sequence... | Boveri-Sutton Chromosome Theory.mp3 |
For example, this capital A one, it'll replicate, so you have capital A, but then, and then this is the lowercase a one right over here, you might have some crossover, and we'll talk about that when you, you can review meiosis if that looks unfamiliar. But then they segregate. You could have your capital A ones right o... | Boveri-Sutton Chromosome Theory.mp3 |
And they independently sort from the other chromosomes. So this one right over here might be the capital B, this might be the lowercase b. And whether or not this gets a, whether or not this gets a capital B or a lowercase b is independent of whether it got a capital A or a lowercase a. So it seems like these chromosom... | Boveri-Sutton Chromosome Theory.mp3 |
So it seems like these chromosomes independently sort. And so they came up with this chromosomal theory that it looks like maybe chromosomes are what contain these heritable factors that Mendel was talking about, because it seems like chromosomes behave very similar to those heritable factors. Maybe chromosomes code fo... | Boveri-Sutton Chromosome Theory.mp3 |
And as we know now, they were right. So this was a very, very big deal. But it's important to realize that they weren't sure. They established the theory, they were able to make some observations with the grasshoppers and the sea urchins, and they saw the patterns between what Mendel was describing and the way chromoso... | Boveri-Sutton Chromosome Theory.mp3 |
They established the theory, they were able to make some observations with the grasshoppers and the sea urchins, and they saw the patterns between what Mendel was describing and the way chromosomes behave during meiosis. And then they know that each of these products of meiosis, each of these gametes, will then go and ... | Boveri-Sutton Chromosome Theory.mp3 |
Today I'm going to give you a quick introduction into genetic mutations. But first, let's go over the central dogma of molecular biology, which is just the idea that genetic information in a cell is stored in the form of DNA. And this DNA is used to generate complementary RNA through a process called transcription. Tha... | An introduction to genetic mutations Biomolecules MCAT Khan Academy.mp3 |
That RNA is then used to synthesize a corresponding protein through the process of translation. So looking at a quick example, our short DNA strand here will be used to generate an RNA strand. Remember that A pairs with U, or T, and C pairs with G. Next, our RNA will be used to generate protein through translation. And... | An introduction to genetic mutations Biomolecules MCAT Khan Academy.mp3 |
And remember that during this process, RNA nucleotides are read in groups of three, called codons, in order to generate corresponding amino acids. Now, just very generally, we say that mutations have the effect of making this synthesized protein not turn out quite right. So I'm going to give a quick shout-out to sickle... | An introduction to genetic mutations Biomolecules MCAT Khan Academy.mp3 |
So you may remember that there is a protein in red blood cells called hemoglobin, which we can also call Hb. And hemoglobin is a protein that coordinates to iron ions in order to hold onto oxygen molecules and transport them throughout the body. Now, the mutation that causes sickle cell disease results in a mutated for... | An introduction to genetic mutations Biomolecules MCAT Khan Academy.mp3 |
And the difference between normal hemoglobin and HbS is that one glutamate amino acid residue is being replaced with a valine amino acid residue. And this small change results in all of these mutated HbS proteins aggregating together in a red blood cell, which makes it very difficult for that red blood cell to transpor... | An introduction to genetic mutations Biomolecules MCAT Khan Academy.mp3 |
So where are mutations found, and how did they come up in the first place? Well, let's look at a couple of different possible mistakes that could lead to an incorrectly produced protein. So first, we'll see what happens if a cell makes a mistake during translation. And we'll stick with our example of sickle cell diseas... | An introduction to genetic mutations Biomolecules MCAT Khan Academy.mp3 |
And we'll stick with our example of sickle cell disease from before. So let's say that we have this sample piece of DNA with three nucleotides from the gene coding for hemoglobin. This DNA is transcribed to form the complementary RNA sequence GAG. Now, that GAG would normally correspond to a glutamate residue during tr... | An introduction to genetic mutations Biomolecules MCAT Khan Academy.mp3 |
Now, that GAG would normally correspond to a glutamate residue during translation. But a mistake during translation might lead to a valine residue being translated instead to produce the mutated hemoglobin associated with sickle cell disease. But notice that if a mutation happens during translation, the cell will only ... | An introduction to genetic mutations Biomolecules MCAT Khan Academy.mp3 |
