Exploring Natural World and Ecosystems

In the first few weeks of this class, we're going to start out talking about the natural world and how it functions. What does science tell us about the natural world and how it functions? So we'll start with the concept of biosphere. That's basically the largest category that we can look at when we're looking at life on Earth. And the biosphere is basically defined as the region of Earth occupied by life. And it's composed of three different spheres. The atmosphere is the zone of air that surrounds earth that supports and contains life. The lithosphere is the zone, the terrestrial zone. It's made up of the earth's crust and of course that supports and contains life. And then we have the hydrosphere which is the zone of water on earth that supports and contains life. The biosphere is made up of non-living components. We call those abiotic components. A means non, and of course, bio means life. So these are the non-living components of the biosphere that, of course, very much so influence and affect the living components. So there's some examples of abiotic components here on the slide. Fire, the presence of fire, of course, could greatly affect life on Earth. Climate things like precipitation and temperature greatly affect life on Earth. Topography, which is the slope of the landscape. Soil type. Try to think of some other abiotic components of the biosphere that affect life on Earth. Things like maybe the amount of sunlight available, maybe the amount of wind, seasonality. All of these things are abiotic components of the biosphere that greatly influence. what species occur where, and how well different species do on Earth. Then of course there are the biotic components or the living components or what I like to call the critters that make up the biosphere. We'll spend a lot of time talking about these and the different things that influence their success and reproduction on Earth. When you study the natural world, the first thing you have to ask yourself is of what scale of study am I going to look at the natural world? For example, am I interested in biosphere level questions? For example, how is the climate changing on earth and how is that influencing life on earth? That would be a biosphere level question. Or are you interested in a particular location and how species are interacting with their environments in that one location? Are you interested in just one particular species? in a particular spot and you just want to ask questions about it. So you have to determine what level of scale or what category of organisms you're going to look at. And in this class, the level of scale that we're going to be most concerned with is the ecosystem level. So an ecosystem is defined as a group of different species in a given area. So we're not just looking at one species here, we're looking at a group of different species in a given area. And when you do an ecosystem study, you're looking at not only interactions between the living things, but interactions between the living things and their environment. So there is that abiotic component to ecosystem studies. So this part about an ecosystem is defined as being stable enough so that nutrients, cycle and energy flows. You might not know what that quite means yet. We are going to talk about both those things, nutrients, cycling, and energy flowing, but just realize at this point that an ecosystem is a system that's going to be around for a while. It's not just there for a few minutes. There is some sustainability to it. For example, a puddle in a middle of a parking lot probably wouldn't be considered an ecosystem. Now, would it not be because... Consider it an ecosystem because there's no life in it, because there's no species living in that puddle? No, there's probably a lot of things living in that puddle, even if it's there for just a few minutes. If you took a sample of the water and looked at it under a microscope, you'd probably see quite a few living things. But the reason it probably wouldn't be considered an ecosystem is it's not probably going to be there long enough so that nutrients cycle through it and energy flows. So that's the concept of ecosystem. Ecosystems are composed of different species. So if you're not familiar with what a species is, it's kind of a simple concept, but difficult to really discern one species from the next in practice. Basically, what is a species? It's what we would call the same kind of an organism. These are organisms that are the most closely related in terms of the categories that you can put things in. They're the most closely related. They can interbreed successfully. They usually look a lot alike, members of the same species. They share virtually identical genes. They have the same ancestry, same ancestral history. So in this particular slide, the pictures of these different leaves, actually the term oak is not a species term. That's actually not specific enough. It's too broad, actually. And you can see there are different types of oaks, there are different kinds of oaks, and you can tell just by the different leaf shapes in this case that here we're talking about one, two, three, four different species of oaks just in this one slide. So the term oak is actually a genus, that's the level of classification above species. Species are organized into populations, so the term population means a group of individuals of the same species in a given location. So in this slide we're looking at a population of elk in Yellowstone National Park. So the term population actually contains two components. First of all, the most important thing is that you're talking about individuals that are members of the same species. But the other thing about population is you're talking about members of the same species in a given location. So here we're looking at the population of elk in Yellowstone National Park, but you could be looking at the population of elk in, you know, Canada or the population of elk in, you know, Jackson Hole, Wyoming or something like that. So it is an area-specific thing as well as a species-specific thing. Populations live together in a community. So the term community refers to the living things in a given area and that is going to be made up of different species. So we could talk about the forest community and how that's composed of many different species of plants and other animal species that live in the forest. Community and ecosystem are very similar in terms of their definition. They both deal with different species occupying a given location. There's just a slight difference in terms of a study. If you're doing a community level study, you're usually just looking at the living things. Whereas when you're studying an ecosystem, you're also considering the abiotic components and how