YouTube: | https://youtube.com/watch?v=kjZAHBMMKoU |
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View count: | 34,869 |
Likes: | 1,304 |
Comments: | 39 |
Duration: | 12:22 |
Uploaded: | 2024-05-14 |
Last sync: | 2024-09-05 13:30 |
Citation
Citation formatting is not guaranteed to be accurate. | |
MLA Full: | "How Animals Turn Resources Into Waste: The Poop Episode: Crash Course Biology #43." YouTube, uploaded by CrashCourse, 14 May 2024, www.youtube.com/watch?v=kjZAHBMMKoU. |
MLA Inline: | (CrashCourse, 2024) |
APA Full: | CrashCourse. (2024, May 14). How Animals Turn Resources Into Waste: The Poop Episode: Crash Course Biology #43 [Video]. YouTube. https://youtube.com/watch?v=kjZAHBMMKoU |
APA Inline: | (CrashCourse, 2024) |
Chicago Full: |
CrashCourse, "How Animals Turn Resources Into Waste: The Poop Episode: Crash Course Biology #43.", May 14, 2024, YouTube, 12:22, https://youtube.com/watch?v=kjZAHBMMKoU. |
Yep, this is the poop episode. Getting resources and getting rid of waste is so important, we have three whole systems dedicated to it! In this episode, we’ll learn how the respiratory system, digestive system, and urinary system work, and visit some other animals that process their resources in completely different (and sometimes totally wild) ways.
Introduction: C. diff 00:00
The Respiratory System 01:30
Ingestion & Digestion 03:53
Absorption & Propulsion 05:26
Defecation 08:25
The Urinary System 09:46
Review & Credits 10:49
This series was produced in collaboration with HHMI BioInteractive, committed to empowering educators and inspiring students with engaging, accessible, and quality classroom resources. Visit https://BioInteractive.org/CrashCourse for more information.
Check out our Biology playlist here: https://www.youtube.com/playlist?list=PL8dPuuaLjXtPW_ofbxdHNciuLoTRLPMgB
Watch this series in Spanish on our Crash Course en Español channel here: https://www.youtube.com/playlist?list=PLkcbA0DkuFjWQZzjwF6w_gUrE_5_d3vd3
Sources: https://docs.google.com/document/d/1GLDtAXE6ekg4Chk2qN3TYbNt0pJbyaHqTqRd6QY8pd4/edit?usp=sharing
***
Crash Course is on Patreon! You can support us directly by signing up at http://www.patreon.com/crashcourse
Thanks to the following patrons for their generous monthly contributions that help keep Crash Course free for everyone forever:
Leah H., David Fanska, Andrew Woods, DL Singfield, Ken Davidian, Stephen Akuffo, Toni Miles, Steve Segreto, Kyle & Katherine Callahan, Laurel Stevens, Burt Humburg, Perry Joyce, Scott Harrison, Mark & Susan Billian, Alan Bridgeman, Breanna Bosso, Matt Curls, Jennifer Killen, Jon Allen, Sarah & Nathan Catchings, team dorsey, Bernardo Garza, Trevin Beattie, Eric Koslow, Indija-ka Siriwardena, Jason Rostoker, Siobhán, Ken Penttinen, Nathan Taylor, Barrett & Laura Nuzum, Les Aker, William McGraw, Vaso, ClareG, Rizwan Kassim, Constance Urist, Alex Hackman, Pineapples of Solidarity, Katie Dean, Stephen McCandless, Wai Jack Sin, Ian Dundore, Caleb Weeks
__
Want to find Crash Course elsewhere on the internet?
Instagram - https://www.instagram.com/thecrashcourse/
Facebook - http://www.facebook.com/YouTubeCrashCourse
Twitter - http://www.twitter.com/TheCrashCourse
CC Kids: http://www.youtube.com/crashcoursekids
Introduction: C. diff 00:00
The Respiratory System 01:30
Ingestion & Digestion 03:53
Absorption & Propulsion 05:26
Defecation 08:25
The Urinary System 09:46
Review & Credits 10:49
This series was produced in collaboration with HHMI BioInteractive, committed to empowering educators and inspiring students with engaging, accessible, and quality classroom resources. Visit https://BioInteractive.org/CrashCourse for more information.
