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And every now and then we'll also find small amounts of some other elements like this sulfur here in yellow. But the super interesting part here is that these are actually the same exact elements that make up most of the cells in your body, right? So you may notice on this right-hand side, the same colors as what we have on the left, right? So this is where the whole molecular lumber thing comes in. Our cells can take food and break it down into small building blocks, and then use those building blocks in order to build new structures in our body, right? So this is how we grow, right? This is how babies become adults.
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Food and energy in organisms Middle school biology Khan Academy.mp3
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So this is where the whole molecular lumber thing comes in. Our cells can take food and break it down into small building blocks, and then use those building blocks in order to build new structures in our body, right? So this is how we grow, right? This is how babies become adults. Turns out we actually are what we eat. It's pretty amazing. All right, but before we get too excited, let's bring it in, right?
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Food and energy in organisms Middle school biology Khan Academy.mp3
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This is how babies become adults. Turns out we actually are what we eat. It's pretty amazing. All right, but before we get too excited, let's bring it in, right? So let's switch gears for a second here to talk about the other side of things, because I told you before that food is like wood. And we can use wood to build new structures, sure. But when we need to, we can also burn wood to get energy, right?
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All right, but before we get too excited, let's bring it in, right? So let's switch gears for a second here to talk about the other side of things, because I told you before that food is like wood. And we can use wood to build new structures, sure. But when we need to, we can also burn wood to get energy, right? So we can start a campfire. And if we do, we know that we're going to get some energy in the form of light, right? We'll get some energy in the form of heat, and maybe some other things like sound.
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But when we need to, we can also burn wood to get energy, right? So we can start a campfire. And if we do, we know that we're going to get some energy in the form of light, right? We'll get some energy in the form of heat, and maybe some other things like sound. And food is actually the same way, right? So we can take those same food molecules that we broke down before to get building blocks, and instead use them as fuel to generate cellular energy. And then we can use that cellular energy to fuel all of the building that we just talked about.
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Food and energy in organisms Middle school biology Khan Academy.mp3
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We'll get some energy in the form of heat, and maybe some other things like sound. And food is actually the same way, right? So we can take those same food molecules that we broke down before to get building blocks, and instead use them as fuel to generate cellular energy. And then we can use that cellular energy to fuel all of the building that we just talked about. And likewise, if our cells work together, which they do, they can use this energy to do things like running, thinking, and all the other things that we humans do. All right, let's step back just one more time, because what we'll see is that these two processes that we've just described, right? So food is lumber and food is fuel, actually explains so much of life, right?
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And then we can use that cellular energy to fuel all of the building that we just talked about. And likewise, if our cells work together, which they do, they can use this energy to do things like running, thinking, and all the other things that we humans do. All right, let's step back just one more time, because what we'll see is that these two processes that we've just described, right? So food is lumber and food is fuel, actually explains so much of life, right? So this is not just us. Every living thing on this planet is doing this, right? So you feed your dog to fuel his or her molecular construction projects as well.
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Food and energy in organisms Middle school biology Khan Academy.mp3
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So food is lumber and food is fuel, actually explains so much of life, right? So this is not just us. Every living thing on this planet is doing this, right? So you feed your dog to fuel his or her molecular construction projects as well. So right there and then, we've already kind of answered our question from before, which reminder was, how do people go from small to big? Right? So what's happening is that this baby becomes an adult by eating food, milk, formula, gushy stuff, I don't know, whatever babies eat.
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Food and energy in organisms Middle school biology Khan Academy.mp3
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So you feed your dog to fuel his or her molecular construction projects as well. So right there and then, we've already kind of answered our question from before, which reminder was, how do people go from small to big? Right? So what's happening is that this baby becomes an adult by eating food, milk, formula, gushy stuff, I don't know, whatever babies eat. And some of the molecules in that food will be used as fuel to generate energy. And then some of that energy will be used to combine food molecules with molecules in the baby to build up a larger baby, aka an adult. All right, I hope that helps.
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Hey, have you ever seen this kind of plant before? It's called a dandelion. If you live in a tropical climate, it might be unfamiliar. But if you live in a more temperate zone, you'll probably recognize it as it's a very common plant. Dandelions make yellow flowers that develop into balls of these fluffy white seed heads that fly off the plant. This can happen by a gust of wind, by animals spreading them, or even by someone blowing on the plant. When this happens, its seeds fly into the air and land on new spots on the ground.
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Organism growth and the environment Middle school biology Khan Academy.mp3
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But if you live in a more temperate zone, you'll probably recognize it as it's a very common plant. Dandelions make yellow flowers that develop into balls of these fluffy white seed heads that fly off the plant. This can happen by a gust of wind, by animals spreading them, or even by someone blowing on the plant. When this happens, its seeds fly into the air and land on new spots on the ground. From there, the seeds can grow into new dandelions, starting the whole cycle over. But why do dandelions do this? Why do they turn into puffballs?
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When this happens, its seeds fly into the air and land on new spots on the ground. From there, the seeds can grow into new dandelions, starting the whole cycle over. But why do dandelions do this? Why do they turn into puffballs? Why are they yellow? If they don't have brains, how do they seem to know when to release their seeds? These are all complicated questions.
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Why do they turn into puffballs? Why are they yellow? If they don't have brains, how do they seem to know when to release their seeds? These are all complicated questions. But to begin answering them, we can talk about what influences the growth and development of dandelions and, in turn, all living things. So, what determines how our dandelion will grow? Its genes and its environment.
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Organism growth and the environment Middle school biology Khan Academy.mp3
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These are all complicated questions. But to begin answering them, we can talk about what influences the growth and development of dandelions and, in turn, all living things. So, what determines how our dandelion will grow? Its genes and its environment. Let's take a moment to review what genes are. Genes make up the hereditary material inside an organism's cells. Genes provide the information about what traits an organism has.
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Organism growth and the environment Middle school biology Khan Academy.mp3
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Its genes and its environment. Let's take a moment to review what genes are. Genes make up the hereditary material inside an organism's cells. Genes provide the information about what traits an organism has. So, the reason that our dandelion has yellow petals and develops fluffy white seed heads lies within its genes. Any influence genes have on the way an organism grows is called a genetic factor. So, if one dandelion has more seeds than another, as a result of which version of a certain gene it has, we can say that the difference in seed number is due to a genetic factor.