those influence the living things. Okay, so one of the most important things, so now we're going to pretty much focus on ecosystems for the next few weeks. One of the most important things to look at when you want to try to understand how an ecosystem functions and how it's structured is how energy flows through that ecosystem. Energy flows in a one-way path through an ecosystem. So I want you to think about if it's a one-way path, where does it start? What's the ultimate source of the energy? And where does the energy end up? So, and that is represented by what we call trophic levels. And these are just feeding levels. So these represent energy flow. Okay. Now it starts with producers. In other words, producers are where energy enters the ecosystem and producers are autotrophs. They are self feeders. Autotroph means self feeders. They make their own food. Now, how do you think they do that? Look at the picture of producers. How do these things make their own food? These are the photosynthesizers. They photosynthesize. So if that's the case, producers are the organisms by which energy enters the ecosystem. What is the ultimate source of energy to most ecosystems? It's the sun. And producers are the only ones that can convert that sunlight into and use that to build food molecules, which is what photosynthesis is. So this is how energy enters the system. Now. Since producers can use sunlight to power the process of building food molecules, they themselves, their bodies now are organic tissues, right? Organic matter. They themselves are food sources that can be consumed. So the other... trophic levels are actually all consumers. They have to eat something to get energy, right? But there are different levels of consumers. So the next trophic level up, in other words, where does the energy go after it's made into food molecules in the producers? It goes to the consumers that eat producers, which are what we call primary consumers, otherwise known as herbivores. They eat plants or photosynthesizers. Remember that not all photosynthesizers are plants, right? Think about what are the producers in an aquatic system? Well, there are plants in aquatic systems, but there are also non-plant producers in aquatic systems. Like think about phytoplankton or different types of algae. So they're not always plants. But yeah, so primary consumers are those that eat photosynthesizers. So we have an example here of grazing animals like deer. Or think about all our domestic grazers like cows and sheep and goats. They're all herbivores. Another huge category of herbivores are insects. That's what makes them pests on our plant crops because they are herbivores and eat plants. What are some other examples of primary consumers that you could think about? Think of maybe examples of primary consumers in an aquatic system. What would those be? Well, they would be anything that eats algae or phytoplankton. right? So zooplankton is a type of plankton that eats phytoplankton. So that would be an example of a primary consumer in an aquatic system. Or things like waterfowl, ducks, and geese, they eat aquatic plants. So they would be herbivores or primary consumers. The next level up is, in other words, where does the energy go that's now in the bodies of the primary consumers? it goes to whatever eats the primary consumers, which is the secondary consumers. So secondary consumers we call carnivores. They are meat eaters, right? But they specifically eat, or at least mainly eat, primary consumers. So they don't eat any meat. They eat primary consumers. They eat herbivores. So a perfect example of a secondary consumer would be wolves, which generally feed on grazing animals like, you know, antelope or gazelle, or in this case, bison. In an aquatic system, the secondary consumers would be fish that eat other fish that eat phytoplankton, right? So fish that eat the algae eaters would be secondary consumers. The next level up is what we call tertiary consumers. These are also carnivores, but they specifically eat or focus most of their feeding on secondary consumers. So an example would be a grizzly bear. that feeds on salmon and salmon feeds on other fish. So they would be a tertiary consumer or a blue heron, which, you know, eats at the tertiary level. And you can actually get higher levels than this. You can get quaternary and even above in some situations. Now, there are some categories that kind of don't fit into the chain specifically like that. And one example would be omnivores, which equally eat. plants and animals. So a black bear is an omnivore. It will eat plants and berries and things, but it will also eat small animals kind of equally. Other, like the hyena, raccoons, they equally eat both plants and animals. And then we have the detritivores. Detritivores are organisms that eat dead organic matter. And a specific category of detritivores is a decomposer. So most detritivores, if you go outside and I said, go outside and find me a detritivore, where would you look for them? Where would you look for a detritivore if I asked you to go outside and find one? You'd probably go and look in the soil, right? Because that's where a lot of the dead stuff is. It's in the soil. So that's where a lot of the detritivores feed and live is in the soil. But. Decomposers are a specific type of detritivore that are usually microscopic. They're oftentimes, you know, some type of fungus or bacteria, and they break down organic matter into its molecular components. They really break it down a lot farther than detritivores would. So an example of a detritivore might be like an earthworm that eats decaying leaf matter and then kind of poops out smaller. bits of the leaves. So they do consume dead organic matter and they do break it down farther, but a decomposer is going to break it down into its molecular components. And all of these things tend to be found in the soil, whether it's in the soil of a terrestrial system or in the sediment. at the bottom of an aquatic system. So like I said, the trophic levels represent the flow of energy in an ecosystem, starting with the sun, but most of us can't use the sun to power any of our metabolic processes, right? So we rely on the photosynthesizers who can use the power of the sun to build food molecules, which then they store in their own bodies, and now the bodies of the producers are food to us. and the rest of life, right? The rest of consumers. So, you know, the way energy is passed is through consumption for the most part after you get past photosynthesis. And so you can represent this graphically with a food web. And a food web is made up of these different chains that represent one group of organisms eating another group of organism. So in a food web, the arrows point to the direction of energy flow, starting with the