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Population diversity and resilience Natural selection AP Biology Khan Academy (2).mp3 | So let's imagine that each of these little circles here represent a member of a population of bugs. And we have two different populations of bugs. You could view this as population one on the left side of this orange line and population two on the right side of this orange line. And these bugs, we're gonna think about ... |
Population diversity and resilience Natural selection AP Biology Khan Academy (2).mp3 | And these bugs, we're gonna think about just one trait, their color, because it's easy to visualize. And let's say that their color generally helps them camouflage from predators. So this kind of cloudy white and black and green layer, that's maybe the environment that they're in where you might find them. Maybe it's t... |
Population diversity and resilience Natural selection AP Biology Khan Academy (2).mp3 | Maybe it's the surface of a moss-covered tree or something like that. And these are two separate populations of maybe a related species or maybe the same species, but they're two different populations that are not intermixing. Now, the first question is, which of these populations has more genetic diversity? Well, on t... |
Population diversity and resilience Natural selection AP Biology Khan Academy (2).mp3 | Well, on the left here, we see that they're all the same color. It looks like a pretty useful color. It seems to hide them pretty well, camouflage them pretty well. On the right here, it's clear that there's more different types of color. Some of them are roughly the same color as what we see on the left-hand side, but... |
Population diversity and resilience Natural selection AP Biology Khan Academy (2).mp3 | On the right here, it's clear that there's more different types of color. Some of them are roughly the same color as what we see on the left-hand side, but some of them are a good bit darker and some of them are a good bit lighter. So the one on the right, the population on the right, has more diversity. Now, one could... |
Population diversity and resilience Natural selection AP Biology Khan Academy (2).mp3 | Now, one could argue that some of these very bright circles or some of these darker circles might be more susceptible to predators, and that actually might be the case. But what we're gonna think about in this video is not how many members of the population may be more or less susceptible to predators. What we're gonna... |
Population diversity and resilience Natural selection AP Biology Khan Academy (2).mp3 | Does it make the population as a whole more resilient? I'm not talking about any individual member of the population. And to imagine that, let's imagine that there's some type of environmental change, maybe there's pollution in the area, that makes the surfaces that these little bugs have to live on a good bit darker. ... |
Population diversity and resilience Natural selection AP Biology Khan Academy (2).mp3 | So maybe the surfaces look like this. So now what's likely to happen? Well, in this reality, all of the bugs on our left-hand side are now more visible to predators. And so you can imagine the predators might be able to pick off a lot more of them, or in an extreme case, maybe able to finish them off all together, whil... |
Population diversity and resilience Natural selection AP Biology Khan Academy (2).mp3 | And so you can imagine the predators might be able to pick off a lot more of them, or in an extreme case, maybe able to finish them off all together, while on the right, some of the members of the population are easier to pick off, like that one and that one and that one and that one, while some other members of the po... |
Population diversity and resilience Natural selection AP Biology Khan Academy (2).mp3 | And you could imagine it the other way around. Let's say instead of the environment getting somehow darker, imagine if the environment got somehow lighter, something like that. Well, you see a similar phenomenon. All the ones on the left are now very similarly visible, and maybe the predators could pick them off, while... |
Population diversity and resilience Natural selection AP Biology Khan Academy (2).mp3 | All the ones on the left are now very similarly visible, and maybe the predators could pick them off, while on the right, some of them have become a lot more visible, in this case, the darker ones are now super visible, the predators might be able to pick them off and even some of the medium colored, but there's a good... |
Soil Texture Triangle Earth systems and resources AP environmental science Khan Academy.mp3 | The soil near a beach looks and feels very different than the soil in a forest. And part of the reason for that difference is something called soil texture. Soil texture. So when soil is formed, different types of rock break down because of the wind and the rain and the weather, and they become differently sized partic... |