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Organism growth and the environment Middle school biology Khan Academy.mp3
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Genes provide the information about what traits an organism has. So, the reason that our dandelion has yellow petals and develops fluffy white seed heads lies within its genes. Any influence genes have on the way an organism grows is called a genetic factor. So, if one dandelion has more seeds than another, as a result of which version of a certain gene it has, we can say that the difference in seed number is due to a genetic factor. The other major influence on how our dandelion grows is its environment. But what makes up an organism's environment? The environment is the set of conditions an organism is exposed to during its life.
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So, if one dandelion has more seeds than another, as a result of which version of a certain gene it has, we can say that the difference in seed number is due to a genetic factor. The other major influence on how our dandelion grows is its environment. But what makes up an organism's environment? The environment is the set of conditions an organism is exposed to during its life. For our dandelion, this includes temperature, how much light and water it gets, and which nutrients are present in the soil where it grows. Any influence the environment has on an organism's growth is called an environmental factor. So, if one dandelion plant is exposed to more sunlight than another and grows bigger as a result, we can say that the difference is due to an environmental factor.
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Organism growth and the environment Middle school biology Khan Academy.mp3
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The environment is the set of conditions an organism is exposed to during its life. For our dandelion, this includes temperature, how much light and water it gets, and which nutrients are present in the soil where it grows. Any influence the environment has on an organism's growth is called an environmental factor. So, if one dandelion plant is exposed to more sunlight than another and grows bigger as a result, we can say that the difference is due to an environmental factor. But plants aren't the only living organisms that are motivated by these factors. Animals are also influenced by their genes and environment. For example, let's look at dogs.
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So, if one dandelion plant is exposed to more sunlight than another and grows bigger as a result, we can say that the difference is due to an environmental factor. But plants aren't the only living organisms that are motivated by these factors. Animals are also influenced by their genes and environment. For example, let's look at dogs. Dogs come in many different shapes, sizes, colors, and each have their own unique features. We can see this when looking at different breeds, like pugs, which are small with squishy faces, and golden retrievers, which are large with flowing locks of golden fur. These traits are largely determined by which genes each breed of dog has, or, in other words, by genetic factors.
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Organism growth and the environment Middle school biology Khan Academy.mp3
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For example, let's look at dogs. Dogs come in many different shapes, sizes, colors, and each have their own unique features. We can see this when looking at different breeds, like pugs, which are small with squishy faces, and golden retrievers, which are large with flowing locks of golden fur. These traits are largely determined by which genes each breed of dog has, or, in other words, by genetic factors. But dogs are also influenced by environmental factors, too. For instance, how much food they get as they grow helps determine their size, and what they learn from other dogs and from people help determine their behaviors, like when you teach your dog a new trick. And now you know how organisms are influenced by genetics and their environment when it comes to growth and development.
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These traits are largely determined by which genes each breed of dog has, or, in other words, by genetic factors. But dogs are also influenced by environmental factors, too. For instance, how much food they get as they grow helps determine their size, and what they learn from other dogs and from people help determine their behaviors, like when you teach your dog a new trick. And now you know how organisms are influenced by genetics and their environment when it comes to growth and development. Let's do a quick review of what you've learned today. First, there are two main factors that influence an organism's growth. These are genetic and environmental factors.
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Organism growth and the environment Middle school biology Khan Academy.mp3
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And now you know how organisms are influenced by genetics and their environment when it comes to growth and development. Let's do a quick review of what you've learned today. First, there are two main factors that influence an organism's growth. These are genetic and environmental factors. Genetic factors are the genes the organism gets from its parent or parents, while environmental factors are the conditions an organism is exposed to as it grows. These factors show that all living organisms have a couple things in common, even dogs and dandelions. So while our interactions with them may differ, like how you can't teach a dandelion to sit like you can with a dog, both organisms experience growth and development through their own unique genes and environments.
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So it seems like over time, these zebras should just be able to keep multiplying until they fill up all of this land, similar for the buffalo, similar for the antelope. Why don't we see that? Pause this video and think about that. So let's start by thinking about what any organism or a population of organisms or a community of populations need to survive. Most animals that live on the surface, like these animals, need air, especially oxygen. Plants need carbon dioxide from the air. They need water.
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So let's start by thinking about what any organism or a population of organisms or a community of populations need to survive. Most animals that live on the surface, like these animals, need air, especially oxygen. Plants need carbon dioxide from the air. They need water. They need a source of energy, which I will call food, or I could say it's energy here, because it's not always in the form of food as we might recognize it. And I guess we think really basically, they need space in which to exist. Now, as I mentioned, there seems to be a lot of space here for the animals, so that doesn't seem to be the resource that is limiting their growth.
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They need water. They need a source of energy, which I will call food, or I could say it's energy here, because it's not always in the form of food as we might recognize it. And I guess we think really basically, they need space in which to exist. Now, as I mentioned, there seems to be a lot of space here for the animals, so that doesn't seem to be the resource that is limiting their growth. So let's rule that out here. Now, it's also clear that it seems like there's a fairly large amount of air here, more than enough air for these populations to grow. So that doesn't seem to be a resource that's somehow putting a maximum on how many of these organisms there are.
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Now, as I mentioned, there seems to be a lot of space here for the animals, so that doesn't seem to be the resource that is limiting their growth. So let's rule that out here. Now, it's also clear that it seems like there's a fairly large amount of air here, more than enough air for these populations to grow. So that doesn't seem to be a resource that's somehow putting a maximum on how many of these organisms there are. It does not look like a limited resource or a limiting resource. Now, what about water? Well, water does seem interesting here because this watering hole does not seem like it's very deep.
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So that doesn't seem to be a resource that's somehow putting a maximum on how many of these organisms there are. It does not look like a limited resource or a limiting resource. Now, what about water? Well, water does seem interesting here because this watering hole does not seem like it's very deep. It does not seem like there's a lot of water here. So this one could be what we would call a limited resource that is limiting population. Maybe if they had more and more offspring, there just wouldn't be enough water for any member of a population.
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Well, water does seem interesting here because this watering hole does not seem like it's very deep. It does not seem like there's a lot of water here. So this one could be what we would call a limited resource that is limiting population. Maybe if they had more and more offspring, there just wouldn't be enough water for any member of a population. And then of course, the populations would be competing with each other as well because they all need the same water to drink. Now, what about food? Well, you might recognize that zebra or antelope or buffalo, they tend to graze on grasses.
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Maybe if they had more and more offspring, there just wouldn't be enough water for any member of a population. And then of course, the populations would be competing with each other as well because they all need the same water to drink. Now, what about food? Well, you might recognize that zebra or antelope or buffalo, they tend to graze on grasses. And there are some grasses over here, but we also see that a lot of the grass is dead or dried out, and there's just a lot of areas with dirt here. So it looks like the food and energy is also a limiting resource. And we have to remind ourselves there's populations of different types of grasses and why aren't they spreading more?