And since cells are making tons and tons of hemoglobin, just one mutated protein might not have that big of an effect on the cell. So we can say that mistakes during translation probably don't cause mutations like the one associated with sickle cell disease. So next, we'll look at mistakes during transcription. Again, ... | An introduction to genetic mutations Biomolecules MCAT Khan Academy.mp3 |
Again, we have our CTC piece of DNA, which would normally make GHG on RNA. But maybe a mistake occurs which leads to the transcription of a GUG instead, which would then code for the valine associated with mutated hemoglobin. Now, if this mistake occurred, the cell would only make a few mutated hemoglobins for each mis... | An introduction to genetic mutations Biomolecules MCAT Khan Academy.mp3 |
So we can say that mistakes during transcription probably don't cause mutations like the one associated with sickle cell disease. Finally, we'll look at mistakes in the DNA strand. If our CTC and DNA is mistakenly turned into a CAC, then our corresponding RNA from transcription will be changed. And ultimately, a valine... | An introduction to genetic mutations Biomolecules MCAT Khan Academy.mp3 |
And ultimately, a valine would be produced instead of a glutamic acid. Now, since a cell's DNA stores all of its genetic information, that mistake would lead to all future hemoglobins produced from that gene being mutated. So overall, we can say that mutations will usually result from mistakes in a cell's DNA and not f... | An introduction to genetic mutations Biomolecules MCAT Khan Academy.mp3 |
So where do these types of mutations come from? Well, there are two ways a person can get a genetic mutation. The first is that they inherit it from their parents. Remember that DNA is passed down from parents to offspring. So if we have a mutated father here, then there's a good chance that at least one of his kids wi... | An introduction to genetic mutations Biomolecules MCAT Khan Academy.mp3 |
Remember that DNA is passed down from parents to offspring. So if we have a mutated father here, then there's a good chance that at least one of his kids will inherit that mutated gene the same way that the child might inherit any amount of that parent's DNA. The other possibility is that the mutation will come on spon... | An introduction to genetic mutations Biomolecules MCAT Khan Academy.mp3 |
And spontaneous mutations can come from many different sources, with just a few examples being from DNA replication errors, environmental factors like certain poisons. Or it's also possible that genetic mutations can come on entirely randomly. So what did we learn? Well, first we learned that mutations originate at the... | An introduction to genetic mutations Biomolecules MCAT Khan Academy.mp3 |
It was named for Hades, or the ancient Greek underworld. Hades is also the name of the god that ran the Greek underworld, Zeus's oldest brother. And it was an appropriate name, although the idea of the ancient Greek notion of the underworld isn't exactly the more modern notion of hell. But it was a hellish environment.... | Beginnings of life Life on earth and in the universe Cosmology & Astronomy Khan Academy.mp3 |
But it was a hellish environment. You had all this lava flowing around. You had things impacting the Earth from space. And as far as we can tell right now, it was completely inhospitable to life. And to make matters worse, even though the Earth started to cool down a little bit, maybe the crust became a little bit more... | Beginnings of life Life on earth and in the universe Cosmology & Astronomy Khan Academy.mp3 |
And as far as we can tell right now, it was completely inhospitable to life. And to make matters worse, even though the Earth started to cool down a little bit, maybe the crust became a little bit more solid. Maybe the collisions started to happen less and less as we started to go a few hundred million years fast forwa... | Beginnings of life Life on earth and in the universe Cosmology & Astronomy Khan Academy.mp3 |
There was something called the late heavy bombardment. And right now the consensus is that whatever we are descended from would have had to come about after the late heavy bombardment. Because this was a time where so many things from outer space were hitting Earth that it was so violent that it might have killed off a... | Beginnings of life Life on earth and in the universe Cosmology & Astronomy Khan Academy.mp3 |
And I won't go into the physics of the late heavy bombardment, but we believe that it happened because Uranus and Neptune, so this is the sun right here. That is the sun. This is the asteroid belt that's outside the orbits of the inner rocky planets. That Uranus and Neptune, their orbits moved outward. And I'm not goin... | Beginnings of life Life on earth and in the universe Cosmology & Astronomy Khan Academy.mp3 |
That Uranus and Neptune, their orbits moved outward. And I'm not going to go into the physics, but what that caused is gravitationally it caused a lot of the asteroids in the asteroid belt to move inward and start impacting the inner planets. And of course, Earth was one of the inner planets. And I should make the sun ... | Beginnings of life Life on earth and in the universe Cosmology & Astronomy Khan Academy.mp3 |