Check out our Biology playlist here: https://www.youtube.com/playlist?list=PL8dPuuaLjXtPW_ofbxdHNciuLoTRLPMgB
Watch this series in Spanish on our Crash Course en Español channel here: https://www.youtube.com/playlist?list=PLkcbA0DkuFjWQZzjwF6w_gUrE_5_d3vd3
Sources: https://docs.google.com/document/d/1GLDtAXE6ekg4Chk2qN3TYbNt0pJbyaHqTqRd6QY8pd4/edit?usp=sharing
***
Crash Course is on Patreon! You can support us directly by signing up at http://www.patreon.com/crashcourse
Thanks to the following patrons for their generous monthly contributions that help keep Crash Course free for everyone forever:
Leah H., David Fanska, Andrew Woods, DL Singfield, Ken Davidian, Stephen Akuffo, Toni Miles, Steve Segreto, Kyle & Katherine Callahan, Laurel Stevens, Burt Humburg, Perry Joyce, Scott Harrison, Mark & Susan Billian, Alan Bridgeman, Breanna Bosso, Matt Curls, Jennifer Killen, Jon Allen, Sarah & Nathan Catchings, team dorsey, Bernardo Garza, Trevin Beattie, Eric Koslow, Indija-ka Siriwardena, Jason Rostoker, Siobhán, Ken Penttinen, Nathan Taylor, Barrett & Laura Nuzum, Les Aker, William McGraw, Vaso, ClareG, Rizwan Kassim, Constance Urist, Alex Hackman, Pineapples of Solidarity, Katie Dean, Stephen McCandless, Wai Jack Sin, Ian Dundore, Caleb Weeks
__
Want to find Crash Course elsewhere on the internet?
Instagram - https://www.instagram.com/thecrashcourse/
Facebook - http://www.facebook.com/YouTubeCrashCourse
Twitter - http://www.twitter.com/TheCrashCourse
CC Kids: http://www.youtube.com/crashcoursekids
Ok point #1. So, there’s this bacteria called C. diff.
If it takes over too much of someone’s colon, it can cause fever, diarrhea, and cramps. Not a great time. But there are treatments, including… fecal transplants.
Yep. You heard that right. Doctors take feces from a patient with a healthy population of gut microbes, mix it with water, and spray it onto the walls of a sick person’s colon. All in the name of introducing some much-needed bacteria.
And sure, I know what you’re thinking: “Dr. Sammy! Why???” But there’s a larger point here.
Point #2: When we think about animals getting resources and getting rid of waste, we often just think about food. We consume things that provide nutrients on one end and ditch what isn’t needed on the other. But these systems are about more than that: they’re about keeping a body in balance. Which can include food, but also things like gases and bacteria. The more we know about how this balancing act works, the better we can maintain it, and develop treatments to help us when things get off-kilter. Even if that means spraying a feces solution into someone’s colon. Hi!
I’m Dr. Sammy, your friendly neighborhood entomologist. I hope you’re not eating lunch right now, because this is Crash Course Biology, and today we’re talking about poo. But you know what don’t stank?
This theme music. [THEME MUSIC]
All organisms need a way to get resources and dispose of waste. Vertebrates — animals with backbones — do this using the digestive system and the urinary system — so, eating and going to the bathroom. But there’s also a third, hugely important player: the respiratory system, which acquires oxygen and gets rid of carbon dioxide. Oxygen is one key ingredient in the reactions that get our cells energy, alongside the glucose we get from eating and digesting food. While animals like us can last without food and water for days, without O2… we can’t go for long. In fact, humans can rarely survive more than ten minutes without breathing oxygen.
Virtually all animals need some kind of respiratory system to breathe, though how they look and operate varies. Like, instead of using lungs to breathe air, many fish absorb oxygen from the water around them through their gills. After oxygen is breathed in, it has to make its way to cells where respiration takes place. In animals with lungs, the oxygen molecules automatically move from where there’s a bunch of oxygen, to where there isn’t much—the bloodstream.
This is a process called diffusion, and it’s similar to how the smell of fresh cookies starts in the kitchen and wafts into the studio while you’re trying to record a video… and… I… [Offline: Sammy as cookie monster graphic] At the same time, carbon dioxide is going the other way: There’s more of it in the bloodstream, so it’s diffusing from the blood to the lungs. And when you breathe out… there it goes. This whole process is called gas exchange. Now, despite what it feels like when you take a good, deep breath, lungs aren’t a pair of balloons in your chest. They’re more like sponges, with lots of little openings.