Soil Texture Triangle Earth systems and resources AP environmental science Khan Academy.mp3 | So when soil is formed, different types of rock break down because of the wind and the rain and the weather, and they become differently sized particles. And the combination of these differently sized particles creates soil texture. So these differently sized particles can be broken down into three groups. We have sand... |
Soil Texture Triangle Earth systems and resources AP environmental science Khan Academy.mp3 | We have sand, we have silt, and we have clay. Sand is made up of the larger and heavier particles of soil. Sand is around 2 millimeters, 2 millimeters to 0.05 millimeters, which is a twentieth of a millimeter in diameter. And it feels very gritty to touch. Clay on the other hand is the smallest particles of soil. It's ... |
Soil Texture Triangle Earth systems and resources AP environmental science Khan Academy.mp3 | And it feels very gritty to touch. Clay on the other hand is the smallest particles of soil. It's around 0.002 millimeters and smaller. That's a five hundredth of a millimeter. So really tiny. If you rubbed clay between your fingers, it would feel smooth and you wouldn't be able to feel the individual particles of soil... |
Soil Texture Triangle Earth systems and resources AP environmental science Khan Academy.mp3 | That's a five hundredth of a millimeter. So really tiny. If you rubbed clay between your fingers, it would feel smooth and you wouldn't be able to feel the individual particles of soil. And unlike sand, you can't even see clay's particles with the naked eye. Most people are familiar with sandy soils and clayey soils, b... |
Soil Texture Triangle Earth systems and resources AP environmental science Khan Academy.mp3 | And unlike sand, you can't even see clay's particles with the naked eye. Most people are familiar with sandy soils and clayey soils, but silt is right in between. It's made up of particles between the sizes of clay and sand. So it's between 0.05 millimeters and 0.002 millimeters. So when you think of silt, imagine baki... |
Soil Texture Triangle Earth systems and resources AP environmental science Khan Academy.mp3 | So it's between 0.05 millimeters and 0.002 millimeters. So when you think of silt, imagine baking flour. It's powdery. Powdery. And it can be carried easily by wind and water. But soil is more complicated than just these three soil types. If you grabbed a handful of soil from outside your home, it would probably be a c... |
Soil Texture Triangle Earth systems and resources AP environmental science Khan Academy.mp3 | Powdery. And it can be carried easily by wind and water. But soil is more complicated than just these three soil types. If you grabbed a handful of soil from outside your home, it would probably be a combination of all three soil types, along with some organic material. A soil's unique texture, that is, its combination... |
Soil Texture Triangle Earth systems and resources AP environmental science Khan Academy.mp3 | If you grabbed a handful of soil from outside your home, it would probably be a combination of all three soil types, along with some organic material. A soil's unique texture, that is, its combination of silt, sand, and clay, affects how plants will grow. And so gardeners often want to know about their soil texture, so... |
Soil Texture Triangle Earth systems and resources AP environmental science Khan Academy.mp3 | This is where a helpful diagram called the soil texture triangle comes in. The soil texture triangle. The triangle allows us to place any soil sample into one of 12 different soil texture categories. The 12 different categories are broken up based on the percentage of silt, clay, and sand in the soil. To see how this w... |
Soil Texture Triangle Earth systems and resources AP environmental science Khan Academy.mp3 | The 12 different categories are broken up based on the percentage of silt, clay, and sand in the soil. To see how this works, let's do an example. Let's say a gardener determined that her soil was 30% sand, 40% silt, and 30% clay. So how can we figure out what kind of soil we have? First, we need to pick a side of the ... |
Soil Texture Triangle Earth systems and resources AP environmental science Khan Academy.mp3 | So how can we figure out what kind of soil we have? First, we need to pick a side of the triangle to start with. I'll start with sand. We know we have 30% sand, so we go along the side of the triangle until we find the 30% mark, right here. We want to draw a line from this point to the side of the triangle that this ar... |
Soil Texture Triangle Earth systems and resources AP environmental science Khan Academy.mp3 | We know we have 30% sand, so we go along the side of the triangle until we find the 30% mark, right here. We want to draw a line from this point to the side of the triangle that this arrow is pointing to. The arrow is pointing towards the clay side, so we draw the line from the 30% sand mark through the triangle to the... |
Soil Texture Triangle Earth systems and resources AP environmental science Khan Academy.mp3 | And by drawing this line, we already know that our soil sample will fall into a category along this line. So it could be silt loam, loam, clay loam, or clay. But to figure out exactly where it is, let's draw another line. Let's do silt. The soil has 40% silt. We'll draw our line through the triangle towards the sand si... |