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Well, you might recognize that zebra or antelope or buffalo, they tend to graze on grasses. And there are some grasses over here, but we also see that a lot of the grass is dead or dried out, and there's just a lot of areas with dirt here. So it looks like the food and energy is also a limiting resource. And we have to remind ourselves there's populations of different types of grasses and why aren't they spreading more? Well, from the perspective of a plant, it looks like the air and space is for sure abundant and even energy in the form of sunlight is abundant based on this picture. So it's probably water is the limited resource, which is keeping us from having more plants and grasses in this picture. We could imagine a scenario in which it rains a lot.
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And we have to remind ourselves there's populations of different types of grasses and why aren't they spreading more? Well, from the perspective of a plant, it looks like the air and space is for sure abundant and even energy in the form of sunlight is abundant based on this picture. So it's probably water is the limited resource, which is keeping us from having more plants and grasses in this picture. We could imagine a scenario in which it rains a lot. There's a lot of water, water is abundant. Then all of the different types of populations of grasses are able to expand. And then there's more than enough food and water for these animals to keep reproducing.
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We could imagine a scenario in which it rains a lot. There's a lot of water, water is abundant. Then all of the different types of populations of grasses are able to expand. And then there's more than enough food and water for these animals to keep reproducing. In that case, space might become an issue. But the important thing to realize here is that all organisms need resources in order to survive and in order to multiply and reproduce. Populations of many different species are often competing for those resources, like the water here.
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And then there's more than enough food and water for these animals to keep reproducing. In that case, space might become an issue. But the important thing to realize here is that all organisms need resources in order to survive and in order to multiply and reproduce. Populations of many different species are often competing for those resources, like the water here. That will tend to put a limit on how much these populations can grow. And the limit on one population can affect another. As we said, if you had more water, you could have more grass, which will allow for more food and energy for these other populations.
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But the obvious question is, how do these species actually do that? What is the mechanism? Well, one of the major mechanisms is natural selection. So natural selection is all based on, at any given point in time, there is variation in a species. There are different traits that are expressed in different ways. And many times, a lot of those variations are fine, but then you could have environmental factors, which makes some of those traits more favorable than others. And if those traits are more favorable to be able to survive, to be able to get food, or to be able to reproduce, well, then the genes that code for those traits are more likely to be passed on generation after generation.
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So natural selection is all based on, at any given point in time, there is variation in a species. There are different traits that are expressed in different ways. And many times, a lot of those variations are fine, but then you could have environmental factors, which makes some of those traits more favorable than others. And if those traits are more favorable to be able to survive, to be able to get food, or to be able to reproduce, well, then the genes that code for those traits are more likely to be passed on generation after generation. And to make this very tangible, I will give you the example of the peppered moth, which is probably the most common example when people show evidence of natural selection. If you were to go to the mid-1800s in London, most of the peppered moths were the white-peppered moths. There were very few black-peppered moths, but there was variation.
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And if those traits are more favorable to be able to survive, to be able to get food, or to be able to reproduce, well, then the genes that code for those traits are more likely to be passed on generation after generation. And to make this very tangible, I will give you the example of the peppered moth, which is probably the most common example when people show evidence of natural selection. If you were to go to the mid-1800s in London, most of the peppered moths were the white-peppered moths. There were very few black-peppered moths, but there was variation. There would be some lighter ones, there would be some darker ones, and in between. Now, what's interesting is, between the mid-1800s and the late-1800s, you have the Industrial Revolution in London really hitting full gear, and so there was a lot of pollution in the air, and so a lot of the surfaces that the moths might rest on, like trees or the wall of a building, became darker and darker. So as where these moths could rest became darker and darker, what do you think might have happened?
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There were very few black-peppered moths, but there was variation. There would be some lighter ones, there would be some darker ones, and in between. Now, what's interesting is, between the mid-1800s and the late-1800s, you have the Industrial Revolution in London really hitting full gear, and so there was a lot of pollution in the air, and so a lot of the surfaces that the moths might rest on, like trees or the wall of a building, became darker and darker. So as where these moths could rest became darker and darker, what do you think might have happened? Well, some of you might guess. In this different environment now, as the environment has gradually changed, all of a sudden, having the traits that make you darker will be more favorable than they were even 30 or 40 or 50 years ago, and the white trait, which might have been okay in the mid-1800s, now all of a sudden makes these moths very obvious to see. So if there was a bird that was looking for lunch, it'd be very easy to pick up the white moths versus the black moths.
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So as where these moths could rest became darker and darker, what do you think might have happened? Well, some of you might guess. In this different environment now, as the environment has gradually changed, all of a sudden, having the traits that make you darker will be more favorable than they were even 30 or 40 or 50 years ago, and the white trait, which might have been okay in the mid-1800s, now all of a sudden makes these moths very obvious to see. So if there was a bird that was looking for lunch, it'd be very easy to pick up the white moths versus the black moths. And what we saw is actually, by the 1900s, most of the peppered moths in London were now darker in color. And so what you had happening generation after generation is variation in the moth color, but as the background environment became darker, the ones that were white-colored were easier to pick off by predators, and if they're picked off by a predator, they're definitely not reproducing and passing on their genes, and then the ones that were able to survive and pass on their genes were the darker moths. Now, what's been interesting over the last 50 or so years as environmental regulations have gone into effect and the air has started to clean up in places like London, you're seeing a return of the white-peppered moth because once again, the surfaces are no longer covered with soot, and so the variants that are lighter in color now have a decent chance of not being spotted, and if anything, now the darker ones might have a better chance of being spotted in this cleaner environment.
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So let's first talk about competition, which we have already talked about in other videos. In this picture here, do you see competition? Pause this video and think about that. Well, one limited resource that these animals need to survive is water. There's only a limited amount in this watering hole over here, and so you can imagine there is competition, not just amongst the members of a population, let's say between these zebra, but also between members of different species, between different populations in a community. The zebras are not just competing for water with each other, but also with these antelope, or with these buffalo over here. There might also be competition for food.
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Well, one limited resource that these animals need to survive is water. There's only a limited amount in this watering hole over here, and so you can imagine there is competition, not just amongst the members of a population, let's say between these zebra, but also between members of different species, between different populations in a community. The zebras are not just competing for water with each other, but also with these antelope, or with these buffalo over here. There might also be competition for food. It doesn't seem like there's a lot of grass to eat for all of these animals that like to graze on grass. So now let's move on to predation. Predation is when one organism eats another organism, usually to its own benefit.
