Hi. In this video, we'll be taking a look at ecology, which is the study of organisms' interactions with one another and their environment. Now just as the living world can be broken down into various layers of a hierarchy, the field of ecology can also be subdivided based on these different hierarchies. So, for example, the organism is, sort of, the fundamental unit of the living world. Atoms are to a chemist as organisms are to an ecologist, in a sense. Now, the organism is just an individual living system, and so an organismal ecologist is going to be interested in studying that individual living system, and so they're gonna wanna look at things like physical adaptations of an organism. For example, you know, traits that increase an organism's ability to gather or obtain food, something like that. Now populations are groups of organisms of the same species that live in the same area, and it's worth noting that it's possible to have, multiple populations of 1 species in the same area, and that's actually a concept we'll visit later. Now population ecologists are going to want to look at things like the abundance and distribution of organisms in a population. So for example, you know, how many members of the population are there? Something as seemingly simple as that is an interesting question. And especially the population ecologists are going to want to look at changes in this stuff over time. So are the populations increasing? Are they decreasing? Are populations merging together? Are, populations splitting into different populations? That sort of stuff. Now community is a group of populations that cohabit the same area. Now these are populations of different species, but basically it's the, sum of all the different populations of species in a particular area. And community ecologists are going to want to look at the interactions between species, And don't let the, seemingly positive, term community fool you. Oftentimes this is gonna be one organism eating another organism. Now, the ecosystem is basically the community plus the physical environment, so the community is just the populations, just the organisms. The ecosystem adds the physical terrain that those organisms live in. And, ecosystem ecologists are gonna wanna look at things like the flow of nutrients and energy through ecosystems and through organisms. So looking at our images here you can see, here we have a single organism, it's just a frog. Right? And here this is actually a graph of the human population. And hopefully, you can see that we are looking at 1,000,000,000 on the side here, and we are very close, to that 8000000000 mark at present. And, hopefully this chart astounds you, as the rate of human population growth has been just, you know, unbelievable in the past century. I mean, we went from having less than 2,000,000,000 humans on earth ever to now almost 8,000,000,000 in under a 100 years. Pretty mind boggling stuff. Now here we can see both a community and an ecosystem. Let me actually jump out of the way. Now, in terms of the community you have these fish, you have a a nice little starfish there, coral all around. Those are gonna all make up the community. Now, the ecosystem here is also going to include things like the rock and the water that's all around these organisms. So, you know, community, I just, you know, always think of it as basically ecosystem minus all the terrain and stuff. Now landscapes are an idea, it's essentially, interconnected ecosystems, sort of like a hierarchical layer above ecosystems. And it's helpful because, you know, ecosystems aren't just discrete units. You know, there's not a border on, you know, like a a national border, I mean, on an ecosystem, you know, they touch each other, there's sort of transitional zones between them. And so landscapes sort of, take a look at, you know, the greater picture of how ecosystems interact, and also, you know, how energy and materials are going to be exchanged across ecosystems. Now when you get all the ecosystems that exist together, what you have is the biosphere, earth. And global ecology is going to be, again, just, you know, the study of the biosphere. It's everything, really. Often though, they're going to be looking at the human impact on the biosphere. So they're gonna be interested in things like, for example, climate change, which we'll be talking about at length. Now conservation biology is essentially the effort to counteract a lot of this stuff. It's the effort to preserve and manage earth's biodiversity, and we'll be talking more about that later. Now, related to ecology is the study of biogeography, which is essentially, the study of the distribution and species, sorry, distribution of species and ecosystems over geologic history. So this is going to be, for example, studying things like, you know, why there are certain organisms on some continents and not others, you know. For example, here, you know, we're looking at the, sort of supercontinent that used to exist on earth, But, you know, of course due to tectonic activity, you know, the continents broke apart, they went their own directions, and some, types of organisms got isolated to particular continents. So, you know, these are all just ideas that biogeography is going to explore. That's that's sort of the, interest that those scientists would have. So with that, let's turn the page.
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Biotic and Abiotic Factors
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When we look at ecosystems, we're gonna wanna examine the biotic factors and abiotic factors. Now the biotic factors are the living components. This not only includes the organisms, but actually the interactions between organisms as well. Now the non living parts of the environment, or the abiotic factors, are going to include things like temperature, moisture, oxygen, and sunlight. You can see a bunch of those in this image here, just highlighted. Now, abiotic factors are gonna have quite an influence on an organism's distribution and behaviors. They're going to limit where the organism can survive, and also, in part determine what the organism has to do to survive. Now, it's going to be the interplay between biotic and abiotic factors that determine the distribution of a species, and you can see a nice map of the distribution of a species here. We're actually looking at the distribution of the common juniper, it's a little conifer plant. It's where juniper berries come from, if you've ever heard of those. Now, geologic activity or geologic changes, I should say, will have a huge impact on the distribution of species. I mean, you know, we just mentioned how the movement of the continents has played a huge role in in determining the history of life on the various continents on Earth. Other factors will also play a role in the distribution of species, like dispersal, which is the movement from the location of birth to breeding site. You know, for some organisms, this isn't gonna be very far. However, there are some organisms that migrate huge distances to get to their breeding sites, and, you know, they can be separated by oceans or, you know, vast stretches of land, mountains. So the, you know, geologic factors involved are going to play a big role in this. Now range is the actual geographic distribution of a species. And, for example, you know, we just saw the range of the juniper up there. However, the, you know, the range of an organism can is not necessarily confined to one continent is is the point I want to make. Now the Wallace line is an interesting biogeographical division between Asia and Australia that kind of illustrates this point nicely about, how organisms are going to be limited, maybe not the right word, affected, maybe a better word, by geologic changes. So let me jump out of the way here. Hopefully, you look at this map and and you recognize that we are looking at Southeast Asia, and here's Australia, and, you know, all these islands in here. We have, you know, in the well, parts of Indonesia. You know, this isn't a geography lesson. So the point I wanna make about the Wallace line is that during, during the last ice age, there essentially, a lot of, water was frozen, so the ocean levels were reduced. And as a result, land masses looked a little different. Now here you can actually see what the landmasses, in theory would have looked like by these sort of beige outlines. So, you know, highlighted darker, like around in here, those are the actual continent lines today with our current ocean levels, our current sea levels. However, you can see that when the ocean levels were lower there was more land area. Now, the point about this Wallace line is that it's a division between Asia and Australia, and you can see there's other lines in here. Know, I don't I don't want you to worry about that. We're just gonna look at this Wallace line that kind of goes along here. And he he's basically, or sorry, this line, which is named after this guy Wallace, the idea is basically that this division existed between these two land masses that prevented a spread of species between them. Right? You're not gonna find species that are, you know, both somewhere in here and also somewhere in here. And, you know, you're not gonna find ancestors of species over here, for example, over in this area. And that's because there was this barrier that separated them. And, you know, even though the land masses, were shaped differently, there was still this, actual, you know, water division between them that, you know, separated the diversity of life between these land masses. In case you're curious, that water division existed because there's actually a very deep trench in the ocean there that, ensured there was still going to be a water barrier between those two landmasses. Now exotic species are gonna be non native species to an area, and sometimes these exotic species will actually, do really well in this new environment and they'll spread and then they'll actually compete with the local flora and fauna. And they can actually have disastrous effects on ecosystems. Here, this looks like a harmless little organism. It's called a zebra mussel. This organism is just wreaking havoc in, the Great Lakes in America and really in, you know, freshwater all across the country. You know, these organisms are super invasive, and they totally change ecosystems, because they basically, they end up eating a lot of their filter feeders, they end up eating a lot of stuff out of the water, which allows for more light to get in, and that causes, you know, much greater blooms of algae, for example. So, you know, the point is they have a major effect on the ecosystems and they throw them out of balance. And so invasive species are usually a bad thing. You don't want invasive species. Exotic species, on the other hand, that just means that they're not from the area. So just want to sort of point out that the invasive has more negative connotation. Exotic, not necessarily a negative thing. However, exotic species can become invasive. Now, with that, let's go ahead and turn the page.