You can think of gas exchange like a busy grocery store checkout on a Saturday morning. If there’s only one register open, the line will get so long that it’ll start wrapping around the store. But if there are ten registers open, the lines will move much faster, and more people can get through. The same thing goes for lungs—more entry points means faster gas exchange. Overall, it can be easy to crown oxygen the MVP of this process. But both parts — getting oxygen in and getting carbon dioxide out — are equally important. We need some CO2 in our blood, but too much is toxic to cells. And too much oxygen in the blood can be poisonous, too. So, with both gases — as with most things — it’s all about balance.
While your lungs are working on oxygen and CO2, another system is trying to balance other stuff—sugars, proteins, fats, vitamins and more. It’s the digestive system! And there’s no better way to get to know it than to follow the avocado toast I had for breakfast. This delicious morning meal is about to go on a five-step journey through my digestive tract, also known as my alimentary canal.
And I can already check off step one: ingestion. I ate the avocado toast. Amazing. Love it! Can’t say enough about this part.
Next, almost immediately, digestion begins. Digestion is breaking food into smaller bits, either mechanically — like by chewing — or chemically, like with the enzymes in my saliva and stomach. And while digestion happens in the mouth, it also happens in the stomach and small intestine. The microbes living in your small intestine can help here too. Most vertebrates digest food the same way we do, though there are a few exceptions. Like, typically birds don’t have teeth, so they swallow their food whole. And then to break it down, the bird swallows rocks and holds them in part of its stomach called the gizzard.
The gizzard contracts and grinds those rocks around with the bird’s food to break it apart. So… birds are basically living garbage disposals. And, as we’ve come to expect by now, our friend the platypus does things to the beat of its own drum. Platypuses don’t have teeth or stomachs because of course they don’t. Food is ground up by plates in their jaws before passing more or less directly from their throat to their intestines.
Always have to one-up us, don't you pal? Now, whether you’re a bird, a platy-anomaly, or a human, step three in the digestive system is the same: absorption. See, it’s not enough for my avocado toast to have been chewed and dissolved into vaguely-nutritious goop. Those nutrients also have to get absorbed into my body. In absorption, the broken-down bits from digestion move from the digestive tract to the bloodstream.
Sometimes this happens through diffusion, like in the lungs. But sometimes, your cells need molecules to move toward an area where there’s already a lot of them. This is called active transport because it’s, well, active. It costs energy rather than happening automatically. It turns out most absorption doesn’t happen in the stomach, as you might imagine, but in the intestines.
Like with your lungs, your intestines have a lot of open cash registers. They’re long and wrinkly, with lots of folds and valleys that molecules pass through to enter the bloodstream. So after my toast breaks down a bit, its nutrients are absorbed by my intestines. The carbohydrates and B vitamins in the whole wheat bread, and the fat in the avocado mostly get absorbed in the small intestine, along with a little water.
Then the large intestine absorbs a few more nutrients and lots of water while it gathers anything I can’t digest. Once those nutrients enter the bloodstream, that blood heads over to the liver, where the nutrients are processed. Some of them are modified and stored to be used later. And if there are any toxic compounds, a lot of those can be inactivated in the liver, too. Most vertebrates use a system roughly like this one. We might not all have teeth or gizzards, but we all have small intestines that absorb nutrients. Meanwhile, our invertebrate cousins can be incredibly different.
Take a starfish, for example. It doesn’t have a lot of room in its body for a huge, clam-filled stomach. So, after it breaks apart a clam and is ready to chow down, it just vomits up its stomach.
The stomach shoots out of its mouth and into the clamshell, where it releases some juicy enzymes to break down the meal. Once that clam is a pile of goo, those nutrients get absorbed straight into the stomach, and the whole organ gets sucked back into the starfish’s body. In a way, it’s not all that different from what humans do. Our bodies digest food, too, and those nutrients get absorbed. Starfish just have a… unique way of doing it. Before we get to the final stop on our digestive journey, there’s been something happening to my toast in the background this whole time: propulsion. This is where food moves through the digestive tract.