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There might also be competition for food. It doesn't seem like there's a lot of grass to eat for all of these animals that like to graze on grass. So now let's move on to predation. Predation is when one organism eats another organism, usually to its own benefit. Do you see any predation happening here? Well, we don't see any of these animals chasing and killing each other. There might be other animals like lions offscreen that might hunt and kill and eat these animals right over here, but we know that these animals do eat grass, and as I said, it's not just about hunting and killing and eating from one animal to another.
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Predation is when one organism eats another organism, usually to its own benefit. Do you see any predation happening here? Well, we don't see any of these animals chasing and killing each other. There might be other animals like lions offscreen that might hunt and kill and eat these animals right over here, but we know that these animals do eat grass, and as I said, it's not just about hunting and killing and eating from one animal to another. It could be one organism to another. So the eating of the grass by these animals could actually be considered a form of predation, especially if it kills the grass. A more obvious form of predation is this brown bear here that has gotten the salmon out of this river.
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There might be other animals like lions offscreen that might hunt and kill and eat these animals right over here, but we know that these animals do eat grass, and as I said, it's not just about hunting and killing and eating from one animal to another. It could be one organism to another. So the eating of the grass by these animals could actually be considered a form of predation, especially if it kills the grass. A more obvious form of predation is this brown bear here that has gotten the salmon out of this river. It is clearly hunting and killing the salmon for its benefit, and it is likely that each of these bears are in competition with other bears for this limited resource. So last but not least, let's think a little bit about mutualism. Mutualism happens when two organisms benefit from interacting with each other.
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A more obvious form of predation is this brown bear here that has gotten the salmon out of this river. It is clearly hunting and killing the salmon for its benefit, and it is likely that each of these bears are in competition with other bears for this limited resource. So last but not least, let's think a little bit about mutualism. Mutualism happens when two organisms benefit from interacting with each other. Right over here, we have these starlings that actually hang out on this buffalo and pick lice and ticks off the buffalo's fur. This is mutualism because both parties benefit. These starlings are able to get food, and the buffalo no longer have these parasites, these things that are living off of the buffalo, sucking its blood out of its body, and also probably not itching as much.
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Mutualism happens when two organisms benefit from interacting with each other. Right over here, we have these starlings that actually hang out on this buffalo and pick lice and ticks off the buffalo's fur. This is mutualism because both parties benefit. These starlings are able to get food, and the buffalo no longer have these parasites, these things that are living off of the buffalo, sucking its blood out of its body, and also probably not itching as much. Now, based on how I just described it, there's not just mutualism here. There's also predation because these birds are actually hunting and killing the lice and the ticks on the buffalo's body. Now, related to being a predator is another word known as being a parasite, and that's what the lice and the ticks are doing, where they're sucking the blood of the buffalo, but they're not considered predators.
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These starlings are able to get food, and the buffalo no longer have these parasites, these things that are living off of the buffalo, sucking its blood out of its body, and also probably not itching as much. Now, based on how I just described it, there's not just mutualism here. There's also predation because these birds are actually hunting and killing the lice and the ticks on the buffalo's body. Now, related to being a predator is another word known as being a parasite, and that's what the lice and the ticks are doing, where they're sucking the blood of the buffalo, but they're not considered predators. They're more parasites because they don't kill the buffalo. They're just taking some resources away from it. So I'll leave you there.
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I love gardening. In fact, I have a huge garden with apples, blueberries, pumpkins, and tomatoes. I give my plants micronutrients, and maybe some fertilizer, but I don't give them food in the same way that I would give my dog, who eats multiple times a day. With plants, I just put them in the soil, water them regularly, and watch them grow. How do they do it? Well, they use a process called photosynthesis. Photosynthesis is a scientific term to describe how certain living things use energy from sunlight to live and grow.
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With plants, I just put them in the soil, water them regularly, and watch them grow. How do they do it? Well, they use a process called photosynthesis. Photosynthesis is a scientific term to describe how certain living things use energy from sunlight to live and grow. Many different kinds of plants, algae, and various single-celled organisms are able to carry out this amazing process. Today, let's describe photosynthesis using tomatoes. So here you see a young tomato plant, similar to the ones I have in my own garden.
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Photosynthesis in organisms Matter and energy in organisms Middle school biology Khan Academy.mp3
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Photosynthesis is a scientific term to describe how certain living things use energy from sunlight to live and grow. Many different kinds of plants, algae, and various single-celled organisms are able to carry out this amazing process. Today, let's describe photosynthesis using tomatoes. So here you see a young tomato plant, similar to the ones I have in my own garden. Let's name it Planty. First, let's start off by looking at Planty's immediate surroundings. The soil Planty is growing in contains water, and the air surrounding Planty contains molecules of carbon dioxide.
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Photosynthesis in organisms Matter and energy in organisms Middle school biology Khan Academy.mp3
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So here you see a young tomato plant, similar to the ones I have in my own garden. Let's name it Planty. First, let's start off by looking at Planty's immediate surroundings. The soil Planty is growing in contains water, and the air surrounding Planty contains molecules of carbon dioxide. These two compounds are the starting materials, or inputs, that Planty needs in order to carry out photosynthesis. Now, let's take a look at the weather forecast. Well, it looks like it's going to be a sunny day today, so when the sun shines on the earth, it sends out energy in the form of light.
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The soil Planty is growing in contains water, and the air surrounding Planty contains molecules of carbon dioxide. These two compounds are the starting materials, or inputs, that Planty needs in order to carry out photosynthesis. Now, let's take a look at the weather forecast. Well, it looks like it's going to be a sunny day today, so when the sun shines on the earth, it sends out energy in the form of light. This energy is essential for Planty to be able to carry out photosynthesis. Next, let's take a closer look at Planty, because Planty's cells are hiding a secret of their own. Inside Planty's cells are microscopic structures that help Planty carry out photosynthesis.
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Well, it looks like it's going to be a sunny day today, so when the sun shines on the earth, it sends out energy in the form of light. This energy is essential for Planty to be able to carry out photosynthesis. Next, let's take a closer look at Planty, because Planty's cells are hiding a secret of their own. Inside Planty's cells are microscopic structures that help Planty carry out photosynthesis. These structures are called chloroplasts. Chloroplasts contain green pigment molecules called chlorophyll. It is actually within these molecules that the sun's energy is captured for use during photosynthesis.