Soil Texture Triangle Earth systems and resources AP environmental science Khan Academy.mp3 | Let's do silt. The soil has 40% silt. We'll draw our line through the triangle towards the sand side because of this arrow. So again, we do the same thing. We go along the percent silt line, we find the 40% mark, and we're going to draw a line from 40% to the other side of the triangle. And you can see, when we draw th... |
Soil Texture Triangle Earth systems and resources AP environmental science Khan Academy.mp3 | So again, we do the same thing. We go along the percent silt line, we find the 40% mark, and we're going to draw a line from 40% to the other side of the triangle. And you can see, when we draw that line, these two lines intersect at the clay loam point. But to double check, let's draw a line from the 30% clay mark to ... |
Soil Texture Triangle Earth systems and resources AP environmental science Khan Academy.mp3 | But to double check, let's draw a line from the 30% clay mark to the other side of the triangle, like this. As you can see, these three lines all intersected at the same point, right here in clay loam. So we know that we have clay loam. Notice that the percentage of clay, silts, and sand all add up to a total of 100%. ... |
Soil Texture Triangle Earth systems and resources AP environmental science Khan Academy.mp3 | Notice that the percentage of clay, silts, and sand all add up to a total of 100%. We could have picked any two of these lines, just two, to find our answer. We don't need to draw three lines every time. Let's do another example. Let's say our gardener has another plot with soil that contains 58% sand, 27% silts, and 1... |
Soil Texture Triangle Earth systems and resources AP environmental science Khan Academy.mp3 | Let's do another example. Let's say our gardener has another plot with soil that contains 58% sand, 27% silts, and 15% clay. So I'm going to go along the percent sand part and find 58%. So that's pretty close to 60. I'm going to draw a line from 58% to the other side of the triangle. Sometimes the example question does... |
Soil Texture Triangle Earth systems and resources AP environmental science Khan Academy.mp3 | So that's pretty close to 60. I'm going to draw a line from 58% to the other side of the triangle. Sometimes the example question doesn't give us round numbers to work with. So when that's the case, I like to use a ruler or a straight edge, just to make sure that my lines are in the correct spot. Next I'm going to use ... |
Soil Texture Triangle Earth systems and resources AP environmental science Khan Academy.mp3 | So when that's the case, I like to use a ruler or a straight edge, just to make sure that my lines are in the correct spot. Next I'm going to use the 15% clay. So I find the 15% clay mark, and we draw a line from 15% to the other side of the triangle, following the direction of the lines within the triangle. And we can... |
Soil Texture Triangle Earth systems and resources AP environmental science Khan Academy.mp3 | And we can see that our two lines intersect at this point. So we have sandy loam. The gardener has these two plots, clay loam and sandy loam. So when the gardener looks at her two plots, she might want to take into account the different kinds of soil. Certain kinds of plants do better in clay loam soil, while others wo... |
Acid Rain Atmospheric Pollution AP Environmental science Khan Academy (2).mp3 | Acid rain sounds like something straight out of a sci-fi film, like strange raindrops that fall on a city and corrode everything. The truth is not far off, but the good news is that we know a lot about what causes acid rain and how to address its impact on the environment, our bodies, and the built world. Interestingly... |
Acid Rain Atmospheric Pollution AP Environmental science Khan Academy (2).mp3 | If you think back to the pH scale, you'll remember that it goes from 0 to 14, acidic to basic, and that 7 right in the middle is neutral. Normal rain is around 5 or 5.5, so it's slightly acidic. But acid rain is even more acidic, and typically around a pH of 4. Now this might not sound like a big difference, but rememb... |
Acid Rain Atmospheric Pollution AP Environmental science Khan Academy (2).mp3 | Now this might not sound like a big difference, but remember that this is a logarithmic scale, so each increment, like from 4 to 5, is actually a tenfold difference. So if we're comparing normal rain at about 5.5 and acid rain at 4, that's a pretty big deal. So now the questions are, how does acid rain form, why does i... |
Acid Rain Atmospheric Pollution AP Environmental science Khan Academy (2).mp3 | So the short answer to how it forms is pollution. So let me try to bring that to life for you with my imaginary hand-drawn city. Now remember that most of the fuels we burn to make energy are from fossil fuels, so that animal and plant matter that has been in the ground for millions of years. And when we burn these fue... |