sun, then going to the producers. And then where does the energy go after it gets stored in the bodies of the phytoplankton? It goes into the bodies of the zooplankton when they eat the phytoplankton, right? So those arrows represent the flow of energy. Now take a look at this picture of this food web. We know what the ultimate source of energy is in this ecosystem. It's the sun, right? But where does the energy end up? Where do those arrows end up pointing to? As you can see in this picture, it ends up in the upper level consumers, right? But it actually ends up leaving the ecosystem. Ultimately ends up leaving the ecosystem as heat, okay? Every time energy is transformed or passed along, some is lost as heat, right? And so ultimately ends up leaving the ecosystem as heat that just that just diffuses out to the atmosphere. So the source of energy to an ecosystem is the sun. The energy flows in a one-way path as it's passed through the trophic levels, through the food web, and it ends up going back into the atmosphere as heat. So it doesn't cycle in an ecosystem because we started with the sun and we end up as heat. It ends up being lost. Okay, so finally, you know, we've been talking about energy all this time. Well, let's define what do I mean when I talk about energy? Energy is usually defined as the ability to do work, which is a nice simple definition. I like that definition because it's pretty simple to understand. It can get pretty complicated though, because then you kind of have to do, you have to define what do we mean by work? And work can mean a lot of different things. So if we think about it in biological terms, work can be making a chemical bond. or breaking a chemical bond. Work can be heating up something. Work can be, of course, moving an object or something like that. So, you know, it's a simple concept. Energy is the ability to do work, but work can mean a lot of different things, especially when you think about it in a biological concept. Okay, so there are two different types of energy, right? There is Kinetic energy, which is the energy of motion. And what's the other type of energy? Potential. Potential energy is stored energy. So in this picture, you know, a perfect example of stored energy or potential energy is the energy that is stored in the roller coaster car when you're at the top of that first terrifying hill and you're sitting there waiting. for what's going to happen next, right? And there's a lot of potential energy in that roller coaster car. And you know that within five seconds, you're going to know that because that potential, that stored energy is going to be converted into kinetic energy, right? When you go flying down the hill. So the roller coaster car at the top of the hill, because of the forces of gravity, it has a lot of stored energy. And that energy can be converted into kinetic energy when that roller coaster car goes over the hill and you know that there's a lot of stored energy as you're flying down that hill there are lots of different forms of energy as well we've got light energy heat energy and heat energy actually is the lowest form of energy you know even even a campfire is a good example of you know if you've ever sat around a campfire you kind of maybe understand how heat is the lowest form of energy because unless it's really intense It can't do a lot of work, right? I mean, even if you're roasting your marshmallow, if you really want it to cook a lot, you got to stick it right in the flames, right? If you're really trying to warm yourself by a fire, you have to get real close to it. If you get a few feet back already, you know, it can't do a lot of work. It can't really warm you up that much. So heat is the lowest form of energy. We also have mechanical energy, the energy of moving things, right? We have, what's this type of energy or this form of energy? This is nuclear energy, which is actually the, comes from splitting apart atoms. We'll talk about that later in the semester. And what's this? The energy in a hamburger. Why is a hamburger energetic for us? This is what we call chemical energy. The energy in the hamburger is in the chemical bonds. and our bodies have to break those bonds in order to access that energy. We do that through cellular respiration. There are different levels of energy quality. High quality energy is associated with high temperatures. It can do a lot of work. Okay, it's very concentrated. Can you think of some examples of high quality energy? Well here think about what fuels, what type of fuel underlies all major economies in the world. Those are the fossil fuels, right? I'll talk about sunlight in a second. Coal, oil, natural gas, those are the three fossil fuels. The use of these underlies all major economies. This is what we use to power our factories and things. So why do we do that? Because they represent very high quality examples of energy because they are very concentrated. When you burn these fuels, it releases a lot of heat that can be used to do a lot of work. There are some problems with using these fuels. They're very polluting. We'll talk a lot about that. But there's a reason why we use them so much, and that's because they do produce a lot of heat. They can do a lot of work. Now, sunlight is kind of tricky. Diffuse sunlight, like when you walk outside, just the sun shining down, is actually not a very high quality source of energy. It can warm us up. You know, it can burn your skin if you're really fair-skinned. Can't really do a lot of work, though. In order to use sunlight, it can be a high-quality source of energy, but we have to focus the beam, okay? And so solar energy, all the technology around solar, for the most part, involves focusing the beam of sunlight into one particular location, and that's what makes it high-quality. There are also low-quality forms of energy, and like I said before, the lowest-quality energy is dispersed heat. So the reason I have a picture of the ocean here is because oceans actually contain a lot of heat. Think of all the chemical reactions happening in an ocean at any given moment of time. You know, and with every chemical reaction, heat is released and that can be absorbed by the ocean water. But it's so dispersed. It's such a huge body of water that it's not really, it can't do a lot of work. We really can't capture that heat and do anything with it. It's too dispersed and diffuse. It's not associated with really high temperatures. So that's a low quality form of energy. It's kind of frustrating. I read a statistic that said all the energy contained in the Atlantic Ocean in terms of heat, the heat energy is equivalent to all the oil, the energy stored in all the oil in the Middle East. So there's a lot of energy heat energy in the Atlantic Ocean but we can't use it it's too diffuse.