Propulsion includes swallowing, but also peristalsis: the process where muscles move food along the digestive tract. Ever wonder about the sound you hear when your stomach is getting all gurgly? That’s peristalsis!
It’s so important that one of the first big things NASA tested when it sent people to space was whether or not peristalsis works when you’re weightless. And thankfully, it does! Peristalsis is so powerful that the muscles in our digestive systems work against gravity. Alright! So, from ingestion to digestion to absorption, we’ve officially followed my breakfast as it was propelled through my digestive system.
Now it’s time for one last, glorious step, the moment you’ve all been waiting for, the pride of the digestive system: defecation! Also known as getting rid of undigested and unabsorbed food. Or… pooping. The plops if you will. In humans, this begins in the large intestine, which includes the colon. The intestine forms a big blob of water, undigested food, bacteria from your digestive tract, and various other waste products that aren’t handled by your urinary system, which we’ll get to in a second.
And that blob is none other than feces, which then hangs out in your rectum until it’s time to make a grand exit. Like with anything, not all organisms defecate the same way we do. Take jellyfish for example. Many have only one main opening in their bodies, so effectively, they eat and poop with the same hole. And one type of jellyfish has an anus that only appears when it needs to go. An Anus ex Machina, for my fellow drama nerds. So yeah, in the animal kingdom, everybody poops and there’s no wrong way to do it.
Last but not least, we have the urinary system, which is the main way animals get rid of waste. The urinary system’s plumbing is made of several organs, including the bladder, which stores urine—the fluid that carries the waste products— until it’s a convenient time to pee. But the champions of this system are really the kidneys. Kidneys filter blood. They use both diffusion and active transport to remove waste products from it, as well as things your body has too much of, like sodium or water.
And the byproduct is urine! This means that when you pee, it’s not because water passed through your stomach and intestines and out the other end, like a baby-wets-a-lot doll. It’s because that water was absorbed through your intestines into your blood, and then was filtered out by your kidneys. And kidneys are amazing—they’re constantly communicating with different parts of the body to know how much of what stuff needs to be removed.
For example, kidneys release an enzyme called renin that helps regulate blood pressure and the amount of calcium in our bones. For living things, acquiring resources and getting rid of waste is an endless balancing act, whether it’s happening in the intestines, the lungs, or the kidneys. And after billions of years, animals in particular are pretty amazing at this, all things considered.
Sure, you can disrupt your gut bacteria with medications or a diet change. But with every breath you take and every piece of food you eat, your body is doing its best to keep you balanced. Every breath you take, every food you plate, probiotic shakes, and tummy aches we're balancing your stool. Next time, we’ll learn more about how animal bodies manage to stay organized, and what stops us from being a random mess of organs. See you then.
Peace! This series was produced in collaboration with HHMI BioInteractive. If you’re an educator, visit BioInteractive.org/CrashCourse for classroom resources and professional development related to the topics covered in this course. Thanks for watching this episode of Crash Course Biology which was filmed at our studio in Indianapolis, Indiana, and was made with the help of all these nice people. If you want to help keep Crash Course free for everyone, forever, you can join our community on Patreon.
If it takes over too much of someone’s colon, it can cause fever, diarrhea, and cramps. Not a great time. But there are treatments, including… fecal transplants.
Yep. You heard that right. Doctors take feces from a patient with a healthy population of gut microbes, mix it with water, and spray it onto the walls of a sick person’s colon. All in the name of introducing some much-needed bacteria.
And sure, I know what you’re thinking: “Dr. Sammy! Why???” But there’s a larger point here.
Point #2: When we think about animals getting resources and getting rid of waste, we often just think about food. We consume things that provide nutrients on one end and ditch what isn’t needed on the other. But these systems are about more than that: they’re about keeping a body in balance. Which can include food, but also things like gases and bacteria. The more we know about how this balancing act works, the better we can maintain it, and develop treatments to help us when things get off-kilter. Even if that means spraying a feces solution into someone’s colon. Hi!
I’m Dr. Sammy, your friendly neighborhood entomologist. I hope you’re not eating lunch right now, because this is Crash Course Biology, and today we’re talking about poo. But you know what don’t stank?