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Weather and Climate
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When we talk about weather, we're talking about the short term atmospheric conditions in an area. These are gonna be things like rainfall or what temperature it is outside. Now climate is really looking at long term weather patterns of an area. So with weather, we're wondering if it's raining outside, but with climate, we're wondering how many inches of rain did we receive here in the past year? Something like that. Now climate can actually be viewed, from 2 different lenses. You can look at macroclimate, which is climate on the global, regional, and landscape scale. And you can also look at microclimate, which is climate of a small area, and this can be really small. I mean, we could be talking about a puddle. And the thing about microclimates is they usually have a climate that differs from the surrounding macroclimates, so they kind of stand out for that reason. Now climographs are just representations of climate data. And we actually have a climate graph right here. This is from NASA, and it's showing global temperature averages for the year 2015. Now everything that is in color on this image, as in all the areas that aren't white, are different from the average. And hopefully, you can see that the earth was quite a lot warmer than normal in 2015, and this is pretty alarming, you know. This is this is, an aberration in average temperatures, and it's actually part of a trend that has been ongoing, the global temperature averages increasing. Now, atmospheric conditions can lead to some pretty amazing phenomena. You know, we tend to think about physical processes like, you know, things moving to diff due to differences in temperature, for example, on a small scale. But this kind of stuff is happening on a large scale across the planet at all times. So I want to talk about this, particular type of atmospheric circulation called Hadley cell, that happens right around the equator. Now, the Hadley cell is kind of, if we're looking at the surface of the earth here, and our atmosphere sits on top. The Hadley cell circulates air, not only up and down latitude on the globe, but also, up and down through the atmosphere. So the air in the Hadley cell is circulating north south, but it's also circulating vertically, you know, it's moving up and down through the atmosphere as well. So hopefully you can, gather that from this image. These red arrows are trying to represent the movement of air in Hadley cell. And basically what's gonna happen is at the equator we get the strongest sunlight. So the air there is going to be hot, and it's gonna be hotter than the air that's further away from the equator. Hopefully, you've followed me so far. Now this warm air allows it, or this warmth in the air allows that air to hold more moisture. And hot things rise up. Right? So this air is gonna rise up in the atmosphere. So basically around the equator we get this hot warm air, and it rises up in the atmosphere. Now as it rises, as this air rises, it's gonna cool. And as it cools, it's going to lose moisture as precipitation. So as this hot moist air rises up it's going to cause rainfall. Right? It's going to lose the moisture it's holding. Now this cooling air, not only so the the air is rising up in the atmosphere as it cools, but as the air cools it also gets pushed toward the poles. Right? So it's going to go up, and then also start to move either North or South. I'm showing an example going North could just as easily be working in this band down here, showing the opposite direction, like you can see here. However, I'm just gonna keep working, in this, northern particular band. Now the cold air, as it's moving towards the pole, it will start to sink. Right? Cold things sink, hot things rise up, thermodynamics. So as it moves towards the pole it's going to sink down in the atmosphere. So hopefully you can see how these arrows are showing the movement of that air. Right? The hot air rises up, cools, moves towards the poles. Once it gets around this, you know, mid latitude here, around 30 degrees, and again, this either be north or south, you'll have them in both both areas. You know, right when it gets around there it's gonna get cold enough that it's gonna sink back down. Now what's so cool about the Hadley cell is something we can literally see right here on this map. Notice how in, the continent of Africa there's almost like a line right here. It's actually called the Sahel band, in case you're curious. And, basically, it's going to separate this jungle y area, right, this green area from the desert up here. Now why is there such a stark division there? The answer is in part because of Hadley cells. Because the rainfall distribution is much higher around the equator and it's quite low in the peripheral areas. So these areas around the equator get all the rainfall. And look, this area of desert exists right in essentially the part where the Hadley cell has, or rather the air moving, has, given off all its moisture. It's gonna be dry. Right? And it's gonna be dry air that's moving over this area, this desert. So the point being that these atmospheric circulations, and there's more than just the Hadley cell, this is just one to illustrate a point, you know, there's more than just this. But these atmospheric circulations have major impact on the ecosystems of our planet, and, you know, you can't really make it any more apparent than right here, this line through the continent. So with that, let's go ahead and flip the page.