And the biosphere is basically defined as the region of Earth occupied by life. And it's composed of three different spheres. The atmosphere is the zone of air that surrounds earth that supports and contains life. The lithosphere is the zone, the terrestrial zone.

It's made up of the earth's crust and of course that supports and contains life. And then we have the hydrosphere which is the zone of water on earth that supports and contains life. The biosphere is made up of non-living components. We call those abiotic components.

A means non, and of course, bio means life. So these are the non-living components of the biosphere that, of course, very much so influence and affect the living components. So there's some examples of abiotic components here on the slide. Fire, the presence of fire, of course, could greatly affect life on Earth. Climate things like precipitation and temperature greatly affect life on Earth.

Topography, which is the slope of the landscape. Soil type. Try to think of some other abiotic components of the biosphere that affect life on Earth. Things like maybe the amount of sunlight available, maybe the amount of wind, seasonality. All of these things are abiotic components of the biosphere that greatly influence.

what species occur where, and how well different species do on Earth. Then of course there are the biotic components or the living components or what I like to call the critters that make up the biosphere. We'll spend a lot of time talking about these and the different things that influence their success and reproduction on Earth. When you study the natural world, the first thing you have to ask yourself is of what scale of study am I going to look at the natural world?

For example, am I interested in biosphere level questions? For example, how is the climate changing on earth and how is that influencing life on earth? That would be a biosphere level question.

Or are you interested in a particular location and how species are interacting with their environments in that one location? Are you interested in just one particular species? in a particular spot and you just want to ask questions about it. So you have to determine what level of scale or what category of organisms you're going to look at. And in this class, the level of scale that we're going to be most concerned with is the ecosystem level.

So an ecosystem is defined as a group of different species in a given area. So we're not just looking at one species here, we're looking at a group of different species in a given area. And when you do an ecosystem study, you're looking at not only interactions between the living things, but interactions between the living things and their environment. So there is that abiotic component to ecosystem studies. So this part about an ecosystem is defined as being stable enough so that nutrients, cycle and energy flows.

You might not know what that quite means yet. We are going to talk about both those things, nutrients, cycling, and energy flowing, but just realize at this point that an ecosystem is a system that's going to be around for a while. It's not just there for a few minutes. There is some sustainability to it. For example, a puddle in a middle of a parking lot probably wouldn't be considered an ecosystem.