This theme music. [THEME MUSIC]
All organisms need a way to get resources and dispose of waste. Vertebrates — animals with backbones — do this using the digestive system and the urinary system — so, eating and going to the bathroom. But there’s also a third, hugely important player: the respiratory system, which acquires oxygen and gets rid of carbon dioxide. Oxygen is one key ingredient in the reactions that get our cells energy, alongside the glucose we get from eating and digesting food. While animals like us can last without food and water for days, without O2… we can’t go for long. In fact, humans can rarely survive more than ten minutes without breathing oxygen.
Virtually all animals need some kind of respiratory system to breathe, though how they look and operate varies. Like, instead of using lungs to breathe air, many fish absorb oxygen from the water around them through their gills. After oxygen is breathed in, it has to make its way to cells where respiration takes place. In animals with lungs, the oxygen molecules automatically move from where there’s a bunch of oxygen, to where there isn’t much—the bloodstream.
This is a process called diffusion, and it’s similar to how the smell of fresh cookies starts in the kitchen and wafts into the studio while you’re trying to record a video… and… I… [Offline: Sammy as cookie monster graphic] At the same time, carbon dioxide is going the other way: There’s more of it in the bloodstream, so it’s diffusing from the blood to the lungs. And when you breathe out… there it goes. This whole process is called gas exchange. Now, despite what it feels like when you take a good, deep breath, lungs aren’t a pair of balloons in your chest. They’re more like sponges, with lots of little openings.
You can think of gas exchange like a busy grocery store checkout on a Saturday morning. If there’s only one register open, the line will get so long that it’ll start wrapping around the store. But if there are ten registers open, the lines will move much faster, and more people can get through. The same thing goes for lungs—more entry points means faster gas exchange. Overall, it can be easy to crown oxygen the MVP of this process. But both parts — getting oxygen in and getting carbon dioxide out — are equally important. We need some CO2 in our blood, but too much is toxic to cells. And too much oxygen in the blood can be poisonous, too. So, with both gases — as with most things — it’s all about balance.
While your lungs are working on oxygen and CO2, another system is trying to balance other stuff—sugars, proteins, fats, vitamins and more. It’s the digestive system! And there’s no better way to get to know it than to follow the avocado toast I had for breakfast. This delicious morning meal is about to go on a five-step journey through my digestive tract, also known as my alimentary canal.
And I can already check off step one: ingestion. I ate the avocado toast. Amazing. Love it! Can’t say enough about this part.
Next, almost immediately, digestion begins. Digestion is breaking food into smaller bits, either mechanically — like by chewing — or chemically, like with the enzymes in my saliva and stomach. And while digestion happens in the mouth, it also happens in the stomach and small intestine. The microbes living in your small intestine can help here too. Most vertebrates digest food the same way we do, though there are a few exceptions. Like, typically birds don’t have teeth, so they swallow their food whole. And then to break it down, the bird swallows rocks and holds them in part of its stomach called the gizzard.
The gizzard contracts and grinds those rocks around with the bird’s food to break it apart. So… birds are basically living garbage disposals. And, as we’ve come to expect by now, our friend the platypus does things to the beat of its own drum. Platypuses don’t have teeth or stomachs because of course they don’t. Food is ground up by plates in their jaws before passing more or less directly from their throat to their intestines.
Always have to one-up us, don't you pal? Now, whether you’re a bird, a platy-anomaly, or a human, step three in the digestive system is the same: absorption. See, it’s not enough for my avocado toast to have been chewed and dissolved into vaguely-nutritious goop. Those nutrients also have to get absorbed into my body. In absorption, the broken-down bits from digestion move from the digestive tract to the bloodstream.
Sometimes this happens through diffusion, like in the lungs. But sometimes, your cells need molecules to move toward an area where there’s already a lot of them. This is called active transport because it’s, well, active. It costs energy rather than happening automatically. It turns out most absorption doesn’t happen in the stomach, as you might imagine, but in the intestines.
Like with your lungs, your intestines have a lot of open cash registers. They’re long and wrinkly, with lots of folds and valleys that molecules pass through to enter the bloodstream. So after my toast breaks down a bit, its nutrients are absorbed by my intestines. The carbohydrates and B vitamins in the whole wheat bread, and the fat in the avocado mostly get absorbed in the small intestine, along with a little water.
