Understanding Ecosystems and Interdependence

What you are looking at here is something called a food web. It's a tool that scientists use to help them understand environments and how organisms relate to each other in environments and how they might be impacted by the environments. This right here is going to be at the core of this unit, the ecosystem unit. Now ecosystems are pushed very heavily in seventh and eighth grade in Florida so Hopefully this is something that you already have a very strong foundation of and will already know a lot about. And we can just build off, build on top of it for what we're learning for our class. All organisms on life or some are on the planet are in some way dependent on other organisms. We call this interdependence. They could not exist without the presence of other organisms. Take humans for example, we have to get our oxygen from plants, we have to get our food from animals and plants, rely on animals and plants for our clothes. Every single thing that we do is reliant on other organisms. When scientists look at organisms, they actually classify all organisms into different levels. Not just the classification that we learned about, but classification of what the organism's role is in life. And the lowest level of organization is going to be the organism or the individual. And when we get all the individuals that are like each other in a similar area, we're going to call that population. It's like all the humans in Jacksonville are the Jacksonville population. And then the community is going to be all of the organisms that exist. inside a certain location that are regardless of whether they're the same organism or not, right? So like all the humans and all the dogs and all the cats and all the birds and all the mice and all the bugs inside Jacksonville would be the Jacksonville community. The ecosystem will be all the living and non-living things that are in Jacksonville. So that includes like the houses, the roads, and then if you take all of life. that lives in the same area, like the same type of climate, the same type of weather conditions, that's going to be our biome. And finally, all life that exists on Earth is going to be the biosphere. And here's a summary of that. Now hopefully you should be aware that not all organisms in an area are the same. In fact, there's lots of different variation of organisms in different areas. And this is referred to as biodiversity, which is basically the amount or number of different organisms in an area or in a location. And biodiversity is a very key thing because the more biodiversity there is usually, the more biodiversity there is. The more interactions you have going between organisms and the more stable that community is, that ecosystem. If there's only a couple organisms in an ecosystem, you can knock one organism out and the ecosystem could struggle. But there's lots of different organisms in an ecosystem. One or two organisms that are infected would not have a huge impact on the ecosystem. So in general, when you're talking about biodiversity, if you have more biodiversity, you're going to have a more stable ecosystem. So what are some things that could affect the ecosystem or can in some way impact either positively or negatively the biodiversity of an ecosystem? Well, first of all, we have what are called abiotic factors. A means not, and biotic, or bio, means life. So these are factors, things that are not alive. So as the example shows, soil, pollution, natural disasters, climate, the type of minerals in a location. Anything that's not made of cells, that's going to affect the location. It's going to be an abiotic factor. And then there's also biotic factors. What are the organisms that live there? If there are certain predators in the area, you will not have certain organisms. If there's... A certain competition will not have other types of organisms. So these biotic and the abiotic factors are both going to have an impact on the ecosystem. So, look right here. What in this picture is going to be biotic and what will be abiotic? Well, what's made of cells? If you look at the plants, the phytoplankton, the fish and the turtle and the fungi, those are all made of cells. Those are all going to be biotic factors. The water, the sun, the air, the sediment, those are all not made of cells. Those are going to be abiotic factors. They all have an effect on that ecosystem. Now, the particular ecosystem in an area is going to be referred to as its habitat. This is a place where a particular population of organisms is going to reside. And habitats are affected by both biotic and abiotic factors, and they can be very diverse and very specific to organisms. Here's just three other examples of your habitats. Now, when it comes to an ecosystem, an ecosystem is not just a whole bunch of animals and organisms that randomly happen to be living together. Because it's interdependence, because every organism is in some way impacting another organism, the organisms and ecosystems are very specific. In fact, an ecosystem is usually a type of niche for specific organisms. And the reason this is the case, the reason that ecosystems are very specific about the organisms that are there and how they can survive and what they can do there, is because it's really all about energy. Energy is a very valuable resource. Life cannot make its own energy. We have to steal it from the sun. And so energy is very limited in reality when it comes to it being available, even though we don't really feel that because we always have lights on and we're always driving around. When it comes to the amount of available life on the planet, energy is a limited resource. And in fact, we're going to look at a couple other resources too, like carbon and water and oxygen. And all of those things, if an organism were to use