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Inside Planty's cells are microscopic structures that help Planty carry out photosynthesis. These structures are called chloroplasts. Chloroplasts contain green pigment molecules called chlorophyll. It is actually within these molecules that the sun's energy is captured for use during photosynthesis. Interestingly, chlorophyll is where leaves get their green color. To help you remember, think of chlorophyll like this. Chloro means green, and phyll means leaf.
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It is actually within these molecules that the sun's energy is captured for use during photosynthesis. Interestingly, chlorophyll is where leaves get their green color. To help you remember, think of chlorophyll like this. Chloro means green, and phyll means leaf. So when you put them together, you get green leaf. Okay, so now we know that carbon dioxide, water, and sunlight are required for photosynthesis to occur. And we know that in plants like Planty, photosynthesis happens in the chloroplasts with the help of chlorophyll.
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Photosynthesis in organisms Matter and energy in organisms Middle school biology Khan Academy.mp3
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Chloro means green, and phyll means leaf. So when you put them together, you get green leaf. Okay, so now we know that carbon dioxide, water, and sunlight are required for photosynthesis to occur. And we know that in plants like Planty, photosynthesis happens in the chloroplasts with the help of chlorophyll. Next, let's take a look at what happens during the process of photosynthesis itself. When the sunlight reaches Planty's chloroplast, its energy is used to rearrange the atoms in the carbon dioxide and water molecules through a series of chemical reactions. The outputs of these reactions are oxygen molecules and sugars.
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And we know that in plants like Planty, photosynthesis happens in the chloroplasts with the help of chlorophyll. Next, let's take a look at what happens during the process of photosynthesis itself. When the sunlight reaches Planty's chloroplast, its energy is used to rearrange the atoms in the carbon dioxide and water molecules through a series of chemical reactions. The outputs of these reactions are oxygen molecules and sugars. These sugars are vital to Planty's survival because they are used as a source of chemical energy that helps Planty live and grow. In other words, they're Planty's food. Planty can do a few things with the sugars made during photosynthesis.
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The outputs of these reactions are oxygen molecules and sugars. These sugars are vital to Planty's survival because they are used as a source of chemical energy that helps Planty live and grow. In other words, they're Planty's food. Planty can do a few things with the sugars made during photosynthesis. It can break the sugars down to get usable energy right away, or it can store the sugar molecules for later use. If Planty stores the sugar molecules, it can then use them as a source of energy in the future. This means that Planty can grow even when the sun isn't shining.
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Planty can do a few things with the sugars made during photosynthesis. It can break the sugars down to get usable energy right away, or it can store the sugar molecules for later use. If Planty stores the sugar molecules, it can then use them as a source of energy in the future. This means that Planty can grow even when the sun isn't shining. Planty can also use the sugar molecules to build larger molecules, such as cellulose, that make up the structure of Planty itself. In this way, Planty can grow bigger and bigger with very little help from me, all thanks to the process of photosynthesis. Planty's other output, oxygen, is released into the atmosphere.
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This means that Planty can grow even when the sun isn't shining. Planty can also use the sugar molecules to build larger molecules, such as cellulose, that make up the structure of Planty itself. In this way, Planty can grow bigger and bigger with very little help from me, all thanks to the process of photosynthesis. Planty's other output, oxygen, is released into the atmosphere. This is really cool because it provides organisms in the ecosystem, including us, with oxygen. So thanks, Planty, and other photosynthetic organisms, for giving us the oxygen we need to breathe. And that, my friends, is photosynthesis.
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Planty's other output, oxygen, is released into the atmosphere. This is really cool because it provides organisms in the ecosystem, including us, with oxygen. So thanks, Planty, and other photosynthetic organisms, for giving us the oxygen we need to breathe. And that, my friends, is photosynthesis. So next time you're in a garden, I want you to think about this. All the plant structures you can see, such as stems, leaves, and even the fruits and vegetables that we eat, are made up mostly of the atoms that were once a part of the starting materials of photosynthesis. With the help of a little sunlight, the plants made their own food and grew bigger, taking CO2 out of the atmosphere and releasing oxygen back in for us to breathe.
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We've already talked about reproductive success in other videos. It's related to the number of offspring an organism can have in its lifetime. And so in this video, we're going to think about strategies that plants use for reproductive success. A plant that has more surviving offspring has a higher reproductive success. So one major strategy that plants use to increase their chances of reproduction is by leveraging animals for pollination. You have seen pollination. This is a picture of a bee gathering nectar from this flower, but as it gathers that nectar, pollen also gets attached to that bee.
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A plant that has more surviving offspring has a higher reproductive success. So one major strategy that plants use to increase their chances of reproduction is by leveraging animals for pollination. You have seen pollination. This is a picture of a bee gathering nectar from this flower, but as it gathers that nectar, pollen also gets attached to that bee. So as that bee goes from flower to flower, from plant to plant, it's able to pollinate. It's able to take pollen from one plant and give it to another plant, allowing for that genetic mixing to occur and also to then have more plant reproduction. Now, once a plant is able to reproduce, we also need to think about how viable its offspring are going to be.
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This is a picture of a bee gathering nectar from this flower, but as it gathers that nectar, pollen also gets attached to that bee. So as that bee goes from flower to flower, from plant to plant, it's able to pollinate. It's able to take pollen from one plant and give it to another plant, allowing for that genetic mixing to occur and also to then have more plant reproduction. Now, once a plant is able to reproduce, we also need to think about how viable its offspring are going to be. Are they in conditions where they are likely to succeed in living and then reproducing themselves? And here, a common strategy, or at least a category of strategies that plants use are known as seed dispersal. And it's really just trying to get the seeds in as many places as possible, potentially far away from the plant itself to increase the chances that more of the seeds are going to be in places that are nutrient-rich where they can survive.
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Now, once a plant is able to reproduce, we also need to think about how viable its offspring are going to be. Are they in conditions where they are likely to succeed in living and then reproducing themselves? And here, a common strategy, or at least a category of strategies that plants use are known as seed dispersal. And it's really just trying to get the seeds in as many places as possible, potentially far away from the plant itself to increase the chances that more of the seeds are going to be in places that are nutrient-rich where they can survive. And once again, you have likely seen this. This is a dandelion plant. And when a strong wind blows, these dandelion seeds catch the wind because they have these structures which are not that aerodynamic, which pull the seeds along and can transport them for even miles and miles.