Then the large intestine absorbs a few more nutrients and lots of water while it gathers anything I can’t digest. Once those nutrients enter the bloodstream, that blood heads over to the liver, where the nutrients are processed. Some of them are modified and stored to be used later. And if there are any toxic compounds, a lot of those can be inactivated in the liver, too. Most vertebrates use a system roughly like this one. We might not all have teeth or gizzards, but we all have small intestines that absorb nutrients. Meanwhile, our invertebrate cousins can be incredibly different.
Take a starfish, for example. It doesn’t have a lot of room in its body for a huge, clam-filled stomach. So, after it breaks apart a clam and is ready to chow down, it just vomits up its stomach.
The stomach shoots out of its mouth and into the clamshell, where it releases some juicy enzymes to break down the meal. Once that clam is a pile of goo, those nutrients get absorbed straight into the stomach, and the whole organ gets sucked back into the starfish’s body. In a way, it’s not all that different from what humans do. Our bodies digest food, too, and those nutrients get absorbed. Starfish just have a… unique way of doing it. Before we get to the final stop on our digestive journey, there’s been something happening to my toast in the background this whole time: propulsion. This is where food moves through the digestive tract.
Propulsion includes swallowing, but also peristalsis: the process where muscles move food along the digestive tract. Ever wonder about the sound you hear when your stomach is getting all gurgly? That’s peristalsis!
It’s so important that one of the first big things NASA tested when it sent people to space was whether or not peristalsis works when you’re weightless. And thankfully, it does! Peristalsis is so powerful that the muscles in our digestive systems work against gravity. Alright! So, from ingestion to digestion to absorption, we’ve officially followed my breakfast as it was propelled through my digestive system.
Now it’s time for one last, glorious step, the moment you’ve all been waiting for, the pride of the digestive system: defecation! Also known as getting rid of undigested and unabsorbed food. Or… pooping. The plops if you will. In humans, this begins in the large intestine, which includes the colon. The intestine forms a big blob of water, undigested food, bacteria from your digestive tract, and various other waste products that aren’t handled by your urinary system, which we’ll get to in a second.
And that blob is none other than feces, which then hangs out in your rectum until it’s time to make a grand exit. Like with anything, not all organisms defecate the same way we do. Take jellyfish for example. Many have only one main opening in their bodies, so effectively, they eat and poop with the same hole. And one type of jellyfish has an anus that only appears when it needs to go. An Anus ex Machina, for my fellow drama nerds. So yeah, in the animal kingdom, everybody poops and there’s no wrong way to do it.
Last but not least, we have the urinary system, which is the main way animals get rid of waste. The urinary system’s plumbing is made of several organs, including the bladder, which stores urine—the fluid that carries the waste products— until it’s a convenient time to pee. But the champions of this system are really the kidneys. Kidneys filter blood. They use both diffusion and active transport to remove waste products from it, as well as things your body has too much of, like sodium or water.
And the byproduct is urine! This means that when you pee, it’s not because water passed through your stomach and intestines and out the other end, like a baby-wets-a-lot doll. It’s because that water was absorbed through your intestines into your blood, and then was filtered out by your kidneys. And kidneys are amazing—they’re constantly communicating with different parts of the body to know how much of what stuff needs to be removed.
For example, kidneys release an enzyme called renin that helps regulate blood pressure and the amount of calcium in our bones. For living things, acquiring resources and getting rid of waste is an endless balancing act, whether it’s happening in the intestines, the lungs, or the kidneys. And after billions of years, animals in particular are pretty amazing at this, all things considered.
Sure, you can disrupt your gut bacteria with medications or a diet change. But with every breath you take and every piece of food you eat, your body is doing its best to keep you balanced. Every breath you take, every food you plate, probiotic shakes, and tummy aches we're balancing your stool. Next time, we’ll learn more about how animal bodies manage to stay organized, and what stops us from being a random mess of organs. See you then.
Peace! This series was produced in collaboration with HHMI BioInteractive. If you’re an educator, visit BioInteractive.org/CrashCourse for classroom resources and professional development related to the topics covered in this course. Thanks for watching this episode of Crash Course Biology which was filmed at our studio in Indianapolis, Indiana, and was made with the help of all these nice people. If you want to help keep Crash Course free for everyone, forever, you can join our community on Patreon.