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Earth's Angle and Sunlight
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11m
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The equator receives more sunlight than anywhere else on Earth, and this is why it's the warmest part of our planet. Now to understand why, we need to look at how the sun's rays hit the Earth. But for our purposes right now, I want you to pretend that the equator is just this red line I'm drawing through the planet. We'll, in a moment, get to why the image has the Earth tilted and and what's important about that. But for now, I want you to pretend that the equator is just, level with the lines of the sun's rays. So the sun's rays that hit the Earth more or less straight on, they're coming in more or less perpendicular to the Earth's surface, those rays are going to spread their energy over a smaller area than, for example, these rays up here that come in at an angle to the Earth's surface. Right? We sort of have an angle there. Because of that angle, these rays up top are going to spread out over a larger area, whereas these rays by the equator are gonna be concentrated in a smaller area. So let's just assume it's the same amount of energy in both regions. You have the same amount of energy in a smaller area versus the same amount of energy in a larger area. Well, in the larger area, you're gonna have to spread your energy thinner. Right? That means you're gonna have less energy per area, so so it's gonna be colder. That's why it's colder up at the poles and warmer at the equator. It's due to how the energy from the sunlight is being spread out, and that's due to the angle at which these rays are hitting the Earth. Now, let's get to the tilt of the Earth in this image. So, the Earth experiences seasons, you know, and we refer to them as, you know, spring, summer, winter, or fall, winter. Really, what we're talking about though is the tilt of the Earth's axis. So this line is what we know as the Earth's axis. It's the axis around which the Earth spins on a daily basis. Right? So here in this image of the Earth revolving around the sun, you can see these little purple circular arrows. Those are showing the Earth spinning around its axis. Now, this axis actually this axis, the position of this axis relative to the sun changes. So sometimes, like we see in our image, the axis is pointed away from the sun. Whereas, other times, that axis is actually gonna be pointed towards the sun. Now, when the axis is pointed away from the Sun, we can see that this upper half of the Earth, which we call the Northern Hemisphere, that northern hemisphere is basically leaning away from the Sun. And notice that, you know, assuming that the rays in this image are, you know, all the rays coming off the Sun, obviously, it's a gross oversimplification, but notice how it's only getting 2 sun rays and the southern hemisphere is getting all the rest. Well, when the northern hemisphere is pointed away from the sun like that, that's what we call winter. Right? That's when the Northern Hemisphere is colder because it's getting even less sunlight than usual. Now, when the Northern Hemisphere points towards the sun, notice that now it's gonna be getting more sun rays than the southern hemisphere. That's what we call summer. So the Earth's axis is changing position relative to the Sun as it moves around the Sun, and that's what we experience as seasons. And, hopefully, this little drawing here made it clear that the Northern Hemisphere and the Southern Hemisphere are actually on opposite seasonal schedules, so to speak. You know, we just refer to, our northern hemisphere's cold months as winter, but that's actually gonna be the hottest time of the year for the southern hemisphere. And likewise, when it's warmest in the Northern Hemisphere, it's gonna be colder in the Southern Hemisphere. So, you know, these, terms for fall or I'm sorry, for seasons, fall, winter, spring, and summer are kind of biased or towards the Northern Hemisphere. So sorry people in Australia. I'm thinking about you. Now, in addition to the atmosphere circulating, the oceans will also circulate, and this will affect climate patterns, especially those of coastal regions. Now the oceans circulate all over the planet and we'll talk about, that sort of big picture just a second. But before that, I wanna talk a little bit about how coastal regions are affected. To understand that, you need to understand this property of water that we know is specific heat, which is basically the ability of a substance to absorb energy, without changing its own temperature. So, what does that mean? If you have a high specific heat, you can absorb a lot of energy and your temperature will only go up a little bit. If you have a low specific heat, your temperature will go up a lot when you absorb, you know, just a little bit of energy. This is a bit of an oversimplification, but for our purposes, that's all you need to understand. So water has a high specific heat. It can absorb large amounts of energy, and it can also store those large amounts of energy. So around coastal regions, oceans are actually, going to be able to warm and cool their coastal areas depending on the relative temperatures of the air air in the water. So I'm gonna give you an example of this, and we're gonna get into some details. You don't really need to understand all the details here. I just wanna explain how this is happening. So you can see how these natural forces work together to produce, well, frankly, phenomena that we're pretty familiar with, that we experience on a regular basis. So so what happens, during the day in a coastal area? Well, during the day, there's the sun out and what's gonna happen is the ocean or the water, I should say, is gonna absorb more, heat than the land, and that's being represented by these red arrows. So that does not mean the air over the ocean or the air over the land. We're talking about the actual ocean and the actual Earth absorbing heat from the sunlight. Now, because the ocean is absorbing some or me actually say this another way. Because the land isn't absorbing as much heat as the ocean, it means the air above the land is actually going to be warmer than the air above the ocean. And that is, again, because the land is not absorbing as much energy as the ocean. The ocean is absorbing lots of energy, meaning the air above it is not absorbing or not getting all of that energy, so to speak. So what does this do? Well, if we have hot air, so let's just say, hot air, it's gonna rise up. When hot air rises, it's gonna leave behind a low pressure pocket. So let's just say low p. So the hot air rises and that leaves us with low pressure. Now, because the air is cooler over the ocean and therefore, denser, we're gonna have higher pressure over here, lower pressure over the land. So the air is gonna move off the ocean up into the land, also known as a sea breeze. Now, at night, we're basically going to have, the opposite scenario play out. The ocean absorbed more energy during the day. So, at night, when things are cooled off, it's gonna release more energy. Since it's releasing more energy, that means that the air above the ocean is gonna be hotter. So let's say, do the same thing, hot air, it's gonna rise. Now, the land didn't absorb as much energy during the day, meaning it's gonna release less heat at night, so it's not going to be, the air above the land is not gonna be as warm. It's gonna be cooler and it's going to be denser. So we're gonna have higher pressure on land Because the hot air over the ocean is gonna rise, we're gonna have lower pressure over the ocean, which means we're gonna have a breeze moving from the land out to sea. Now you really don't need to worry about memorizing all the intricacies of these processes. I'm just explaining all the steps so you can see how, you know, things as simple as energy will cause all of these, you know, patterns in climate and weather that we experience on a daily basis, or some of us do, I don't know if you live by the ocean or not, I shouldn't say that, I live by the ocean, so I experience these regularly. Now let's talk about those big picture ocean currents. Right? You know, here we're looking at at really just like a a small microcosm of what's going on. But as you can see in this image, I mean, the ocean currents are moving all over the planet, and they carry warm and cool water to various regions. Now, notice how, for example, here in the Pacific, we have a warm current that moves up along the coast of Asia here, and it's actually gonna come across the Pacific and move down the coast of California. That's why the Pacific Ocean in California despite, you know, for example, Southern California's warm temperatures, always cold, always cold. Even in the summer, it's always cold. Now, I grew up on the East Coast and we have that nice warm water that comes up the coast of, or the Eastern Coast of the United States. But notice how across the Atlantic, they actually have a cold current moving down the coast of Africa there. And you can see this pattern repeated on other, in other currents across the globe. But the point is, you know, these are not static systems. They're dynamic. They're flowing. There's energy moving through them, and that is affecting climate. So with that, let's go ahead and flip the page.