And I should make the sun like orange or something, not blue. I don't want you to think that's Earth. And it also impacted the moon. And it's more obvious on the moon because the moon does not have an atmosphere to kind of smooth over the impact. So the consensus is that only after the late heavy bombardment was Earth ... | Beginnings of life Life on earth and in the universe Cosmology & Astronomy Khan Academy.mp3 |
And it's more obvious on the moon because the moon does not have an atmosphere to kind of smooth over the impact. So the consensus is that only after the late heavy bombardment was Earth kind of ready for life. And we believe that the first life formed 3.8 to 4 billion years ago. Remember, G for giga, 4 billion years a... | Beginnings of life Life on earth and in the universe Cosmology & Astronomy Khan Academy.mp3 |
Remember, G for giga, 4 billion years ago. And when we talk about life at this period, we're not talking about squirrels or panda bears. We're talking about extremely simple life forms. We're talking about prokaryotes. And let me give you a little primer on that right now, although we go into much more detail in the bi... | Beginnings of life Life on earth and in the universe Cosmology & Astronomy Khan Academy.mp3 |
We're talking about prokaryotes. And let me give you a little primer on that right now, although we go into much more detail in the biology playlist, we're talking about prokaryotes. And I'll compare them to eukaryotes. Prokaryotes are, for the most part, unicellular organisms that have no nucleuses. They also don't ha... | Beginnings of life Life on earth and in the universe Cosmology & Astronomy Khan Academy.mp3 |
Prokaryotes are, for the most part, unicellular organisms that have no nucleuses. They also don't have any other membrane-bound, what we'd call organelles, or these little parts of the cells that perform specific functions like mitochondria. So their DNA is just kind of floating around. So let me draw this character's ... | Beginnings of life Life on earth and in the universe Cosmology & Astronomy Khan Academy.mp3 |
So let me draw this character's DNA. So it's just floating around, just like that. And prokaryote literally means before kernel or before a nucleus. Eukaryotes do have a nucleus where all of their DNA is. So this is the nuclear membrane, and then all of its DNA is floating inside of the nucleus. And then it also has ot... | Beginnings of life Life on earth and in the universe Cosmology & Astronomy Khan Academy.mp3 |
Eukaryotes do have a nucleus where all of their DNA is. So this is the nuclear membrane, and then all of its DNA is floating inside of the nucleus. And then it also has other membrane-bound organelles. Mitochondria is kind of the most famous of them. So it also has things like mitochondria. We'll learn more about that ... | Beginnings of life Life on earth and in the universe Cosmology & Astronomy Khan Academy.mp3 |
Mitochondria is kind of the most famous of them. So it also has things like mitochondria. We'll learn more about that in future videos. Mitochondria, we believe, is essentially one prokaryote crawling inside of another prokaryote and kind of starting to become a symbiotic organism with each other. But I won't go into t... | Beginnings of life Life on earth and in the universe Cosmology & Astronomy Khan Academy.mp3 |
Mitochondria, we believe, is essentially one prokaryote crawling inside of another prokaryote and kind of starting to become a symbiotic organism with each other. But I won't go into that right now. But when we talk about life at this period, we're talking about prokaryotes. And we still have prokaryotes on the planet.... | Beginnings of life Life on earth and in the universe Cosmology & Astronomy Khan Academy.mp3 |
And we still have prokaryotes on the planet. Bacteria and archaea are examples of prokaryotes. And just to give you a little bit of a tidbit right here, this kind of shows our current understanding of where we think things branched off from. So at this point of the tree is some common ancestor to prokaryotes and eukary... | Beginnings of life Life on earth and in the universe Cosmology & Astronomy Khan Academy.mp3 |
So at this point of the tree is some common ancestor to prokaryotes and eukaryotes. So these are the prokaryotes right over here, the bacteria and the archaea. And here is the eukaryotes. And this first living thing, or this first set of living things, we think might have just been some type of self-replicating molecul... | Beginnings of life Life on earth and in the universe Cosmology & Astronomy Khan Academy.mp3 |
And this first living thing, or this first set of living things, we think might have just been some type of self-replicating molecules. And slowly some membrane might have come around and became a little bit more organized. DNA, RNA, maybe RNA was that original self-replicating molecule, became the method of kind of tr... | Beginnings of life Life on earth and in the universe Cosmology & Astronomy Khan Academy.mp3 |
So it's really still an open question of exactly what that first life is, or even how do you define that first life. But based on studying the genetic makeup of current organisms, this is how we think the tree of life came about. So we have one common ancestor, then they broke apart, and then the archaea and eukaryotes... | Beginnings of life Life on earth and in the universe Cosmology & Astronomy Khan Academy.mp3 |