Acid Rain Atmospheric Pollution AP Environmental science Khan Academy (2).mp3 | And when we burn these fuels, they tend to have remaining traces of sulfur in them, especially coal. Both coal and oil burn at such high temperatures that they can cause nitrogen and oxygen in the air to form different compounds. So imagine we have here an oil refinery and a coal-burning plant and a lot of cars. A comm... |
Acid Rain Atmospheric Pollution AP Environmental science Khan Academy (2).mp3 | A common byproduct of coal-burning plants, ore smelters, and other industrial facilities is sulfur dioxide, SO2. At the same time, high temperatures from combustion engines and oil refineries provide enough energy to break apart nitrogen and oxygen molecules in the air. These molecules can then recombine to form differ... |
Acid Rain Atmospheric Pollution AP Environmental science Khan Academy (2).mp3 | Together, these are referred to as nitrogen oxides, which you can abbreviate by NOx. So the same can be said about sulfur dioxide, that falls into the category of sulfur oxide, SOx, or SOx. So a fun way to remember the precursors to acid rain are SOx and NOx. Now these precursors belonging to the SOx and NOx family are... |
Acid Rain Atmospheric Pollution AP Environmental science Khan Academy (2).mp3 | Now these precursors belonging to the SOx and NOx family are hanging out up in the air. When they interact with UV radiation from the sun and water molecules that are also in the air, they form different vapors. These acid vapors, sulfuric acid vapor, H2SO4, and nitric acid vapor, HNO3. And these acids are no joke. Sul... |
Acid Rain Atmospheric Pollution AP Environmental science Khan Academy (2).mp3 | And these acids are no joke. Sulfuric acid is highly corrosive. It can burn your skin. The vapors can irritate your respiratory tract. And nitric acid is known to be used in explosives and rocket launches. And these are the acids that make up the phenomenon of acid rain. Over time, these smokestacks have actually gotte... |
Acid Rain Atmospheric Pollution AP Environmental science Khan Academy (2).mp3 | The vapors can irritate your respiratory tract. And nitric acid is known to be used in explosives and rocket launches. And these are the acids that make up the phenomenon of acid rain. Over time, these smokestacks have actually gotten taller. One example, in the early 1970s, when the EPA wanted to reduce emissions from... |
Acid Rain Atmospheric Pollution AP Environmental science Khan Academy (2).mp3 | Over time, these smokestacks have actually gotten taller. One example, in the early 1970s, when the EPA wanted to reduce emissions from these coal burning facilities and oil refineries to control the air quality around those communities, what these facilities did was build larger smokestacks or taller smokestacks so th... |
Acid Rain Atmospheric Pollution AP Environmental science Khan Academy (2).mp3 | Up to a thousand kilometers or over 600 miles. And when these acid vapors cause acid rain, it's not always rain like we think of with water falling from the sky. Acid rain is just a general term and it really includes all forms of precipitation, like snow, fog, cloud vapor, and dry deposition like dust particles. And a... |
Acid Rain Atmospheric Pollution AP Environmental science Khan Academy (2).mp3 | And also it can have different combinations of these forms. And now the other big question is, why does it matter, right? How are we affected? And also, does that acid burn your skin? A very logical thing to want to know. So for cities, first of all, acid rain is bad news because it can damage buildings and statues, pa... |
Acid Rain Atmospheric Pollution AP Environmental science Khan Academy (2).mp3 | And also, does that acid burn your skin? A very logical thing to want to know. So for cities, first of all, acid rain is bad news because it can damage buildings and statues, particularly those that are made of limestone, marble, and some metals. Here in this photo is a gargoyle from the Munich Town Hall, which is almo... |
Acid Rain Atmospheric Pollution AP Environmental science Khan Academy (2).mp3 | Here in this photo is a gargoyle from the Munich Town Hall, which is almost unrecognizable because of all of the damage it's sustained from acid rain. There's also been a lot of studies over the years looking at the US Capitol and a lot of the surfaces there that are made of marble and how they can strengthen them to p... |
Acid Rain Atmospheric Pollution AP Environmental science Khan Academy (2).mp3 | Many fish can't survive at a lower pH. Acid rain also has impacts on other natural environments, especially because of how far it reaches. Acid rain can damage and weaken forests and trees by stripping nutrients from the soil and even damaging the waxy outer coat, leaving them much more vulnerable to losing more nutrie... |
Acid Rain Atmospheric Pollution AP Environmental science Khan Academy (2).mp3 | Now when it comes to humans, these acid vapors and the different precipitation that they create are very harmful to our respiratory system, and especially those that have asthma. And of course, I have to answer the question, does acid rain burn your skin? The answer is no. It's just not acidic enough. Remember acid rai... |