Now, would it not be because... Consider it an ecosystem because there's no life in it, because there's no species living in that puddle? No, there's probably a lot of things living in that puddle, even if it's there for just a few minutes.

If you took a sample of the water and looked at it under a microscope, you'd probably see quite a few living things. But the reason it probably wouldn't be considered an ecosystem is it's not probably going to be there long enough so that nutrients cycle through it and energy flows. So that's the concept of ecosystem.

Ecosystems are composed of different species. So if you're not familiar with what a species is, it's kind of a simple concept, but difficult to really discern one species from the next in practice. Basically, what is a species?

It's what we would call the same kind of an organism. These are organisms that are the most closely related in terms of the categories that you can put things in. They're the most closely related. They can interbreed successfully.

They usually look a lot alike, members of the same species. They share virtually identical genes. They have the same ancestry, same ancestral history.

So in this particular slide, the pictures of these different leaves, actually the term oak is not a species term. That's actually not specific enough. It's too broad, actually.

And you can see there are different types of oaks, there are different kinds of oaks, and you can tell just by the different leaf shapes in this case that here we're talking about one, two, three, four different species of oaks just in this one slide. So the term oak is actually a genus, that's the level of classification above species. Species are organized into populations, so the term population means a group of individuals of the same species in a given location. So in this slide we're looking at a population of elk in Yellowstone National Park.

So the term population actually contains two components. First of all, the most important thing is that you're talking about individuals that are members of the same species. But the other thing about population is you're talking about members of the same species in a given location.

So here we're looking at the population of elk in Yellowstone National Park, but you could be looking at the population of elk in, you know, Canada or the population of elk in, you know, Jackson Hole, Wyoming or something like that. So it is an area-specific thing as well as a species-specific thing. Populations live together in a community.

So the term community refers to the living things in a given area and that is going to be made up of different species. So we could talk about the forest community and how that's composed of many different species of plants and other animal species that live in the forest. Community and ecosystem are very similar in terms of their definition.

They both deal with different species occupying a given location. There's just a slight difference in terms of a study. If you're doing a community level study, you're usually just looking at the living things. Whereas when you're studying an ecosystem, you're also considering the abiotic components and how those influence the living things. Okay, so one of the most important things, so now we're going to pretty much focus on ecosystems for the next few weeks.

One of the most important things to look at when you want to try to understand how an ecosystem functions and how it's structured is how energy flows through that ecosystem. Energy flows in a one-way path through an ecosystem. So I want you to think about if it's a one-way path, where does it start? What's the ultimate source of the energy?

And where does the energy end up? So, and that is represented by what we call trophic levels. And these are just feeding levels. So these represent energy flow.

Okay. Now it starts with producers. In other words, producers are where energy enters the ecosystem and producers are autotrophs.

They are self feeders. Autotroph means self feeders. They make their own food.

Now, how do you think they do that? Look at the picture of producers. How do these things make their own food?

These are the photosynthesizers. They photosynthesize. So if that's the case, producers are the organisms by which energy enters the ecosystem.

What is the ultimate source of energy to most ecosystems? It's the sun. And producers are the only ones that can convert that sunlight into and use that to build food molecules, which is what photosynthesis is.

So this is how energy enters the system. Now. Since producers can use sunlight to power the process of building food molecules, they themselves, their bodies now are organic tissues, right? Organic matter. They themselves are food sources that can be consumed.

So the other... trophic levels are actually all consumers. They have to eat something to get energy, right?

But there are different levels of consumers. So the next trophic level up, in other words, where does the energy go after it's made into food molecules in the producers? It goes to the consumers that eat producers, which are what we call primary consumers, otherwise known as herbivores.

They eat plants or photosynthesizers. Remember that not all photosynthesizers are plants, right? Think about what are the producers in an aquatic system?

Well, there are plants in aquatic systems, but there are also non-plant producers in aquatic systems. Like think about phytoplankton or different types of algae. So they're not always plants. But yeah, so primary consumers are those that eat photosynthesizers.

So we have an example here of grazing animals like deer. Or think about all our domestic grazers like cows and sheep and goats. They're all herbivores.

Another huge category of herbivores are insects. That's what makes them pests on our plant crops because they are herbivores and eat plants. What are some other examples of primary consumers that you could think about?