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Mountains and Air Currents
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3m
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Mountains can have a really interesting effect on climate, because they provide a physical barrier in the atmosphere, which is going to impede or at the very least have some effect on airflow. Now one of the really cool phenomena that can arise from a mountain is what's known as a rain shadow, and this is basically an area that doesn't receive a lot of moisture because it's blocked by a mountain. So what's essentially gonna happen is, as warm moist air rises over a mountain, it's going to cool and condense. And when it cools it's going to lose moisture as precipitation. And so when that air finally gets over the top of the mountain it's pretty much gonna have lost all its moisture. So as it advances and moves over to the other side of the mountain it's not going to have any moisture to provide as rain. So we are going to have what's called a rain shadow. This dry area due to a mountain blocking the movement of moist air. Now this can occur on a smaller scale like we see here, but we actually have a really amazing example on a massive scale, the Himalayas. That's what we're looking at here. This these are the Himalayan mountains, sort of on the, you could think of it as the northern edge of the Indian subcontinent, is where you'll find them on a map. And you can see there's a line, literally a line, that goes along here that represents the, essentially the boundary of our rain shadow. Right? It's all green on this side because that's the side that has the moist air. Now, when that air rises over these mountains it loses its moisture. And that's why this landscape, known as the Tibetan Plateau, is particularly dry because all that rain is being blocked. This is a rain shadow. Now, global air currents will also have a major influence on climate patterns. And you can see that, in this figure we have, what are known as the prevailing winds. These are sort of like major wind patterns, and, you know, of note are these lines in blue, which represent what are called the westerly winds, and because they blow from the West. And then we also have in yellow what are called the trade winds, which are northeasterly winds because they blow from the northeast. Now, you know, there are many other types of global air currents, for example, the jet stream, that are gonna have a major influence on, the weather patterns around in the rather the climate patterns around the Earth. It gets very complicated very quickly, and to be honest, you know, people are still sort of understanding some of the science behind it. So, really, all I want you to know about wind is just that it can have a, not only global effect, but in local terms can have a strong effect because wind will actually increase heat loss and water loss. So wind will have a strong effect on local climate and as we can see in this figure, it also will have a major effect on global climate. So with that, let's go ahead and flip the page.
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Biome and Biomass
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9m
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Okay, everyone. In this lesson, we are gonna be talking about biomes. Now what are biomes? You've probably heard this word before, but what's the exact definition? What does it mean? So a biome is gonna be basically a very, very, very, very large community of organisms and their environment. So this is going to be a distinct formation of flora and fauna. Remember, this means biotic things, living organisms. Flora means plants. Fauna means animals or other living things like bacteria or protists or anything like that. So a distinct formation of the flora and the fauna and abiotic factors. Remember, these are nonliving factors. These are gonna be things like rocks and water sources and the atmosphere and types of precipitation and things like that. These are nonliving characteristics of an environment, and they're gonna be found across different areas of the planet. So they are very distinct areas of our planet. So very, very large communities of organisms and their environment. It's important to realize that a biome can contain different ecosystems. A biome is not an ecosystem. An ecosystem is found within a biome. So a biome can hold many ecosystems. For example, a great example of a biome would be a marine biome, so a salty aquatic biome. And this may include many different ecosystems, like a coral reef ecosystem, an open ocean ecosystem, maybe a shoreline ecosystem, or a kelp forest ecosystem. Maybe those are all in the same biome, but there may many different ecosystems. Remember that an ecosystem is the interaction between living organisms and their surrounding very specific environment. And those interactions can be found in a much larger biome. So just remember that this is different from ecosystems. Ecosystems can belong to the same biome, but they might be different ecosystems. So biome is bigger than an ecosystem. Okay? Now it's important to understand that the ecosystems and biomes are constantly in a state of disturbance, meaning that they are constantly changing. And there are temporary changes in the environment that can change the way a particular ecosystem works inside of that biome. These are constantly happening because, obviously, our planet is never static. It's always dynamic. Something is always changing. And for things like global warming, these are dramatically changing the ecosystems and the biomes that they are a part of. So if you look at this really beautiful map that we have of the continents of our planet, you can see that the biomes are going to be depicted in different colors. So you can have the tundra in this kind of teal color right here, the tundra. You can have a grass savannah in this light green. And then there's also, you know, the dry steppe or the arid desert. These are all different types of biomes, but they may contain different ecosystems within them. Now whenever you're looking at a biome, what are scientists trying to understand about that particular biome? So the things we want to discover when we are investigating a biome is we want to understand the biomass that that biome creates or that biome holds. What is biomass? So biomass is going to be the total mass of organisms in a given area. So the entire mass, all of the bodies of the living things in a particular biome or ecosystem. So if you're looking at the biomass of a of an ecosystem, you're looking at the actual mass or all of the bodies of every living thing inside of that ecosystem. Now granted this is probably we can't actually determine this. Right? We are not gonna go through and pick out every single organism and determine their mass because this is also gonna include a lot of microscopic organisms as well. So it's almost impossible to do. Right? So we estimate this, and we're going to estimate this via understanding the above ground biomass. So all of the living things that exist above ground that are very easy for us to see because, obviously, there are organisms that live inside of the dirt. Right? A lot of microbes live inside of the dirt. You're gonna have burrowing animals. You're going to have things like earthworms and molds, and you're gonna have the roots of trees and plants that are all down there under the earth, which would be incredibly difficult for us to measure. So we use the above ground biomass to kind of estimate the entire biomass. So again, the above above ground biomass is gonna be the total mass of