And we'll talk more about that in the future. And this right here, just so you can visualize it, this is an example of bacteria. This is E. coli or Escherichia coli. It's just an example of bacteria. It comes in a bunch of shapes and forms. But it's a prokaryotic life form. And the earliest life forms we also think wer... | Beginnings of life Life on earth and in the universe Cosmology & Astronomy Khan Academy.mp3 |
It's just an example of bacteria. It comes in a bunch of shapes and forms. But it's a prokaryotic life form. And the earliest life forms we also think were anaerobes. These are things that did not need, one, that they did not need oxygen, and they, for the most part, found oxygen poisonous. And the earliest life forms ... | Beginnings of life Life on earth and in the universe Cosmology & Astronomy Khan Academy.mp3 |
And the earliest life forms we also think were anaerobes. These are things that did not need, one, that they did not need oxygen, and they, for the most part, found oxygen poisonous. And the earliest life forms also probably did not perform photosynthesis. They might have gotten their energy from other sources, chemica... | Beginnings of life Life on earth and in the universe Cosmology & Astronomy Khan Academy.mp3 |
They might have gotten their energy from other sources, chemically, from this kind of extremely volatile environment that they were in at that time. So if we fast forward a little bit, and this is actually a major event in the history of Earth. And these are huge timescales we're talking about. I mean, remember, I'm ki... | Beginnings of life Life on earth and in the universe Cosmology & Astronomy Khan Academy.mp3 |
I mean, remember, I'm kind of just nonchalantly saying, oh, 4.6 billion years ago to 3.8 billion years ago, that's just 800 million years. Remember, and I'll talk about this, grass has only existed for 50 million years. This is 800 million years. Humans and chimpanzees only diverged 5 million years ago. This is 800 mil... | Beginnings of life Life on earth and in the universe Cosmology & Astronomy Khan Academy.mp3 |
Humans and chimpanzees only diverged 5 million years ago. This is 800 million years we're talking about. From ancient Greece to now, we're only talking about 2,500 years. You multiply that times 1,000. You multiply that times 1,000, you get 2.5 million years. And this is 800 million years we're talking about. So these ... | Beginnings of life Life on earth and in the universe Cosmology & Astronomy Khan Academy.mp3 |
You multiply that times 1,000. You multiply that times 1,000, you get 2.5 million years. And this is 800 million years we're talking about. So these are extremely huge periods of time. And that's why we call them eons. Eons are 500 million to a billion years. Now, the dividing line between the Hadean Eon and the Archea... | Beginnings of life Life on earth and in the universe Cosmology & Astronomy Khan Academy.mp3 |
So these are extremely huge periods of time. And that's why we call them eons. Eons are 500 million to a billion years. Now, the dividing line between the Hadean Eon and the Archean Eon, and it's kind of a fuzzy dividing line, but most people place it about 3.8 billion years ago, is kind of the earliest rocks that we c... | Beginnings of life Life on earth and in the universe Cosmology & Astronomy Khan Academy.mp3 |
Now, the dividing line between the Hadean Eon and the Archean Eon, and it's kind of a fuzzy dividing line, but most people place it about 3.8 billion years ago, is kind of the earliest rocks that we can observe. And so we have rocks that are roughly 3.8 billion years ago, so we kind of put that as the beginning of the ... | Beginnings of life Life on earth and in the universe Cosmology & Astronomy Khan Academy.mp3 |
One, rocks have survived from the beginning of the Archean Eon, and also that's roughly when we think that the first life existed. And so we're now in the Archean Eon. And you might say, oh, maybe Earth is a more pleasant place now. But it would not be. It still has no to little oxygen in the environment. If you were t... | Beginnings of life Life on earth and in the universe Cosmology & Astronomy Khan Academy.mp3 |
But it would not be. It still has no to little oxygen in the environment. If you were to go to Earth at that time, it might have looked something like this. It would have been a reddish sky. You would have had nitrogen and methane and carbon dioxide in the atmosphere. There would have been nothing for you to breathe. T... | Beginnings of life Life on earth and in the universe Cosmology & Astronomy Khan Academy.mp3 |
It would have been a reddish sky. You would have had nitrogen and methane and carbon dioxide in the atmosphere. There would have been nothing for you to breathe. There still would have been a lot of volcanic activity. This right here, these are pictures of stromatolites. And these are formed from bacteria that are brin... | Beginnings of life Life on earth and in the universe Cosmology & Astronomy Khan Academy.mp3 |