Acid Rain Atmospheric Pollution AP Environmental science Khan Academy (2).mp3 | It's just not acidic enough. Remember acid rain is around a pH of 4, and for something to burn your skin, it has to be much more acidic, usually around a pH of 1. There is some good news when it comes to acid rain. In 1990, the EPA created the Acid Rain Program to help power plants reduce emissions. In 2019, when they ... |
Acid Rain Atmospheric Pollution AP Environmental science Khan Academy (2).mp3 | In 1990, the EPA created the Acid Rain Program to help power plants reduce emissions. In 2019, when they looked at the levels compared to 1990, they saw pretty great reductions. A 94% reduction in sulfur dioxide, and an 86% reduction in nitric oxides. Now this is in the United States, but around the world, acid rain is... |
Reduction of Air Pollutants Atmospheric Pollution AP Environmental Science Khan Academy (2).mp3 | It's the middle of the day but there's a thick yellowish smog everywhere enveloping everything and even blocking out the Sun. It's so dark that streetlights are on during the daytime. It stings your eyes and it's hard, even painful, to breathe. What we're experiencing is the Donora death fog, one of the worst air pollu... |
Reduction of Air Pollutants Atmospheric Pollution AP Environmental Science Khan Academy (2).mp3 | What we're experiencing is the Donora death fog, one of the worst air pollution disasters in the United States. Donora was an industrial town full of steel plants and mills which released toxic emissions such as hydrogen fluoride and sulfur dioxide when processing steel and other metals. Normally these poisonous gases ... |
Reduction of Air Pollutants Atmospheric Pollution AP Environmental Science Khan Academy (2).mp3 | Consequently the toxic emissions were essentially trapped under the warm air. Over the course of several days from October 26th to October 31st these toxic emissions had accumulated so much that half of the 14,000 people living in Donora suffered from respiratory problems and 20 people died. Relief only came when the s... |
Reduction of Air Pollutants Atmospheric Pollution AP Environmental Science Khan Academy (2).mp3 | But following the deadly Donora smog the public began to realize just how dangerous and life-threatening air pollution could be and citizens demanded change. Donora became a turning point in US history and was the start of the clean air movement. The Air Pollution Control Act of 1955 was the first piece of US federal l... |
Reduction of Air Pollutants Atmospheric Pollution AP Environmental Science Khan Academy (2).mp3 | Then in 1963 the Clean Air Act was passed, the first federal legislation to control air pollution, and later expanded in 1970 which resulted in the creation of the US Environmental Protection Agency, the EPA, to develop and enforce regulations to protect the general public from exposure to major outdoor air pollutants.... |
Reduction of Air Pollutants Atmospheric Pollution AP Environmental Science Khan Academy (2).mp3 | These four main air pollutants that I highlighted are largely released as emissions from burning fossil fuels which comes from driving vehicles and operating coal-fired power plants and other industrial facilities. So as we've started to drive more efficient vehicles and obtain more energy from clean renewable sources ... |
Reduction of Air Pollutants Atmospheric Pollution AP Environmental Science Khan Academy (2).mp3 | How do we clean the air and limit emissions of harmful pollutants? Clean Air Act regulations implemented by the EPA have led to new technologies that help to limit emissions and remove pollutants from the air. In particular many of these technologies help to reduce air pollution from coal-burning power plants and vehic... |
Reduction of Air Pollutants Atmospheric Pollution AP Environmental Science Khan Academy (2).mp3 | Each of these pollution control technologies functions to remove harmful components out of emissions and release a less harmful substance. In the last decade or so you've also probably noticed more and more electric vehicles on the road. Improving the fuel economy of vehicles and even using battery powered electric veh... |
Reduction of Air Pollutants Atmospheric Pollution AP Environmental Science Khan Academy (2).mp3 | A good example is the growing demand for hybrid and purely electric vehicles. Here we have a simplified figure that explains the sources of energy for different types of vehicles and their respective emissions. On the left we have conventional vehicles which rely on fossil fuels such as gasoline or diesel and when driv... |
Reduction of Air Pollutants Atmospheric Pollution AP Environmental Science Khan Academy (2).mp3 | Hybrid and plug-in hybrid vehicles are similar to conventional vehicles and that they have an internal combustion engine but they also have an electric motor which uses energy stored in batteries. These batteries can be charged by regenerative braking or in the case of plug-in hybrids just by using a wall outlet or oth... |