living plants and organisms, excluding the roots and excluding the other organisms that live inside of the dirt. So we're going to estimate the biomass utilizing the above ground biomass, and we're also going to measure something important called the net primary productivity or NPP of a biome or of an ecosystem. Now why would we measure this? What are we measuring? Basically, you're measuring the productivity of a biome or an ecosystem. You can do this for ecosystems as well. So what are we looking at? So in net primary productivity, what we are measuring is the rate that plants in an ecosystem produce energy minus the energy that they consume during cellular respiration. So basically, this is going to be the energy plants make. So what is the energy that plants make? How do they make energy? Remember, they do the process of photosynthesis. They are going to make sugars utilizing sunlight energy via carbon dioxide and other things. So this is actually measuring photosynthesis. So, the energy that plants make minus the energy that plants utilize. Because remember, yeah, plants make their own energy, but they also have to utilize that energy as well. They also do cellular respiration. So this is looking at cellular respiration. Now how would we measure this? How do you measure the amount of energy that a plant uses and the amount of energy that a plant makes? How do you determine the NPP of an ecosystem? Well, the way that we're gonna do this is we're going to utilize the above ground biomass estimate, and we're going to determine how much c o two these plants take out of the atmosphere for photosynthesis versus how much c o two the plants put back into the atmosphere for cellular respiration. Remember photosynthesis, the creation of energy, takes c o two out of the atmosphere, and cellular respiration utilizing that energy is gonna be putting c02 back into the atmosphere. So this is gonna be the amount of c02 taken from the atmosphere minus the amount of c02 put put back into the atmosphere. That is gonna be how we estimate the NPP normally. This is normally how we are going to estimate this. Now why would we care about the NPP? Well, the NPP is going to tell you how a biome or an ecosystem is functioning. Obviously, if the net primary productivity is very high, there's a lot of photosynthesis going on. Maybe there's a high amount of plants in this area. Maybe we're looking at the tropical Amazon rainforest. The NPP of that forest, very, very, very high. Right? It's a very productive environment. While you could be looking at the, I don't know, maybe a certain particular forest in winter, that productivity is not gonna be very high, especially a forest in North America in winter when all the leaves are gone. There's not gonna be very high productivity because there's not a lot of photosynthesis happening. So NPP is definitely tied to the season and the location of that particular ecosystem, and it's going to tell you the health of that ecosystem as well and how productive the plants or the primary producers of that ecosystem or biome are functioning. So this is very important for the health of the biome and the ecosystems within it. Okay, everyone. Let's go on to our next topic.
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Terrestrial Biomes and Tropical Rainforest
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5m
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When we look at terrestrial biomes, we're gonna wanna consider both the biotic and abiotic factors. And we'll notice that what constitutes a biome is gonna be a similarity in those biotic and abiotic factors. Even if biomes might be separated by oceans, I mean, for example, Taiga, which you find across North America and across Eurasia, is separated by an ocean, yet it's still considered all part of one biome. Now, the abiotic factors we're going to really wanna look at are temperature and moisture, but we're also gonna wanna consider sunlight and wind as well. And the reason we're really gonna wanna focus on temperature and moisture is that biomes tend to be adapted to very specific moisture and temperature ranges. Likewise, the average temperature and precipitation, as well as the annual variation in temperature and precipitation, is gonna have a major effect on what life forms we find there, you know, what species are present. When talking about biomes you also might hear, 2 terms come up that I wanna kind of throw out real quick. 1 is ecotone, which is basically a transition between biomes, like a transitional area. And remember we said biomes, you know, they don't have national boundaries, they they're not just like completely isolated areas, they bleed into each other. And so you have transitional zones between biomes. Also, when we talk about the plant community in some biomes we're gonna we might refer to the canopy. The canopy is just the above ground portion of plant community. I mean, remember there's a lot of action going on under the dirt. That's where all the roots are. That's where all the fungus is helping those plants survive. So, you know, when we talk about the canopy, we're talking about just the above ground portion. And really, you're mostly gonna hear that when talking about biomes that have a lot of vertical growth. Now, here you can see a nice, really nice figure, that shows the, you know, the difference, basically, in annual precipitation and annual, average temperature in various biomes. And, it gives you a really nice idea sort of of, you know, how these biomes might transition between each other. So you can see, you know, very cold with low rainfall here is tundra, and kind of on the opposite end with a lot of year round warmth and rainfall, we have tropical rainforests. And we're gonna talk about both of these biomes. Actually, we're gonna talk about tropical rainforest right now, spoiler alert. So tropical rainforest is going to be located in the equatorial region, sometimes called the tropics. Wonder why? You can see that band cross here. Oh jeez, I cut off Madagascar, I can't cut off Madagascar. There we go. So this band is, right around the equator. And in these tropical rainforests we're going to have lots of moisture and warm temperatures year round. There's gonna be really, like, very little seasonal variation in temperature in these regions with some variation precipitation, but they're still going to be receiving precipitation year round regardless. Now the plants in these communities are going to be vertically layered, hence, the term canopy. They're going to, you know, have a variety of strategies to fight for light, let's let's say. Because the plant growth is so vertically stacked, you know, everyone is trying to use every little bit of light they possibly can. So there's very intense competition for light. Now the trees in these forests are gonna be what we call broad leaf, and that basically just means they're angiosperms that have broad flat leaves, and they're also going to produce seeds surrounded by fruit. Now we also call these evergreen forests because, well, since there's little to no seasonal variation, they're green all year round. And what you really need to know about the tropical rainforests of the world is that they are so rich in species diversity. They're also incredibly productive areas. I mean, they don't cover, you know, a ton of the Earth's surface, but they hold, you know, what's estimated to be like nearly half the species on the planet. Additionally, they're gonna be responsible for large, large amounts of productivity, which means drawing a lot of carbon dioxide out of the air. And with that, let's go ahead and flip the page.