Think of maybe examples of primary consumers in an aquatic system. What would those be? Well, they would be anything that eats algae or phytoplankton. right?

So zooplankton is a type of plankton that eats phytoplankton. So that would be an example of a primary consumer in an aquatic system. Or things like waterfowl, ducks, and geese, they eat aquatic plants.

So they would be herbivores or primary consumers. The next level up is, in other words, where does the energy go that's now in the bodies of the primary consumers? it goes to whatever eats the primary consumers, which is the secondary consumers. So secondary consumers we call carnivores.

They are meat eaters, right? But they specifically eat, or at least mainly eat, primary consumers. So they don't eat any meat. They eat primary consumers.

They eat herbivores. So a perfect example of a secondary consumer would be wolves, which generally feed on grazing animals like, you know, antelope or gazelle, or in this case, bison. In an aquatic system, the secondary consumers would be fish that eat other fish that eat phytoplankton, right? So fish that eat the algae eaters would be secondary consumers. The next level up is what we call tertiary consumers.

These are also carnivores, but they specifically eat or focus most of their feeding on secondary consumers. So an example would be a grizzly bear. that feeds on salmon and salmon feeds on other fish.

So they would be a tertiary consumer or a blue heron, which, you know, eats at the tertiary level. And you can actually get higher levels than this. You can get quaternary and even above in some situations.

Now, there are some categories that kind of don't fit into the chain specifically like that. And one example would be omnivores, which equally eat. plants and animals.

So a black bear is an omnivore. It will eat plants and berries and things, but it will also eat small animals kind of equally. Other, like the hyena, raccoons, they equally eat both plants and animals. And then we have the detritivores.

Detritivores are organisms that eat dead organic matter. And a specific category of detritivores is a decomposer. So most detritivores, if you go outside and I said, go outside and find me a detritivore, where would you look for them?

Where would you look for a detritivore if I asked you to go outside and find one? You'd probably go and look in the soil, right? Because that's where a lot of the dead stuff is. It's in the soil.

So that's where a lot of the detritivores feed and live is in the soil. But. Decomposers are a specific type of detritivore that are usually microscopic.

They're oftentimes, you know, some type of fungus or bacteria, and they break down organic matter into its molecular components. They really break it down a lot farther than detritivores would. So an example of a detritivore might be like an earthworm that eats decaying leaf matter and then kind of poops out smaller.

bits of the leaves. So they do consume dead organic matter and they do break it down farther, but a decomposer is going to break it down into its molecular components. And all of these things tend to be found in the soil, whether it's in the soil of a terrestrial system or in the sediment.

at the bottom of an aquatic system. So like I said, the trophic levels represent the flow of energy in an ecosystem, starting with the sun, but most of us can't use the sun to power any of our metabolic processes, right? So we rely on the photosynthesizers who can use the power of the sun to build food molecules, which then they store in their own bodies, and now the bodies of the producers are food to us.

and the rest of life, right? The rest of consumers. So, you know, the way energy is passed is through consumption for the most part after you get past photosynthesis.

And so you can represent this graphically with a food web. And a food web is made up of these different chains that represent one group of organisms eating another group of organism. So in a food web, the arrows point to the direction of energy flow, starting with the sun, then going to the producers. And then where does the energy go after it gets stored in the bodies of the phytoplankton? It goes into the bodies of the zooplankton when they eat the phytoplankton, right?

So those arrows represent the flow of energy. Now take a look at this picture of this food web. We know what the ultimate source of energy is in this ecosystem.

It's the sun, right? But where does the energy end up? Where do those arrows end up pointing to?

As you can see in this picture, it ends up in the upper level consumers, right? But it actually ends up leaving the ecosystem. Ultimately ends up leaving the ecosystem as heat, okay?

Every time energy is transformed or passed along, some is lost as heat, right? And so ultimately ends up leaving the ecosystem as heat that just that just diffuses out to the atmosphere. So the source of energy to an ecosystem is the sun. The energy flows in a one-way path as it's passed through the trophic levels, through the food web, and it ends up going back into the atmosphere as heat.

So it doesn't cycle in an ecosystem because we started with the sun and we end up as heat. It ends up being lost. Okay, so finally, you know, we've been talking about energy all this time. Well, let's define what do I mean when I talk about energy?