Reduction of Air Pollutants Atmospheric Pollution AP Environmental Science Khan Academy (2).mp3 | Finally vehicles that rely solely on electricity known as battery electric vehicles or BEVs can use an alternative electricity source so that there's no emissions at the source of the electricity. What else can we do to ensure cleaner air? We can reduce our reliance on fossil fuels and instead invest in cleaner renewab... |
Reduction of Air Pollutants Atmospheric Pollution AP Environmental Science Khan Academy (2).mp3 | And we can make decisions in our day-to-day lives to reduce or prevent air pollution by using less energy and alternative fuels. For example walking, biking, or using mass transportation can reduce the need to burn fossil fuels and there are plenty of other ways to reduce our electrical needs in particular using more e... |
Stratospheric Ozone Depletion Global change AP Environmental Science Khan Academy (2).mp3 | And ozone, you can also view as O3 or three oxygens bonded this way. These dashed lines show that sometimes the double bond is on this side, sometimes it's on that side. You might recognize that as resonance in molecular structures or resonance in bonds. But it plays some very interesting roles. It can both protect us ... |
Stratospheric Ozone Depletion Global change AP Environmental Science Khan Academy (2).mp3 | But it plays some very interesting roles. It can both protect us and it can hurt us. And to understand this, let's look at this diagram of the atmosphere. So there's a lot of really interesting information in this diagram, some of it relevant to this video, some of it not, but I encourage you to look at it. There's jus... |
Stratospheric Ozone Depletion Global change AP Environmental Science Khan Academy (2).mp3 | So there's a lot of really interesting information in this diagram, some of it relevant to this video, some of it not, but I encourage you to look at it. There's just all sorts of cool things, how temperature changes as we increase in altitude. We see the labels of the major layers of the atmosphere. We can compare it ... |
Stratospheric Ozone Depletion Global change AP Environmental Science Khan Academy (2).mp3 | We can compare it to Mount Everest and where clouds are. But we see a few things. We have a troposphere, and then above that we have a stratosphere. Now, in the stratosphere, we see this thing known as an ozone layer, which is 10 to 20 miles above the surface of the Earth. And ozone in this part of the atmosphere prote... |
Stratospheric Ozone Depletion Global change AP Environmental Science Khan Academy (2).mp3 | Now, in the stratosphere, we see this thing known as an ozone layer, which is 10 to 20 miles above the surface of the Earth. And ozone in this part of the atmosphere protects us. How does it protect us? Well, the sun, which most of us consider our friend that lives 93 million miles away, we know that life wouldn't exis... |
Stratospheric Ozone Depletion Global change AP Environmental Science Khan Academy (2).mp3 | Well, the sun, which most of us consider our friend that lives 93 million miles away, we know that life wouldn't exist without the sun. Most of the energy we have on this planet is because of the sun. But UV frequencies from the sun, if they aren't blocked or if they aren't mitigated a little bit, they can cause a lot ... |
Stratospheric Ozone Depletion Global change AP Environmental Science Khan Academy (2).mp3 | They have a lot of energy. They can affect molecules. And in particular, they can affect our DNA. And if you start messing with DNA, start mutating DNA, that can lead to things like cancer. And so you could imagine we human beings, and actually most organisms, can only deal with a certain amount of UV light. Now, if we... |
Stratospheric Ozone Depletion Global change AP Environmental Science Khan Academy (2).mp3 | And if you start messing with DNA, start mutating DNA, that can lead to things like cancer. And so you could imagine we human beings, and actually most organisms, can only deal with a certain amount of UV light. Now, if we had no ozone layer, a lot of that UV light would come in unchecked. It's going to get absorbed a ... |
Stratospheric Ozone Depletion Global change AP Environmental Science Khan Academy (2).mp3 | It's going to get absorbed a little bit by the various layers of the atmosphere, but it turns out that ozone in particular is good at protecting us from UV light. So if we didn't have this ozone layer above us, you would see cancer rates go up. We would just get a lot more UV energy. Now, an interesting question is, ho... |
Stratospheric Ozone Depletion Global change AP Environmental Science Khan Academy (2).mp3 | Now, an interesting question is, how does this ozone layer form? We're not used to seeing oxygen in this form. Most of the oxygen that we see in our atmosphere is molecular oxygen in the form of two oxygens, which looks like that. Well, it turns out that UV light actually helps create the thing that protects us from UV... |
Stratospheric Ozone Depletion Global change AP Environmental Science Khan Academy (2).mp3 | Well, it turns out that UV light actually helps create the thing that protects us from UV light, because O2 in the presence of UV can be broken up and then reformed as ozone. So it's actually the fact that you have so much UV light up here that it reacts with oxygen that has raised to the stratosphere, and some of that... |