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Desert and Savanna
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Deserts tend to be around 30 degrees latitude north and south, basically just outside of that tropical region, and they're usually found in the interior of continents. Now most people tend to think of deserts as just being really hot all the time, When in fact, the temperature in deserts is highly variable, both seasonally and daily. In fact, temperatures can vary by as much as 40 degrees Fahrenheit in a given day. Could you imagine going from 80 degrees during the day to 40 degrees at night? I can't even imagine temperature changes like that on a daily basis. Now we also know, hopefully, from our discussion of the Hadley cell, why rainfall is so low in deserts. Right? Because of those atmospheric circulations that are causing all the precipitation to get sucked up by the tropics, so that none is left for those poor deserts. But they're surviving. Right? In fact, there is lots of life in the desert. Now, there's not a ton of vegetation. It tends to be mostly scattered with lots of bare patches of earth. However, there is some. It doesn't all look like this sea of dunes you see here in this image. And most organisms that live in deserts tend to have water conservation adaptations. So for example, reptiles, which are common to deserts, have scales made of keratin, which creates an impermeable barrier for water and helps prevent water loss from the body. Maybe even more famously are cacti, which have adaptations that allow them to store fluids in their body. And additionally, it should be noted that animals have learned to exploit those storage abilities of cacti, so life is ever evolving. Now here we have this nice global map, lets us, see the major deserts distributed across the globe. And really all I I want to point out is just, you know, how you can see that you have that tropical band in the middle, and then desert on either side of that, and you know, show you over here. So, you know, this is tropical region, and then we have desert, and more desert up here. Of course, there are exceptions, there's always exceptions, but just as a general trend, something to bear in mind. Now, savannah is a biome that usually occurs around the equator, and it's cool. It's kind of found as a transition zone between forest and desert, or forest and grassland. And that's why it tends to be mostly made up of grasses with some small woody plants. However, it does have some scattered trees, as you can see in this picture here. Of course, you wouldn't call that a forest by any means, but there are some trees. Now, the savannah will or rather savannahs will usually be found around the equator, and their rainfall will be highly seasonal. They have In fact, they can have dry seasons that can last, you know, most of the year, almost the whole year. Because of that, the plants of the savanna have to be drought tolerant as it could be a really long time before they're gonna see any rainfall. Also, because the dry season can last so long, wildfires are fairly common, which is why most savanna plants are also fire tolerant. I mean, if you can't regrow from, you know, your average regular run of the mill wildfire, you're not gonna last long here, kid. So with that, let's go ahead and flip the page.
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Temperate Grasslands and Forests
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Chaparral is a biome primarily found in California and Baja California. This is basically just scrubland, so little shrubby plants like you see in this image here, where, you know, rainfall is gonna be highly seasonal, and you're also gonna have regular fires, which is gonna mean you're not gonna have a lot of tall trees. Right? Now it is usually found at mid latitude coastal regions, hence, California and Baja California. However, you will find it in other parts of the world. It's just most common to there. Now temperate grasslands are kind of like oceans of grasses, basically. They're these, you know, big plains of grasses and they have dry winters, meaning not a lot of precipitation in the winter, and lots of precipitation in the summer. And temperate grasslands include the Eurasian steppe, which is a massive massive grassland that spans both, well, it's kind of spans a large part of the Eurasian continent. I was gonna say it spans Europe and Asia, but, you know, I I don't like making those distinctions because it is just one landmass, and also you'll find it in the North American prairie. Now we call it temperate because it falls into the temperate zone, which is basically the zone that lies between the tropics and the polar regions. And it's characterized by moderate temperature fluctuations, so not a lot of extremes here. Now, broadly forests, or rather temperate broadly forests are gonna be found mainly in the Northern Hemisphere, and they're gonna be dominated by deciduous trees. And, you know, the temperatures they can vary moderately. You will see, you know, snow in the winter and hot summers, but these aren't super extreme, you know, seasonal variations in temperature. And you'll also see moderate precipitation year round in these environments. Now, with that, let's flip the page.
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Taiga and Tundra
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Taiga is the largest terrestrial biome on Earth. It covers North America and Eurasia. It's absolutely mind boggling how much land area is taken up by taiga. And sometimes this biome is called northern coniferous forest or perhaps boreal forest, and really it's dominated by conifers. And the reason for that is because conifers are both cold tolerant and water loss resistant. And hopefully, you can see by how far North this biome is, it's gonna get very cold there. Additionally, drought is common, which is why the waxy needle like leaves of conifers are well suited to this biome. Now the Arctic Tundra is the northernmost terrestrial biome. It basically runs along the, northern edge of the, the northern edge of the land masses in the northern hemisphere. And year round it is cold, it's super cold. In fact, it's so cold year round that it has what's called permafrost, which is basically soil that remains frozen all year round. It also has very low precipitation. So this is clearly not an easy place to live, yet life finds a way as you can see from this image behind me. Now, I don't want to harp about global warming, but I do want to say that the amount of permafrost, that is the area that is, considered permafrost, has been shrinking, at a pretty alarming rate due to global warming. Now with that, let's go ahead and flip the page.