There still would have been a lot of volcanic activity. This right here, these are pictures of stromatolites. And these are formed from bacteria that are bringing in sediment particles, and over time, these things get built up. But the most significant event in the Archean period, at least in my humble opinion, was wha... | Beginnings of life Life on earth and in the universe Cosmology & Astronomy Khan Academy.mp3 |
But the most significant event in the Archean period, at least in my humble opinion, was what we believe started to happen about 3.5 billion years ago. And this is prokaryotes, or especially bacteria, evolving to actually utilize energy from the sun to actually do photosynthesis. And the real fascinating byproduct of t... | Beginnings of life Life on earth and in the universe Cosmology & Astronomy Khan Academy.mp3 |
So it starts to produce oxygen. And at first, this oxygen, even though it was being produced by the cyanobacteria, by this blue-green bacteria, it really didn't accumulate in the atmosphere, because you had all of this iron that was dissolved in the oceans. And let me be clear, all of the life that we're going to be ta... | Beginnings of life Life on earth and in the universe Cosmology & Astronomy Khan Academy.mp3 |
We had no ozone layer now. The land was being irradiated. The land was just a completely inhospitable environment for life. So all of this was occurring in the ocean. And so the first oxygen that actually got produced, it actually, instead of just being released into the atmosphere, it ended up bonding with the iron th... | Beginnings of life Life on earth and in the universe Cosmology & Astronomy Khan Academy.mp3 |
So all of this was occurring in the ocean. And so the first oxygen that actually got produced, it actually, instead of just being released into the atmosphere, it ended up bonding with the iron that was dissolved in the ocean at that time. So it actually didn't have a chance to accumulate in the atmosphere. And when we... | Beginnings of life Life on earth and in the universe Cosmology & Astronomy Khan Academy.mp3 |
So in this table here, we have two different communities, community one and community two, and each of them contained three different species, and we see the populations of those three different species, and we also see that the total number of individuals in each community is the same. They both have a total of 1,000 ... | Simpson's index of diversity Ecology AP Biology Khan Academy.mp3 |
Community one or community two? All right, now let's think about this together. So as we already talked about, they have the same number of individuals, and you might be thinking that the number of species could be related to the diversity, and you'd be right. The number of species does contribute to the diversity, but... | Simpson's index of diversity Ecology AP Biology Khan Academy.mp3 |
The number of species does contribute to the diversity, but we're dealing with a situation where both communities have the same number of species. They each have three species. But when we look at the data, it's clear that community two is mostly species A, and you have very small groups of species B and species C, whi... | Simpson's index of diversity Ecology AP Biology Khan Academy.mp3 |
So just intuitively, it feels like community one is maybe more diverse. But this was just on my intuition or our intuition, and the numbers are pretty clear here. It's evenly distributed amongst the species here, and here it's very heavily weighted on species A. But it might not always be this clear, so it'd be useful ... | Simpson's index of diversity Ecology AP Biology Khan Academy.mp3 |
But it might not always be this clear, so it'd be useful to have some type of quantitative way to measure the diversity of a population. And lucky for us, there is a quantitative way to do that called Simpson's, I'll write it down, Simpson's diversity index. And the way you calculate it, it's equal to one minus the sum... | Simpson's index of diversity Ecology AP Biology Khan Academy.mp3 |
So for each of the species, you do this calculation, square it, and then you add it up for each of those species. So let's figure out Simpson's diversity index for both community one and community two. And I encourage you, you could pause the video and try to work on it on your own before I work through it with you. So... | Simpson's index of diversity Ecology AP Biology Khan Academy.mp3 |
So let's start with community one. So I'll say diversity index for community one, I'll just put that in parentheses, is going to be equal to one minus, so we have 325 over 1,000 squared. Remember, we're gonna sum on each of these species, plus 305, 305 over 1,000 squared, plus 370 over 1,000 squared. And I need to clos... | Simpson's index of diversity Ecology AP Biology Khan Academy.mp3 |
And I need to close my parentheses. And I can simplify this a little bit. This is going to be equal to one minus, so all of these 1,000 squareds, 1,000 squared is a million, so it's gonna be everything over one million, one million, and then we're going to have 325 squared plus 305 squared plus 370 squared. And that is... | Simpson's index of diversity Ecology AP Biology Khan Academy.mp3 |
