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- [Voiceover] So, just as a bit of review. If we take the members of a certain species that share the same area, we call that a population. Population. All of the organisms in this particular population will be members of the same species. There could be other members of that species that aren't in that same area, and they wouldn't be a member of this particular population. And a certain area won't have just one, or it doesn't tend to have just one species in it. So, we could call this population one. You might have other populations there of a different species. So, this is another species right over here. All of them combined in the same area, we could call this population, population two. And if you take... And we could, obviously have many more populations there. And if you take all of the populations in a given area, there's flexibility on how you define that area or define that region, you take those together, so you're really taking all of the living things in a certain area, we call that a community. A community of populations. Now, the community only consists of living things, the biotic factors. So, let me write that down. Biotic referring to the living things in a certain area. But if we want to think about not just the living things, but also the non-living things in that region. So, I'll write abiotic. Let me do that in another color. So, let's take the abiotic factors, or the abiotic environment. And, once again, we're sharing the same region, and that is flexible on how you define that region. You put all of these things together, and then you get your ecosystem. Your ecosystem, once again, it could be a very small region, it could be a very large region, but it's made up of all living things, the biotic factors, and the non-living things, the abiotic factors. Now, what we're gonna think about in this video is just the types of ecosystems that you might have. Think a little bit about it, and also begin to think about how the different factors interact with each other. How there's conservation of matter where, within an ecosystem, matter tends to go from one form to another. You also have a flow of energy. Energy tends to enter an ecosystem in form of light, and that energy gets transferred from one organism to another, and, sometimes, even involving the non-living things, eventually, getting turned into actual heat. Now, in terms of the types of ecosystems. I already mentioned there's a lot of variety there. This, right here, is a picture of a tide pool at Half Moon Bay, not too far from where I live. I've actually been to the tide pools at Half Moon Bay. And you could consider one particular tide pool, both the abiotic factors, the water, and the rock there, as well as the biotic factors, the starfish, the sea anemones, and whatever else might be living there. Those combined, that could be an ecosystem. You might say that the entire beach is an ecosystem. You might say that the entire region is an ecosystem. Once again, it depends on how much you want to zoom in or how much you want to zoom out, and you can zoom out a good bit. This rain forest, right over here, this is the Amazon rain forest. You can consider the whole rain forest an ecosystem, or maybe you just want to study, maybe you just want to study what's happening in this exact region, right over there. You can also consider that an ecosystem. You can consider what's happening in the river, itself, an ecosystem, or, maybe, one part of that river. And, as you notice, I'm talking about some ecosystems that are on land, and some that are in water, and that is a general way, one way of classifying them. So an ecosystem, you could have it on land. You could have it on, near, in the water. So, you could say it's aquatic. And then, if within aquatic, you could have ones that... You have salt water, or partially salty water, and these are called marine, and the main marine ecosystem, we're thinking about the oceans and things like that. And then, you have freshwater ecosystems. Like if you are in the upper-Amazon, that is freshwater that is flowing. So we could say fresh, freshwater, non-salty water. And even though it looks like rivers are big and there's a lot of freshwater around us. Obviously we need freshwater to live, most of the aquatic ecosystems are marine, are not involved freshwater. Freshwater is a very small subset. Now, this is just a few examples. Even your body, you could view your body as a whole ecosystem. You could view parts of your body as an ecosystem. You could look at just... You could look at just a fraction of... If this is my hand right over here, you could take just a little square, there, and you could consider that an ecosystem. You can think about the different bacteria that are there, other types of microorganisms that are there, and how they're interacting with the non-living things, the air. How they're interacting with the oil on your skin, with the dead skin cells, and also, how they're interacting with the living skin cells, and you, yourself. Now, since we're in the, since we're focused on how we can classify ecosystems, one thing that's often done is classifying land ecosystems into various categories. And, right over here, we have depicted the major types of land ecosystems on our planet and where you might find them. And these different types of land ecosystems, these are called biomes. Biomes. And as you can see from this diagram, tropical forests, you can find it right over here. This is the Amazon rain forest. You can find it in Africa. You can find it in Southeast Asia. You can find it in Central and even Southern or North America. You have boreal forests which you'll find in more northern latitudes. Savanna, desert, tundra, chaparral, polar ice, temperate forest, temperate grasslands, and these are just helpful for thinking about roughly the types of ecosystem, or ecosystems we would find in those regions. And it's typically most determined by temperature, moisture, the climate. Actually, the climate and the terrain and the types of minerals that you would find there, that tends to be a pretty good indicator for what it will be like, what the life would be like. But even with that said, there could still be a lot of variety. For example, the Sonoran Desert, that is right over here in the southwest United States, in the northwest Mexico. This is a desert, and there's deserts all over the rest of the planet, but they won't have... They might be similar in a lot of ways, but they won't have the exact same climate, or the exact same abiotic factors, or the exact same biotic factors. So, for example, right now I'm gonna show you a picture, pictures of the Sonoran Desert and the Rock Desert that's on the island of Boa Vista. Boa Vista is right over there. You really can't see it. It's a very small island off the coast of Africa. And, as we see in these diagrams, or in this picture, you don't have to be an expert to recognize that, okay, these are both deserts. They both look dry. There's not a lot of water here, but they are also very different. The Sonoran Desert looks to have at least a lot more life, than the Rock Desert have here. It's appropriately named the Rock Desert because it seems, at least to the naked eye, it looks like all you can see is rock. So biomes, once again, it's a very rough, high-level way to classifying land ecosystems. But even the same biome can be very, very... Two things that are categorizing in the same biome could be very different.