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Aquatic Biomes
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Aquatic biomes include both freshwater and marine biomes and will be characterized by salinity and light penetration, unlike terrestrial biomes where we were mostly looking at temperature and precipitation. Now salinity, you can just think of as saltiness of the water. However, technically, salinity is a measure of dissolved solutes in a solution. And, really, what you need to know is that this is gonna have a profound effect on osmosis and water balance in organisms. Now the water depth is going to affect the availability of light. It's also gonna have an effect on pressure and temperature, but we're gonna focus on light right now. So the upper regions of a body of water are considered part of the photic zone. This is basically the depth of water that receives enough light to carry out photosynthesis. As you can see in this, chart right here, the photic zone is not very deep at all. It's, or rather compared to the other zones, it's pretty shallow. The aphotic zone is going to be the portion of water below the photic zone, and it's going to receive little or no sunlight. And the deep deep depths of the a photic zone are called the abyssal zone, which is basically the deep depths of the ocean that don't ever see the light of day. There's no light there ever. They are in perpetual darkness, and this actually will have a really interesting effect on the organisms that live there. Now, in addition to depth affecting the penetration of light, the cloudiness of a fluid can also have an effect. Now we call this cloudiness in a technical sense, turbidity. It's basically just a fluid being cloudy due to suspended particles. Now I'm gonna jump out of the way. Here, you can see 2, 2 bodies of water converging, and there's a line between them. Right? So here's one body right here, and here's body number 2 over here. You can see the literal line of convergence because of how turbid this water is. Right? It's just a ton of suspended particles in there, giving it that color. But turbidity is also going to diminish the ability of light to penetrate. Now, some more, definitions about, you know, regions in, these aquatic biomes will sometimes use the term littoral zone, which is basically the area of a body of water that's still close enough to the shore that sunlight will penetrate through to the bottom. So, you know, in our image here, for all intents and purposes, let's just call this region the littoral zone, since these plants right here are still getting enough light for photosynthesis. So, you know, it's the light is gonna make it all the way to the bottom to these plants right here. Now the pelagic zone is basically water that's not close to the shore, not close to the bottom, and is going to actually comprise, parts of or, well, the photic zone and parts of the, a photic zone as well. So the pelagic zone, you can see, is, you know, kind of just like this region. Oops. I drew my line too far down. It's not the bottom. It's like this region here. It's just the, you know, just water. Open open water, let's let's say. Now underneath this, you have the benthic zone. It's like the lowest level of body of water. Sometimes you might hear it called the seabed, and this is going to both include the sediment and some subsurface regions. So the benthic zone is kinda all this biz in here. And organisms that live in the benthic zone are called benthos, and they're well, the benthic zone is going to be particularly rich in what's called detritus or detritus. It's just debris or waste. It's usually dead organic matter, and it's particularly abundant in the benthic zone because anything that dies above the benthic zone is gonna sink down in the water and find its way to the benthic zone. There are gonna be a lot of organisms living in the benthic zone that actually eat and recycle this dead organic matter. So, with that, let's actually go ahead and flip the page.
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Temperature in Aquatic Biomes
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The movement of water can have a dramatic effect on the organisms that live in it. In fact, take for example the river dolphins that have evolved to sleep in one hemisphere of their brain at a time. Totally bizarre phenomenon that allows them to live in these waters with currents. So, you know, if they were to sleep in both hemispheres simultaneously, they probably get smashed around by the water currents, you know, could end up dying, for example. So this is an adaptation based on the movement of water. Now the movement of water is also going to affect nutrient availability, and we're gonna take a look at that in just a second. I do wanna quickly mention plankton, which are these small floating organisms in water, mainly made up of diatoms, which you can see here, and protozoans as well as crustaceans. And these guys are going to be a very important food source in aquatic biomes. Now speaking of that nutrient availability, the deeper waters tend to be richer in nutrients because all of that dead organic matter is gonna sink to the benthic zone, and so that water is going to have more nutrients. So ocean upwelling is this interesting phenomenon where nutrient rich that nutrient rich water from the depths will rise up and replace surface water that's moving away from coasts, in this way adding more nutrients in to, the system. Now, thermoclines are pretty, I guess, you could say bizarre phenomenon. They kinda go against our common experience, you know. If if we're looking at a body of water we kind of would expect that the temperature would just go down with depth. However, you can sometimes have these distinct layers called thermoclines that will actually separate deeper colder waters from warmer surface waters. And in the thermocline, you're gonna have this really abrupt temperature change. So notice here that, our y axis axis on this chart is depth, and our x axis is going to be temperature. Notice that in these deeper depths, for example, as we go down, there's very little variation in temperature. Right? It's just like from there to there, you know, very small variation in temperature. However, up here, you have this rapid drop in temperature. Right? Barely go down in-depth at all, and yet we're experiencing a massive temperature change. That is a thermocline. So this horizontal line that I've drawn across here is representing our thermocline. It's that that band where an abrupt temperature change happens, and it's gonna separate these warmer surface waters up here from these colder waters of the depths. Now water temperature can actually also lead to nutrient rich water from the bottom coming up and enriching the, water closer to the surface. This is actually something that's gonna happen in lakes, it's an event known as lake turnover, and it's going to be due to seasonal temperature changes. So in the winter, we'll, you know, assuming let's just say this is like a, you know, smaller body of water, like a smaller lake, will have ice covering the top. And, surprisingly, that's actually gonna be colder than the water below. The water below will actually be a little warmer than that surface water. Now, during the spring we'll have, our first turnover event Because as the ice melts and as, the ice melts into the water it's going to cool it and that cold water is going to sink. That warmer water that was at the bottom, that nutrient rich water is gonna rise up and move towards the surface. So we're gonna have some mixing of nutrients. Now in the summer you're going to have a much more dramatic temperature gradient through your, lake. You know, it's gonna be fairly warm at the top and, you know, roughly unchanged at the bottom. But what's gonna happen during the fall is, as that surface water cools, it's going to sink, move down, and cause some of that nutrient rich water from the bottom to come up. So this, seasonal turnover will actually happen both in fall and spring, and it's going to cause, you know, some mixing of the more nutrient rich water from the bottom with the surface waters at the top, and we're getting this, cycling of water due to these temperature changes. So with that, let's go ahead and flip the page.