And that is going to give us 325 squared plus 305 squared plus 370 squared is equal to that, that's the numerator here, now I'm gonna divide that by a million, divided by one, one, two, three, one, two, three, that is a million, it equals this, and then I'm gonna subtract that from one. So I'm just gonna put a negative... | Simpson's index of diversity Ecology AP Biology Khan Academy.mp3 |
Let's now explore the first law of thermodynamics. And before we're even talking about the first law of thermodynamics, some of you might be saying, well, what are thermodynamics? And you could tell from the roots of this word, you have thermo, related to thermal, it's dealing with temperature, and the dynamics, the pr... | First Law of Thermodynamics introduction Biology Khan Academy.mp3 |
How do they move? How does temperature behave? And that's pretty much what thermodynamics is. It's about, it's the study of heat and temperature and how it relates to energy and work and how different forms of energy can be transferred from one form to another. And that's actually at the heart of the first law of therm... | First Law of Thermodynamics introduction Biology Khan Academy.mp3 |
It's about, it's the study of heat and temperature and how it relates to energy and work and how different forms of energy can be transferred from one form to another. And that's actually at the heart of the first law of thermodynamics, which we touched on on the introduction to energy video. And the first law of therm... | First Law of Thermodynamics introduction Biology Khan Academy.mp3 |
Cannot be created, created or destroyed, or destroyed. It can only be converted from one form to another. It can, it can only, only be converted, only be converted, I'm having trouble writing today, converted from one form, from one form to another. Or you could transfer it, but you're not going to, you're not going to... | First Law of Thermodynamics introduction Biology Khan Academy.mp3 |
Or you could transfer it, but you're not going to, you're not going to create or destroy it. And the whole thing that I, the rest of this video, I just wanna really have you internalize that. And I wanna look at a bunch of examples and think about, well, what is the energy that we're observing or that we're seeing in a... | First Law of Thermodynamics introduction Biology Khan Academy.mp3 |
And then thinking about where is that energy coming from? That to appreciate that it's not just coming out of nowhere and that it's not just disappearing, it's not getting destroyed either. And so let's start with this example of a light bulb. And I encourage you to pause this video, think about the forms of energy tha... | First Law of Thermodynamics introduction Biology Khan Academy.mp3 |
And I encourage you to pause this video, think about the forms of energy that we can see here, and then think about where is that energy coming from and where is it going? Well, the most obvious form of energy that you see here, and this is the whole point of a light bulb, is you see the radiant energy. You see the ele... | First Law of Thermodynamics introduction Biology Khan Academy.mp3 |
And that light, so this is radiant energy, radiant energy, and that radiant energy, that radiant energy is due to the heat in the filament right over here, as the electrons go through it, it generates heat. So you have thermal energy. So you have thermal energy as well. Thermal, thermal energy. But where does this radi... | First Law of Thermodynamics introduction Biology Khan Academy.mp3 |
Thermal, thermal energy. But where does this radiant and thermal energy come from? Once again, the first law of thermodynamics tells us it's not just being created out of thin air, it must be converted or being transferred from someplace. Well, I just gave you a hint. This thermal energy is due to the electrons moving ... | First Law of Thermodynamics introduction Biology Khan Academy.mp3 |
Well, I just gave you a hint. This thermal energy is due to the electrons moving through the filament. They're moving through the filament, which has some resistance, and that generates heat. So the electrons are moving through this, and as they move through that resistor, they generate heat. So you actually have the k... | First Law of Thermodynamics introduction Biology Khan Academy.mp3 |
So the electrons are moving through this, and as they move through that resistor, they generate heat. So you actually have the kinetic energy of the electrons. I'll just write KE for short, kinetic energy of the actual electrons. Well, where is that kinetic energy coming from? Well, that's coming from the potential ene... | First Law of Thermodynamics introduction Biology Khan Academy.mp3 |
Well, where is that kinetic energy coming from? Well, that's coming from the potential energy. Maybe this thing is plugged into a socket of some kind. So let me draw an electric socket right over here. And the electric socket, I'll draw the electric socket, if this is the electric socket in your home, there is a electr... | First Law of Thermodynamics introduction Biology Khan Academy.mp3 |
So let me draw an electric socket right over here. And the electric socket, I'll draw the electric socket, if this is the electric socket in your home, there is a electrostatic potential between these two terminals. And so when you make a connection, the electrons are able to move. And we'll get into the details of AC ... | First Law of Thermodynamics introduction Biology Khan Academy.mp3 |