Stratospheric Ozone Depletion Global change AP Environmental Science Khan Academy (2).mp3 | It has a very short half-life. It is way less stable than O2. And so it has to keep getting replenished in the atmosphere. And we also know that certain chemicals that we human beings have produced, in particular what's often known as chlorofluorocarbons, and that's just a fancy way of saying molecules that are hydroca... |
Stratospheric Ozone Depletion Global change AP Environmental Science Khan Academy (2).mp3 | And we also know that certain chemicals that we human beings have produced, in particular what's often known as chlorofluorocarbons, and that's just a fancy way of saying molecules that are hydrocarbons, so a bunch of carbons and hydrogens, that also involve chlorine and fluorine. And these molecules were generated in ... |
Stratospheric Ozone Depletion Global change AP Environmental Science Khan Academy (2).mp3 | They'll come up from our little spray paint cans, and they'll interact with the ozone, and they will deplete it, which is not a good thing. Once again, it will make us all more susceptible to things like cancer. Now, everything we've talked about so far is ozone in the stratosphere, but it turns out that ozone can actu... |
Stratospheric Ozone Depletion Global change AP Environmental Science Khan Academy (2).mp3 | And when ozone is down there, it's actually a bad thing. And to understand why it might form down there, we need to understand the role, once again, that we're playing. Nitrous oxides are formed from automobile exhaust and coal-fired power plants. And when those, in the presence of UV light, and what's known as volatil... |
Stratospheric Ozone Depletion Global change AP Environmental Science Khan Academy (2).mp3 | And when those, in the presence of UV light, and what's known as volatile organic compounds, which is just a fancy way of saying organic compounds that evaporate very easily, and most of these are naturally produced, the VOCs, but when you have the UV light in conjunction with the exhaust from automobiles and nitrous o... |
Stratospheric Ozone Depletion Global change AP Environmental Science Khan Academy (2).mp3 | It can damage our respiratory systems. So you don't want ozone around. So it's good in the upper atmosphere, and it is bad in the lower atmosphere. So I will leave you there. You got your primer on ozone. And just recognize, the same thing that can help us in one place can hurt us in another place. And the same thing t... |
Stratospheric Ozone Depletion Global change AP Environmental Science Khan Academy.mp3 | These dashed lines show that sometimes the double bond is on this side, sometimes it's on that side. You might recognize that as resonance in molecular structures or resonance in bonds. But it plays some very interesting roles. It can both protect us and it can hurt us. And to understand this, let's look at this diagra... |
Stratospheric Ozone Depletion Global change AP Environmental Science Khan Academy.mp3 | It can both protect us and it can hurt us. And to understand this, let's look at this diagram of the atmosphere. So there's a lot of really interesting information in this diagram, some of it relevant to this video, some of it not, but I encourage you to look at it. There's just all sorts of cool things, how temperatur... |
Stratospheric Ozone Depletion Global change AP Environmental Science Khan Academy.mp3 | There's just all sorts of cool things, how temperature changes as we increase in altitude. We see the labels of the major layers of the atmosphere. We can compare it to Mount Everest and where clouds are. But we see a few things. We have a troposphere, and then above that we have a stratosphere. Now, in the stratospher... |
Stratospheric Ozone Depletion Global change AP Environmental Science Khan Academy.mp3 | But we see a few things. We have a troposphere, and then above that we have a stratosphere. Now, in the stratosphere, we see this thing known as an ozone layer, which is 10 to 20 miles above the surface of the Earth. And ozone in this part of the atmosphere protects us. How does it protect us? Well, the sun, which most... |
Stratospheric Ozone Depletion Global change AP Environmental Science Khan Academy.mp3 | And ozone in this part of the atmosphere protects us. How does it protect us? Well, the sun, which most of us consider our friend that lives 93 million miles away, we know that life wouldn't exist without the sun. Most of the energy we have on this planet is because of the sun. But UV frequencies from the sun, if they ... |
Stratospheric Ozone Depletion Global change AP Environmental Science Khan Academy.mp3 | Most of the energy we have on this planet is because of the sun. But UV frequencies from the sun, if they aren't blocked or if they aren't mitigated a little bit, they can cause a lot of damage. They have a lot of energy. They can affect molecules. And in particular, they can affect our DNA. And if you start messing wi... |