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Freshwater Biomes
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Lakes and ponds are standing bodies of water that will have variable salinity, oxygen concentrations, and nutrient availability. On one end, you'll have oligotrophic lakes, which have low primary productivity, meaning not a lot of photosynthesis going on, because they have poor nutrient content. However, these lakes tend to have high oxygen concentrations. On the other end, you'll see eutrophic lakes, which have high primary productivity because they have high nutrient concentrations. However, these usually have low oxygen levels, and I'll explain why. Now not all eutrophic lakes start out eutrophic lakes. Some, lakes undergo eutrophication, as it's called, where nutrient rich stuff gets into the lake. Often, you'll see, you know, nutrient rich fertilizers, on agricultural lands or something, getting into the runoff water and finding their way into a lake. And they'll just inject a bunch of nutrients into the lake, which will lead to an explosion in primary productivity. So, you know, like a big algae bloom or something to that effect. All of this new plant matter, or I should say photosynthetic organisms, you know, it's gonna be a lot of algae, All of these, new photosynthetic organisms are going to eventually die, which is going to feed the decomposer populations. Now all of those decomposers are gonna eat all the dead, you know, algae and whatever, and they're going to consume oxygen in the process. So basically, you know, the high primary productivity leads to high amounts of decomposition, which are going to lead to low oxygen levels. Now most of the plants that you'll find in lakes and ponds are gonna be in the littoral zone, and that's because this is gonna be the area that gets the best light. Remember, light will penetrate all the way to the bottom of the littoral zone. And bordering the littoral zone is what's known as the lymnitic zone. This is basically like this surface waters away from shore of a lake. Now lakes and ponds also, I should mention, have a benthic zone, just like all aquatic, biomes, and this benthic zone is going to, you know, have lots of sediment, and dead organic matter, and be fairly, you know, nutrient rich if it has lots of dead stuff in it. Now wetlands are an amazing biome. You know, we often over overlook them or kind of write them off, because we're just like, they're just bogs or swamps or marshes, you know, gross. Right? Well, actually, they're really important because they're have this amazing ability to filter pollutants from water. They're kind of like nature's Brita. They basically yeah. I mean, really, like, they, you know, they clean water making it potable. Now wetlands are basically just land that's been saturated with water, and it doesn't have to be permanent. You know, they can be seasonal, like they get inundated with water, on a, you know, some sort of regular seasonal basis. And what you'll see with wetlands is they'll, you know, they'll they'll often have a lot of what's called emergent vegetation. So here, you know, kind of just like encircling the, more watery part. Right? And you'll see you've got some lily pads here and here on the sides. Right? Those are all like floating plants. This stuff all around, that's what we call emergent vegetation. It's gonna, you know, shoot its roots, or rather it shoots up, out of the water and, you know, have a portion of its body be above the water's surface. So, you know, you often see things like cattails and grasses and that sort of stuff, that sort of emergent vegetation in wetlands. Now streams and rivers are going to be, flowing bodies of or flowing water, and usually they're gonna be headed toward an ocean, or a lake, or some other river. So, you know, they'll join together and eventually that river will go to some lake or ocean or something like that. Now what characterizes these biomes is the volume of water flow. How much water is flowing. Right? Do you have just, you know, a little trickly stream, or is this a rushing torrent of a river? And, you know, one interesting thing to note about water flow is it will actually affect the oxygen content. So faster flowing water has lower oxygen levels in general. Now when a river meets the sea it can form an estuary. This is a semi enclosed body of brackish water, brackish water meaning a mix of fresh water and salt water. And it's basically a transition between rivers and the ocean. And here you can see an estuary that's part of the Amazon. So this is the Amazon or, you know, the, estuary of, part of the Amazon river coming in and meeting the Atlantic Ocean here. And with that, let's go ahead and flip the page.
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Marine Biomes
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Oceans are massive bodies of salt water that cover the majority of Earth's surface, and ocean biomes have some special terminology we should go over. Now the Littoral zone of oceans is a little different. You see, the water line where oceans meet the land is not fixed. Oceans have a tide, so the water level will actually flow from the high tide point to the low tide point, and this area, this littoral zone is called the intertidal zone. And here, we're looking at it, you know, as a beachhead, but sometimes these intertidal zones will actually be rocky and can have verticality to them, and they can also have depressions that water gets trapped in that we call tide pools. And tide pools can be incredibly rich and diverse, ecosystems. Now the area that extends out from the littoral zone or the intertidal zone is called the neuritic zone, and this is basically just shallow ocean that covers the continental shelf. Now the continental shelf is the extension of land that comes off of contents, rather continents, that goes underwater. So, you know, imagine, if you were to pull the continent out of the ocean a little bit, you know, this would just look like a continuation of the land mass. Now at the edge of the continental shelf, you'll have a sharp drop off, and there is where you get open ocean. Scary stuff. The open ocean or the zone, of open ocean is called the oceanic pelagic zone, and it's just what's beyond the continental shelf. Now the benthic zone in oceans is going to be, you know, markedly different from the benthic zone of a lake, for example, because oceans are so much deeper and more vast. Now, the marine benthic zone as it's called, or sea floor if you prefer, is basically in darkness always. Now coastal areas will receive light if, you know, they're, the, benthic zone is shallow enough. However, the majority of the marine benthic zone is going to be in total darkness. Now coral reefs are, you know, it's hard to oversell them. They're just incredible ecosystems, and, you know, they're such a rich biome in terms of species and in terms of, you know, the sort of services they they provide to the areas around them. And here's a map, you can see the location of coral reefs all over the world. They're going to be built by coral, which are these little animals that secrete these structures made of calcium carbonate. It's probably what you picture when you think of coral. And those calcium carbonate structures are, you know, probably look at them and think of them as rock or something. It's actually not rock, but, you know, you can see these structures here in this, this mass of coral. Now the reason I bring up calcium carbonate is because coral reefs are super threatened by ocean acidification. Calcium carbonate will readily react with acids because carbonate is a base. So even a small increase in acidity can result in great damage to coral reefs, and you can see it from satellite photos, you know, looking at the Great Barrier Reef, see just how much of that has been eroded. The last, biome I wanna talk about are these deep sea hydrothermal vents. These are fissures in the Earth that release geothermally heated water, really, really, hot water. And there are two reasons I wanna bring these up. 1 is because they're potentially the source of life on Earth. Here, you can see what's called the lost city. These are a special group of hydrothermal vents that form these carbon stacks, and it is, it has been proposed that, life may have started in the little nano tubes in these carbon stacks. I'm not gonna get too much into the details, but, you know, it's cool stuff. It's a very interesting theory whether or not you believe it. Now, this is the other reason I wanted to bring up these hydrothermal vents because they have some really interesting ecosystems, or rather say communities of organisms that have developed, there. You see, pretty much everywhere we've been talking about up to this point, has been a community that's more or less supported on photosynthetic organisms. But these communities are not supported by photoautotrophs, but by chemoautotrophs. They're supported by bacteria and archaea that can, you know, essentially fix carbon from the, you know, from performing various chemical reactions with the inorganic, compounds avail or, sorry, not inorganic compounds. The compounds available to them from these hydrothermal vents. Basically, they're just very cool ecosystems because they're so different from, like, everything else we see. You know, it's, they're super unique in that there's, like, a very rich diverse community built on top entirely on top of chemoautotrophs. You know, we're so deep down, there's no photosynthesis happening here. So very cool stuff. Now that's all I have for this, lesson, I'll see you guys next time.