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And it's really just trying to get the seeds in as many places as possible, potentially far away from the plant itself to increase the chances that more of the seeds are going to be in places that are nutrient-rich where they can survive. And once again, you have likely seen this. This is a dandelion plant. And when a strong wind blows, these dandelion seeds catch the wind because they have these structures which are not that aerodynamic, which pull the seeds along and can transport them for even miles and miles. Many of these seeds aren't going to end up in useful places, but some of them might. And they might be in places where the future dandelion offspring are more likely to survive and then reproduce themselves. But seed dispersal also gets the help of animals.
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And when a strong wind blows, these dandelion seeds catch the wind because they have these structures which are not that aerodynamic, which pull the seeds along and can transport them for even miles and miles. Many of these seeds aren't going to end up in useful places, but some of them might. And they might be in places where the future dandelion offspring are more likely to survive and then reproduce themselves. But seed dispersal also gets the help of animals. This right over here is a picture of a bird eating fruit from a plant. And as that bird flies away and munches on that fruit, that seed might be dispersed. It might be thrown down hundreds of yards or even miles away from the original plant.
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But seed dispersal also gets the help of animals. This right over here is a picture of a bird eating fruit from a plant. And as that bird flies away and munches on that fruit, that seed might be dispersed. It might be thrown down hundreds of yards or even miles away from the original plant. In many cases, you might eat a fruit, and I am saying you because we do this ourselves. You might eat, say, a watermelon or a papaya and a couple of seeds go down while you ate it. And then later on, you or some other animal might poop it someplace where it might be a good place for that watermelon plant or that papaya plant to grow.
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It might be thrown down hundreds of yards or even miles away from the original plant. In many cases, you might eat a fruit, and I am saying you because we do this ourselves. You might eat, say, a watermelon or a papaya and a couple of seeds go down while you ate it. And then later on, you or some other animal might poop it someplace where it might be a good place for that watermelon plant or that papaya plant to grow. So this was just an overview of some of the strategies that plants use. But it's important to realize that throughout nature, we see this idea of reproductive success over and over again and in animals, behaviors, or strategies for reproductive success. And here we saw plants, strategies for reproductive success.
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We know that when this puppy grows up, he will have a healthy weight of about 70 pounds, he will love to play fetch, and enjoy snuggles with his human family. We know this because these traits are typical of his breed, Labradors. But where do these traits come from? In this video, we're going to find out. But first, let's start at the beginning. What exactly are traits? Traits are specific, observable characteristics.
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In this video, we're going to find out. But first, let's start at the beginning. What exactly are traits? Traits are specific, observable characteristics. They can be physical, like our puppy's eye color. They can be behavioral, such as a dog being more or less aggressive towards strangers. Or they can be health-related, such as a dog's risk of developing a certain disease.
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Traits are specific, observable characteristics. They can be physical, like our puppy's eye color. They can be behavioral, such as a dog being more or less aggressive towards strangers. Or they can be health-related, such as a dog's risk of developing a certain disease. Traits are passed from parents to offspring. This is why our puppy looks so similar to his parents, who were also Labradors. But how does this occur?
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Or they can be health-related, such as a dog's risk of developing a certain disease. Traits are passed from parents to offspring. This is why our puppy looks so similar to his parents, who were also Labradors. But how does this occur? Well, traits are passed on from one generation to the next through the inheritance of genes. Genes are pieces of hereditary material that are passed from parents to offspring. Genes are found inside of an organism's cells as part of structures called chromosomes.
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But how does this occur? Well, traits are passed on from one generation to the next through the inheritance of genes. Genes are pieces of hereditary material that are passed from parents to offspring. Genes are found inside of an organism's cells as part of structures called chromosomes. In multicellular organisms, chromosomes are found inside the cell nucleus. Chromosomes are often shown as X-shaped structures, like this one. Each chromosome is a structure that contains one long molecule of DNA, which stands for deoxyribonucleic acid, or DNA for short.
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Genes are found inside of an organism's cells as part of structures called chromosomes. In multicellular organisms, chromosomes are found inside the cell nucleus. Chromosomes are often shown as X-shaped structures, like this one. Each chromosome is a structure that contains one long molecule of DNA, which stands for deoxyribonucleic acid, or DNA for short. Here's a model showing a small stretch of a DNA molecule. You can see that it's made up of lots of different atoms, represented by these colored balls. The DNA molecule in a chromosome is like this, but much, much longer.
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Each chromosome is a structure that contains one long molecule of DNA, which stands for deoxyribonucleic acid, or DNA for short. Here's a model showing a small stretch of a DNA molecule. You can see that it's made up of lots of different atoms, represented by these colored balls. The DNA molecule in a chromosome is like this, but much, much longer. A chromosome's DNA molecule is coiled up in an organized way. This diagram shows what the DNA would look like if it were stretched out. This allows us to see where a chromosome's genes are located.
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The DNA molecule in a chromosome is like this, but much, much longer. A chromosome's DNA molecule is coiled up in an organized way. This diagram shows what the DNA would look like if it were stretched out. This allows us to see where a chromosome's genes are located. Genes are specific stretches of a chromosome's DNA molecule. Each chromosome's DNA can contain hundreds or even thousands of genes. And in multicellular organisms, each cell contains multiple chromosomes.
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This allows us to see where a chromosome's genes are located. Genes are specific stretches of a chromosome's DNA molecule. Each chromosome's DNA can contain hundreds or even thousands of genes. And in multicellular organisms, each cell contains multiple chromosomes. It's the collection of genes and chromosomes that contain the information about all of an organism's inherited traits. Like our puppy here, his chromosomes contain thousands of genes that help him determine his coat color, eye color, and all the other traits he inherited from his parents. So, our puppy must have one or more genes that cause him to have black fur.
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And in multicellular organisms, each cell contains multiple chromosomes. It's the collection of genes and chromosomes that contain the information about all of an organism's inherited traits. Like our puppy here, his chromosomes contain thousands of genes that help him determine his coat color, eye color, and all the other traits he inherited from his parents. So, our puppy must have one or more genes that cause him to have black fur. If he had been born with different versions of the fur color genes, he may have had yellow or brown fur. Heck, maybe one day someone will figure out how to change a puppy's DNA so that he has pink fur. And who knows, maybe you'll be the geneticist to make it happen!
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Have you ever thought about how incredible the human body is? For example, just to name a few things that your body's already been doing today, you're using your lungs to take breaths in and out, your heart's beating without stopping, and your brain is coordinating your body's functions and at the same time, helping you understand this video. All these body parts are made up of cells, which, as you might remember, are the smallest units of life. And it's so amazing that trillions of cells, without thoughts or intentions of their own, can come together to form something as complex as the human body. To help us understand how this occurs, we have to understand how the body is organized. The human body has a hierarchical organization, meaning it's made up of nested layers, each one more complex than the last. In this case, four different layers make up this hierarchy.