them and destroy them and make them not available for any other life, life would die very quickly on Earth. So instead of what life has done is it's adapted to where it's constantly moving energy and resources. and nutrients from organisms that don't need it anymore to organisms that do need it. So as long as I'm alive, I'm going to be taking energy from plants. I'm going to be grabbing oxygen and carbon and nitrogen from different sources. But when I die and I don't need those anymore, the ecosystem is going to make sure that all those nutrients are taken from me and given to another organism that can use them. So when it comes to the roles of animals and organisms in ecosystem. The reason they're so important, the reason they're so well defined, is because it's all about the energy flow in the ecosystem and conserving and preserving all the different nutrients available in ecosystems. So what are the different roles in ecosystems? Well, first, there's what are called producers. We call these things producers because they produce the energy that you and I can use. They're autotrophs. They can make their own energy, and they use sunlight to make that chemical energy, the sugar. And then they use that sugar for all of life processes. And all of life is dependent on these producers. Life could not exist without them. Next, you have a consumer. And consumers are heterotrophs. Hetero means other, and troph means energy. So we get our energy from others. We cannot make energy from the sunlight, and we have to eat other organisms for energy and nutrients. Once again, though, that sugar, we have to use it for life processes. So we use sugar for the same reason that plants use sugar or producers use sugar. We use it for life processes. And producers, just so we're clear, like they're mostly plants, but you can also have bacteria that are producers. Any organism that can do photosynthesis can be a producer. So some producers are also going to be producers. So the consumers, the organisms that eat other organisms, get energy from other organisms, they use that sugar for life processes. Now right here I have a photo of a pitcher plant, and this is a carnivorous plant. This is a plant that eats animals. And what happens is you'll have a little animal climb up on the side like a rat, or sometimes even like a small monkey or a bug. And it will reach into the side, try to get something inside this pitcher, and it will fall down. And the pitcher is strong enough to actually capture it. and make it so the organism can't get back out. And there's little digestive enzymes inside this plant, which will then start digesting the organism. Very gross, very painful, but that's what the plant does. Now, this plant's funny because when it's eating the organism, it is a consumer. But at the same time, it can also do photosynthesis, so it can also be a producer. So depending on what role it is in the ecosystem, it can be both a producer or a consumer. But most organisms are either one or the other. Now there's many different types of consumers. It's all based off your level in the ecosystem. So this right here is a special type of graph that shows us the role of different organisms in the ecosystem. Here's those producers we were talking about that capture sunlight and turn it into energy. If you're an organism that eats the producer, you are called a primary consumer. Primary means one, so you're the first level consumer. If you're an organism that eats the first level consumer, you are a secondary consumer, right? Secondary refers to two or second. If you're an organism that eats the organism that eats the organism that eats the producer, you're a tertiary consumer and you can keep going up to quaternary, quaternary, sextonary, as far as you want. Most ecosystems, though, you really just go up to tertiary and quaternary consumers. You don't really go much higher. Think about like... us and cows. A cow is a primary consumer and eats the primary producer, and we eat the cow, so we are secondary consumers when it comes to the cow. But basically, consumers can have different levels, and the level is just determined by how far you are from the producer. If we eat lettuce, we are the primary consumer because we're eating the producer directly. Now, there's a third role in the ecosystem. These are heterotrophs. that are called decomposers. So decomposers, they actually eat or decompose dead things. And once again, what are they using that sugar for? For life processes. So we all use sugar for the same thing, the same reason, we just get it from different sources. And these could be fungi, they could be bacteria, they could be any different types of other organisms. But their job is to grab all those resources from dead organisms that the dead organisms are not using anymore. and use them for their life processes, and then put those resources, any spare resources, back into the soil, back into the circle of life. So these right here are really key. Remember earlier I was talking about how we want to make sure our resources keep cycling and keep circling, that when I die, the resources don't just stay with me, that they actually move and aren't used by other organisms. One of the keys to that is the decomposers, because they get those dead organisms, and they make sure the nutrients that I no longer need, are being moved to organisms that can use those nutrients. Now, in order to track how these nutrients flow or move through an ecosystem, there are three different types of models that scientists use. The first is called a food pyramid, and this shows a direct path of energy movement. So it says energy goes from the plant to the cow, to the fox, to the bear, right, or to the wolf, to the bear. from here to here. It never goes backwards, right? The bear doesn't get eaten by the fox, and the cow, the