Stratospheric Ozone Depletion Global change AP Environmental Science Khan Academy.mp3 | They can affect molecules. And in particular, they can affect our DNA. And if you start messing with DNA, start mutating DNA, that can lead to things like cancer. And so you could imagine we human beings, and actually most organisms, can only deal with a certain amount of UV light. Now, if we had no ozone layer, a lot ... |
Stratospheric Ozone Depletion Global change AP Environmental Science Khan Academy.mp3 | And so you could imagine we human beings, and actually most organisms, can only deal with a certain amount of UV light. Now, if we had no ozone layer, a lot of that UV light would come in unchecked. It's going to get absorbed a little bit by the various layers of the atmosphere, but it turns out that ozone in particula... |
Stratospheric Ozone Depletion Global change AP Environmental Science Khan Academy.mp3 | So if we didn't have this ozone layer above us, you would see cancer rates go up. We would just get a lot more UV energy. Now, an interesting question is, how does this ozone layer form? We're not used to seeing oxygen in this form. Most of the oxygen that we see in our atmosphere is molecular oxygen in the form of two... |
Stratospheric Ozone Depletion Global change AP Environmental Science Khan Academy.mp3 | We're not used to seeing oxygen in this form. Most of the oxygen that we see in our atmosphere is molecular oxygen in the form of two oxygens, which looks like that. Well, it turns out that UV light actually helps create the thing that protects us from UV light, because O2 in the presence of UV can be broken up and the... |
Stratospheric Ozone Depletion Global change AP Environmental Science Khan Academy.mp3 | So it's actually the fact that you have so much UV light up here that it reacts with oxygen that has raised to the stratosphere, and some of that gets formed into ozone. Now, ozone is very reactive, and it can be a little bit delicate. It has a very short half-life. It is way less stable than O2. And so it has to keep ... |
Stratospheric Ozone Depletion Global change AP Environmental Science Khan Academy.mp3 | It is way less stable than O2. And so it has to keep getting replenished in the atmosphere. And we also know that certain chemicals that we human beings have produced, in particular what's often known as chlorofluorocarbons, and that's just a fancy way of saying molecules that are hydrocarbons, so a bunch of carbons an... |
Stratospheric Ozone Depletion Global change AP Environmental Science Khan Academy.mp3 | And these molecules were generated in industrial applications, things like aerosol sprays. Used to have CFCs, but it turns out that CFCs will deplete the ozone layer. They'll come up from our little spray paint cans, and they'll interact with the ozone, and they will deplete it, which is not a good thing. Once again, i... |
Stratospheric Ozone Depletion Global change AP Environmental Science Khan Academy.mp3 | Once again, it will make us all more susceptible to things like cancer. Now, everything we've talked about so far is ozone in the stratosphere, but it turns out that ozone can actually also form lower in the atmosphere, in the place where we tend to spend our lives, in the troposphere. And when ozone is down there, it'... |
Stratospheric Ozone Depletion Global change AP Environmental Science Khan Academy.mp3 | And to understand why it might form down there, we need to understand the role, once again, that we're playing. Nitrous oxides are formed from automobile exhaust and coal-fired power plants. And when those, in the presence of UV light, and what's known as volatile organic compounds, which is just a fancy way of saying ... |
Stratospheric Ozone Depletion Global change AP Environmental Science Khan Academy.mp3 | And ozone, as I mentioned, is highly reactive. It can damage living tissue. It can damage our respiratory systems. So you don't want ozone around. So it's good in the upper atmosphere, and it is bad in the lower atmosphere. So I will leave you there. You got your primer on ozone. |
Nitrogen cycle Ecology Khan Academy.mp3 | Nitrogen often gets less attention than carbon or oxygen. But nitrogen is very important to life as well. And like carbon and oxygen, it cycles through our biosphere. Now one thing that's maybe surprising about nitrogen, if you haven't studied it much, is that it is very, very common in our atmosphere. 78% of our atmos... |
Nitrogen cycle Ecology Khan Academy.mp3 | Now one thing that's maybe surprising about nitrogen, if you haven't studied it much, is that it is very, very common in our atmosphere. 78% of our atmosphere is molecular nitrogen. So it's in the form of N2. So this right over here is molecular nitrogen. You have two nitrogen atoms covalently bonded to each other. Now... |
Nitrogen cycle Ecology Khan Academy.mp3 | So this right over here is molecular nitrogen. You have two nitrogen atoms covalently bonded to each other. Now unlike carbon, which can be directly fixed by plants, in the carbon cycle video we talk about how autotrophs like plants can take light energy and use that to fix carbon from the air into a solid form and sto... |
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