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And it's so amazing that trillions of cells, without thoughts or intentions of their own, can come together to form something as complex as the human body. To help us understand how this occurs, we have to understand how the body is organized. The human body has a hierarchical organization, meaning it's made up of nested layers, each one more complex than the last. In this case, four different layers make up this hierarchy. Cells, which make up tissues, tissues, which make up organs, organs, which make up organ systems, and finally, organ systems, which help the human body function as a whole. So let's start with cells and tissues. Cells are the smallest unit of life and the most basic level of organization in the human body.
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In this case, four different layers make up this hierarchy. Cells, which make up tissues, tissues, which make up organs, organs, which make up organ systems, and finally, organ systems, which help the human body function as a whole. So let's start with cells and tissues. Cells are the smallest unit of life and the most basic level of organization in the human body. In the human body, not all cells look or work the same. Instead, they're specialized to carry out different functions. After cells, the next level of organization is tissues.
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Cells are the smallest unit of life and the most basic level of organization in the human body. In the human body, not all cells look or work the same. Instead, they're specialized to carry out different functions. After cells, the next level of organization is tissues. A tissue is a collection of similar, specialized cells. And all of the cells that make up a tissue are like a team. They work together to ensure the tissue works properly.
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After cells, the next level of organization is tissues. A tissue is a collection of similar, specialized cells. And all of the cells that make up a tissue are like a team. They work together to ensure the tissue works properly. For instance, this image shows a section of the type of epithelial tissue that lines the inside of your mouth. This particular tissue is made up of epithelial cells, which are specialized to help protect your mouth from wear and tear. So the next time you're eating a pointy tortilla chip, remember how important this epithelial tissue is.
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They work together to ensure the tissue works properly. For instance, this image shows a section of the type of epithelial tissue that lines the inside of your mouth. This particular tissue is made up of epithelial cells, which are specialized to help protect your mouth from wear and tear. So the next time you're eating a pointy tortilla chip, remember how important this epithelial tissue is. Next up are organs and organ systems. So organs are structures that are made up of multiple different types of tissues, which all work together to help the organ function. And an organ system is a group of organs that work together to carry out complex functions for the body.
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So the next time you're eating a pointy tortilla chip, remember how important this epithelial tissue is. Next up are organs and organ systems. So organs are structures that are made up of multiple different types of tissues, which all work together to help the organ function. And an organ system is a group of organs that work together to carry out complex functions for the body. For instance, the lungs, shown here in the diagram, are made up of several tissue types that help them expand and contract. These tissue types include epithelial tissue, which is the same type of tissue we talked about earlier in the mouth, and connective tissue. And these tissues work together so that the lungs can carry out their role in the respiratory system, which is the organ system that allows us to respire, or breathe.
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Organization in the human body Cells and organisms Middle school biology Khan Academy.mp3
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And an organ system is a group of organs that work together to carry out complex functions for the body. For instance, the lungs, shown here in the diagram, are made up of several tissue types that help them expand and contract. These tissue types include epithelial tissue, which is the same type of tissue we talked about earlier in the mouth, and connective tissue. And these tissues work together so that the lungs can carry out their role in the respiratory system, which is the organ system that allows us to respire, or breathe. The respiratory system is made up of multiple organs, including the lungs, the trachea, the nose, and the diaphragm. When we breathe, our diaphragm, which is this muscle right here, contracts. Air is pulled through our nose and trachea and into our lungs.
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And these tissues work together so that the lungs can carry out their role in the respiratory system, which is the organ system that allows us to respire, or breathe. The respiratory system is made up of multiple organs, including the lungs, the trachea, the nose, and the diaphragm. When we breathe, our diaphragm, which is this muscle right here, contracts. Air is pulled through our nose and trachea and into our lungs. Here, gas exchange happens, and our body is taken oxygen and get rid of carbon dioxide. Then our diaphragm relaxes and we exhale. The respiratory system and other organ systems in the body carry out specific functions, but work together to keep us alive.
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Organization in the human body Cells and organisms Middle school biology Khan Academy.mp3
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Air is pulled through our nose and trachea and into our lungs. Here, gas exchange happens, and our body is taken oxygen and get rid of carbon dioxide. Then our diaphragm relaxes and we exhale. The respiratory system and other organ systems in the body carry out specific functions, but work together to keep us alive. And they do this mostly without us even realizing it. So it might get a little tricky to remember how all four levels of organization, cells, tissues, organs, and organ systems relate to each other. I like to think of these four different levels almost like the Russian nesting dolls that fit one inside another, with cells being the smallest doll on the inside.
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Organization in the human body Cells and organisms Middle school biology Khan Academy.mp3
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The respiratory system and other organ systems in the body carry out specific functions, but work together to keep us alive. And they do this mostly without us even realizing it. So it might get a little tricky to remember how all four levels of organization, cells, tissues, organs, and organ systems relate to each other. I like to think of these four different levels almost like the Russian nesting dolls that fit one inside another, with cells being the smallest doll on the inside. So cells make up tissues, tissues make up organs, and organs make up organ systems. All of these components come together to make up the human body. So I hope you've learned more about how our body's organization helps us thrive and stay alive.
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Organization in the human body Cells and organisms Middle school biology Khan Academy.mp3
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Take a guess. 100? 1000? More? Well, biologists have estimated that there are at least 10,000 different species of birds all around the world. And some biologists think that there are even more, up to 18,000 different species. Birds are incredibly diverse.
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https%3A%2F%2Fcdn.kastatic.org%2Fka-youtube-converted%2Fi3sdIHaa4jQ.mp4%2Fi3sdIHaa4jQ.mp4%23t%3D0.mp3
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More? Well, biologists have estimated that there are at least 10,000 different species of birds all around the world. And some biologists think that there are even more, up to 18,000 different species. Birds are incredibly diverse. Think about the differences between an eagle, a parrot, a hummingbird, a duck, and a penguin. Some of them are small and some are big. And take a look at the differences in their beaks or bills and their feathers.
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https%3A%2F%2Fcdn.kastatic.org%2Fka-youtube-converted%2Fi3sdIHaa4jQ.mp4%2Fi3sdIHaa4jQ.mp4%23t%3D0.mp3
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Birds are incredibly diverse. Think about the differences between an eagle, a parrot, a hummingbird, a duck, and a penguin. Some of them are small and some are big. And take a look at the differences in their beaks or bills and their feathers. And not all of these birds can fly either. Penguins use their wings like flippers to swim underwater. Collectively, these 10,000 plus different species of birds are a product of evolution, which is the change in heritable traits that occurs in a group of organisms over many generations.