Energy is usually defined as the ability to do work, which is a nice simple definition. I like that definition because it's pretty simple to understand. It can get pretty complicated though, because then you kind of have to do, you have to define what do we mean by work? And work can mean a lot of different things.

So if we think about it in biological terms, work can be making a chemical bond. or breaking a chemical bond. Work can be heating up something. Work can be, of course, moving an object or something like that. So, you know, it's a simple concept.

Energy is the ability to do work, but work can mean a lot of different things, especially when you think about it in a biological concept. Okay, so there are two different types of energy, right? There is Kinetic energy, which is the energy of motion.

And what's the other type of energy? Potential. Potential energy is stored energy. So in this picture, you know, a perfect example of stored energy or potential energy is the energy that is stored in the roller coaster car when you're at the top of that first terrifying hill and you're sitting there waiting.

for what's going to happen next, right? And there's a lot of potential energy in that roller coaster car. And you know that within five seconds, you're going to know that because that potential, that stored energy is going to be converted into kinetic energy, right?

When you go flying down the hill. So the roller coaster car at the top of the hill, because of the forces of gravity, it has a lot of stored energy. And that energy can be converted into kinetic energy when that roller coaster car goes over the hill and you know that there's a lot of stored energy as you're flying down that hill there are lots of different forms of energy as well we've got light energy heat energy and heat energy actually is the lowest form of energy you know even even a campfire is a good example of you know if you've ever sat around a campfire you kind of maybe understand how heat is the lowest form of energy because unless it's really intense It can't do a lot of work, right? I mean, even if you're roasting your marshmallow, if you really want it to cook a lot, you got to stick it right in the flames, right? If you're really trying to warm yourself by a fire, you have to get real close to it.

If you get a few feet back already, you know, it can't do a lot of work. It can't really warm you up that much. So heat is the lowest form of energy.

We also have mechanical energy, the energy of moving things, right? We have, what's this type of energy or this form of energy? This is nuclear energy, which is actually the, comes from splitting apart atoms. We'll talk about that later in the semester. And what's this?

The energy in a hamburger. Why is a hamburger energetic for us? This is what we call chemical energy. The energy in the hamburger is in the chemical bonds. and our bodies have to break those bonds in order to access that energy.

We do that through cellular respiration. There are different levels of energy quality. High quality energy is associated with high temperatures.

It can do a lot of work. Okay, it's very concentrated. Can you think of some examples of high quality energy?

Well here think about what fuels, what type of fuel underlies all major economies in the world. Those are the fossil fuels, right? I'll talk about sunlight in a second. Coal, oil, natural gas, those are the three fossil fuels. The use of these underlies all major economies.

This is what we use to power our factories and things. So why do we do that? Because they represent very high quality examples of energy because they are very concentrated.

When you burn these fuels, it releases a lot of heat that can be used to do a lot of work. There are some problems with using these fuels. They're very polluting. We'll talk a lot about that. But there's a reason why we use them so much, and that's because they do produce a lot of heat.

They can do a lot of work. Now, sunlight is kind of tricky. Diffuse sunlight, like when you walk outside, just the sun shining down, is actually not a very high quality source of energy.

It can warm us up. You know, it can burn your skin if you're really fair-skinned. Can't really do a lot of work, though. In order to use sunlight, it can be a high-quality source of energy, but we have to focus the beam, okay? And so solar energy, all the technology around solar, for the most part, involves focusing the beam of sunlight into one particular location, and that's what makes it high-quality.

There are also low-quality forms of energy, and like I said before, the lowest-quality energy is dispersed heat. So the reason I have a picture of the ocean here is because oceans actually contain a lot of heat. Think of all the chemical reactions happening in an ocean at any given moment of time. You know, and with every chemical reaction, heat is released and that can be absorbed by the ocean water. But it's so dispersed.

It's such a huge body of water that it's not really, it can't do a lot of work. We really can't capture that heat and do anything with it. It's too dispersed and diffuse.

It's not associated with really high temperatures. So that's a low quality form of energy. It's kind of frustrating. I read a statistic that said all the energy contained in the Atlantic Ocean in terms of heat, the heat energy is equivalent to all the oil, the energy stored in all the oil in the Middle East.

So there's a lot of energy heat energy in the Atlantic Ocean but we can't use it it's too diffuse.

Transcript for:Exploring Natural World and Ecosystems

Transcript for:
Exploring Natural World and Ecosystems