Okay, everyone. In this lesson, we are going to 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 basically a very large community of organisms and their environment. 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 flora and fauna and abiotic factors. Remember, these are nonliving factors. These are going to 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 going to be found across different areas of the planet. They are very distinct areas of our planet. 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 be 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. 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 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 going to go through and pick out every single organism and determine their mass because this is also going to 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 going to have burrowing animals, you're going to have things like earthworms and molds, and you're going to 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 going to 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 going to do this is we're going to utilize the above ground biomass estimate, and we're going to determine how much \( CO_2 \) these plants take out of the atmosphere for photosynthesis versus how much \( CO_2 \) the plants put back into the atmosphere for cellular respiration. Remember photosynthesis, the creation of energy, takes \( CO_2 \) out of the atmosphere, and cellular respiration utilizing that energy is going to put \( CO_2 \) back into the atmosphere. So this is going to be the amount of \( CO_2 \) taken from the atmosphere minus the amount of \( CO_2 \) put back into the atmosphere. That is going to 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 going to be very high, especially a forest in North America in winter when all the leaves are gone. There's not going to 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.