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https%3A%2F%2Fcdn.kastatic.org%2Fka-youtube-converted%2Fi3sdIHaa4jQ.mp4%2Fi3sdIHaa4jQ.mp4%23t%3D0.mp3
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And take a look at the differences in their beaks or bills and their feathers. And not all of these birds can fly either. Penguins use their wings like flippers to swim underwater. Collectively, these 10,000 plus different species of birds are a product of evolution, which is the change in heritable traits that occurs in a group of organisms over many generations. But what are these heritable traits exactly? Heritable traits are those that are passed from parents to offspring via genes. And they include things like the colorful patterns and plumage, or the webbing or toes and claws of bird feet.
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https%3A%2F%2Fcdn.kastatic.org%2Fka-youtube-converted%2Fi3sdIHaa4jQ.mp4%2Fi3sdIHaa4jQ.mp4%23t%3D0.mp3
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Collectively, these 10,000 plus different species of birds are a product of evolution, which is the change in heritable traits that occurs in a group of organisms over many generations. But what are these heritable traits exactly? Heritable traits are those that are passed from parents to offspring via genes. And they include things like the colorful patterns and plumage, or the webbing or toes and claws of bird feet. And even though offspring inherit traits from their parents and look pretty similar to them, over many, many generations, these heritable traits can change. Evolution is made possible by genetic variation or differences in genes within a population. Genes are passed from parents to offspring and they affect how an organism develops, how it functions, and even how it looks.
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https%3A%2F%2Fcdn.kastatic.org%2Fka-youtube-converted%2Fi3sdIHaa4jQ.mp4%2Fi3sdIHaa4jQ.mp4%23t%3D0.mp3
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And they include things like the colorful patterns and plumage, or the webbing or toes and claws of bird feet. And even though offspring inherit traits from their parents and look pretty similar to them, over many, many generations, these heritable traits can change. Evolution is made possible by genetic variation or differences in genes within a population. Genes are passed from parents to offspring and they affect how an organism develops, how it functions, and even how it looks. Genes can come in different forms or alleles, which can lead to different versions of a trait. For example, in city pigeons, also called rock doves, which you might see flying around, different alleles cause different eye colors such as orange, black, and white. Genetic variation causes organisms within a population to have a range of traits, like differences in plumage or eye color.
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https%3A%2F%2Fcdn.kastatic.org%2Fka-youtube-converted%2Fi3sdIHaa4jQ.mp4%2Fi3sdIHaa4jQ.mp4%23t%3D0.mp3
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Genes are passed from parents to offspring and they affect how an organism develops, how it functions, and even how it looks. Genes can come in different forms or alleles, which can lead to different versions of a trait. For example, in city pigeons, also called rock doves, which you might see flying around, different alleles cause different eye colors such as orange, black, and white. Genetic variation causes organisms within a population to have a range of traits, like differences in plumage or eye color. Genetic variation can come from lots of different sources, one of which is through sexual reproduction. This type of reproduction causes offspring to have different sets of traits compared to their parents because they receive genetic material from both of their parents. In other words, the offspring aren't an exact genetic copy of either parent.
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https%3A%2F%2Fcdn.kastatic.org%2Fka-youtube-converted%2Fi3sdIHaa4jQ.mp4%2Fi3sdIHaa4jQ.mp4%23t%3D0.mp3
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Genetic variation causes organisms within a population to have a range of traits, like differences in plumage or eye color. Genetic variation can come from lots of different sources, one of which is through sexual reproduction. This type of reproduction causes offspring to have different sets of traits compared to their parents because they receive genetic material from both of their parents. In other words, the offspring aren't an exact genetic copy of either parent. In this example of rock doves, parents carry different alleles that affect their plumage, and in turn, their offspring can inherit different sets of traits and may look quite different from their parents. Now, let's take a look at that dove example with the plumage differences and think about it at the population level with lots of doves. You can imagine that those plumage traits can change over many, many generations of parents and offspring in a large population.
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https%3A%2F%2Fcdn.kastatic.org%2Fka-youtube-converted%2Fi3sdIHaa4jQ.mp4%2Fi3sdIHaa4jQ.mp4%23t%3D0.mp3
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In other words, the offspring aren't an exact genetic copy of either parent. In this example of rock doves, parents carry different alleles that affect their plumage, and in turn, their offspring can inherit different sets of traits and may look quite different from their parents. Now, let's take a look at that dove example with the plumage differences and think about it at the population level with lots of doves. You can imagine that those plumage traits can change over many, many generations of parents and offspring in a large population. You might see new traits appear, like different colors or different patterns and feathers, or existing traits like dark colors may become more or less common. When this type of change occurs, or any change in heritable traits, that group of organisms has evolved. Over many generations, small differences and traits between generations can add up, and over time, over thousands to millions of years, evolution can give rise to new types of organisms.
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https%3A%2F%2Fcdn.kastatic.org%2Fka-youtube-converted%2Fi3sdIHaa4jQ.mp4%2Fi3sdIHaa4jQ.mp4%23t%3D0.mp3
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You can imagine that those plumage traits can change over many, many generations of parents and offspring in a large population. You might see new traits appear, like different colors or different patterns and feathers, or existing traits like dark colors may become more or less common. When this type of change occurs, or any change in heritable traits, that group of organisms has evolved. Over many generations, small differences and traits between generations can add up, and over time, over thousands to millions of years, evolution can give rise to new types of organisms. For example, over many generations, one population can evolve into two different species, like the rock dove and the hill pigeon. Even though these two types of birds look pretty similar to one another, they are distinct species that have been changing along independent evolutionary paths for about a million years. Over the billions of years that life has existed on Earth, evolution has given rise to the amazing diversity of organisms on our planet.
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https%3A%2F%2Fcdn.kastatic.org%2Fka-youtube-converted%2Fi3sdIHaa4jQ.mp4%2Fi3sdIHaa4jQ.mp4%23t%3D0.mp3
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Hi everyone! In this video we are going to be talking about one of the most fascinating and complex features of life on Earth. Cells. But before we do, I'd like to take us way back to when I was a little kid. Now, I know that for me at least, I had a great time playing with toy building blocks and creating things out of them. I used blocks of different shapes and sizes to make all kinds of things like houses, cars, even spaceships and airplanes. You're probably thinking, what does this have to do with cells?
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Cells and Organisms Middle school biology Khan Academy.mp3
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