And we'll get into the details of AC and DC current in the future, but there's an electrostatic potential from this point to this point, if we assume that's the direction that the electrons are going in. And so it's that potential energy being converted to this kinetic energy of the electrons, which is really in the fo... | First Law of Thermodynamics introduction Biology Khan Academy.mp3 |
Now what happens after, let's say you unplug the light, the light goes dark, what happened to all of that energy? Is it still there? Well, yeah, that thermal energy is going to continue to dissipate through the system. And this right over here would be an open system. It's going to, the air inside the light bulb, you c... | First Law of Thermodynamics introduction Biology Khan Academy.mp3 |
And this right over here would be an open system. It's going to, the air inside the light bulb, you can't fully see the light bulb right here, but it looks something like this. That's going to heat up, but then it's going to heat up the glass surrounding the light bulb, and that's going to heat up the surrounding air. ... | First Law of Thermodynamics introduction Biology Khan Academy.mp3 |
So the thermal energy is going to be transferred, and that radiant energy is going to move outward, and it could be used, it could be converted into other forms of energy, most likely thermal energy. It is also probably going to heat up other things. Well, what about a pool table? When I hit a, if I hit a pool, a billi... | First Law of Thermodynamics introduction Biology Khan Academy.mp3 |
When I hit a, if I hit a pool, a billiard ball or a pool ball right over here, well, where's that energy going? Well, some of that energy might be going to go hit the next ball, which might go to hit the next ball, but as we all know, if we've ever played pool, at some point, they're going to stop. So what happened to ... | First Law of Thermodynamics introduction Biology Khan Academy.mp3 |
Well, while they were rolling, while they were rolling, there was some air resistance. There was some air resistance, so they're bumping against the air molecules, and it's really friction due to air, and that energy is essentially going to be converted to heat. And one trend that you're going to see very frequently is... | First Law of Thermodynamics introduction Biology Khan Academy.mp3 |
And so you're going to have, as the billiard balls move, there's the air, and so that's going to be converted, some of that kinetic energy is going to be turned into heat energy. You're also going to have friction with the actual felt on the table, and that friction, you're going to have molecules rubbing up against ea... | First Law of Thermodynamics introduction Biology Khan Academy.mp3 |
Now what about this weightlifter here? He's using the chemical energy in the ATP in his muscles that converts into kinetic energy that moves his muscles, that moves this weight, but once he's in this position, what happened to all of that energy? Well, a lot of that energy is now being stored in potential, it's the pot... | First Law of Thermodynamics introduction Biology Khan Academy.mp3 |
He's got this big weight, he's got that big weight above his head, and if he were to just let go, that thing would fall. I wouldn't recommend he do that, but that thing would fall quite fast, and so now it's all, or a lot of it, has been stored up in potential energy, but he would have also generated heat. His muscles ... | First Law of Thermodynamics introduction Biology Khan Academy.mp3 |
It is being converted from one form or another, being transferred from one part of the system to another. Now we can look at these examples over here. Same thing with a runner. What happens after, you can buy the fact that okay, his chemical energy is allowing his muscles to move, and that's turning into his whole kine... | First Law of Thermodynamics introduction Biology Khan Academy.mp3 |
What happens after, you can buy the fact that okay, his chemical energy is allowing his muscles to move, and that's turning into his whole kinetic energy for his entire body. His body is moving, but at some point he stops. Where did all that energy go? Well, some of it will be heat in his body that's being dissipated i... | First Law of Thermodynamics introduction Biology Khan Academy.mp3 |
Well, some of it will be heat in his body that's being dissipated into the broader system, into the air, and also when he was running, there was this contact with the ground. That's gonna make the molecules in the ground vibrate a little bit. Some of it will be transferred as sound, so the air particles moving through ... | First Law of Thermodynamics introduction Biology Khan Academy.mp3 |
The diver up here, you have mostly potential energy. Then it converts to kinetic energy as he's get almost in the water, but what happens once he falls into the water? Well, then that energy is going to be transferred as you're gonna have these waves of water move away, and it will also increase friction. So, well, act... | First Law of Thermodynamics introduction Biology Khan Academy.mp3 |
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