fox doesn't get eaten by the cow, and the cow doesn't get eaten by the grass, right? It just goes one direction. If for some reason the bear does get eaten by the fox, then we switch their places. Now what's really interesting about energy pyramids is that there's this 10% rule, which is just generally true in science, which says that if grass makes all this energy from the sun, Only 10% of all the energy that the grass uses goes to the cow. So let's say right here that the grass makes 1,000 units of energy. When the cows come and eat the grass, they're only collecting 10% of that available energy. So they're only collecting 100 units of energy. Where does the other 90% of energy go? Where are the other 900 units? Well, they're used for the life processes of... the grass. The grass has to do its normal life processes. It has cells. It has to work through, it has to keep the cells alive. They have to do their functions. And so most of the energy is going to be used for that. And only 10% is used by the cow. Now if you get all the energy the cow collects, and let's say it's 100 units of energy, when it's eaten by the wolf, only 10% of the available energy from the cow is used. by the wolf or collected by the wolf why is that well that's because the cow uses a 90 for its life processes for its survival for its cells doing things and this goes up the list each time you move up there's a 10 reduction in the available energy and that's why like we have lots of grass and lots of primary consumers but if you look in like a a area any area you're gonna have very few secondary and tertiary consumers because Most of the energy that is required to sustain a tertiary consumer is lost as it goes up the cycle. Think about lions in the African pride lands. You don't have very many lions relative to the amounts of grass and gazelles and other animals because most of the energy is used by the grass. And then most of that available energy is used by the gazelles when they eat the grass. And only a little bit of energy is available for the lions, so there are not very many lions. The food pyramid also shows really clear trophic levels and trophic levels are just the words that we use to represent the different labels for our consumers, our producers, and our decomposers. So the first trophic level right here is the producer and the first trophic level is always going to be your producer. Second trophic level is going to be your primary consumer, third trophic will be your secondary consumer, fourth trophic will be your tertiary consumer, it's going to go up until this pyramid ends. Here's just another example of the energy pyramid. Here you have rainforest leaves. And if you look, they collect 100% available energy. And the insect larvae come and eat the leaves. The insect larvae are only able to collect 10% of the energy from the leaf. The bonobo comes along and eats those little insect larvae and only gets 10% of the energy from the insect larvae, which is only 1% of the energy from the leaves. And the bonobo actually gets eaten by the crocodile. The croc dot only gets 10% of the available energy from the bonobo, which is only 0.1% of the available energy from the rainforest leaves. Alright, our second type of model is called a food chain. And this is, again, just a direct path of movement. It just shows energy goes from one thing to another, to another, to another. It's similar to a food pyramid, but it doesn't really show the amount of energy moving through the system. And it doesn't necessarily show the trophic levels, though it can. But it does tell us how energy is moving from one place to another. When you're looking at this, energy always moves from the end of the arrow to the beginning. Okay, so where the arrow is pointing, that's where the energy is moving to. So the energy is moving from the producer to the grasshopper. The energy is moving from the grasshopper to the frog. And the energy is moving from the frog to the snake. Okay, so this just shows where the energy is moving to. Our last type is a food web. And this shows... all the possible passive energy movement in a system. Once again, the arrows show where the energy is moving. So the rabbit eats the leaf, so the energy is moving from the leaf to the rabbit. The wildcat eats the rabbit, so the energy is moving from the rabbit to the wildcat. This also helps us predict what would happen if something is removed or added. If we were to remove the snake, well, that would hurt the kite. What if we added another competitor for the goat? If we add something else, that's eating the goat. Well, that would affect the lion and the jackal. Now, all these food webs are just trying to track the movement of energy through an ecosystem. But the reality is that there's also other things that we need to track through ecosystems that our life is dependent on. Energy is the big one, but water, carbon, nitrogen, and phosphorus. We don't really look at phosphorus, but it is true. are all different chemicals and molecules that we absolutely need for life and are not just available in unlimited supply there's a limited supply and life has to make sure it keeps recycling those nutrients through the life cycle so the water cycle is hopefully something you're familiar with all living things require water we have evaporation and transpiration right which is evaporation is water going into the air and transpiration is water going to the air from plants. That might be a new one for you. Basically, evaporation is just if liquid water turns into water vapor and goes into the air, and transpiration is basically if that happens from a plant. Then you have condensation, which is where water is going to leave the sky. It's going to condense and turn into liquid, and it'll be in the form of clouds. That's liquid water. and then once the water gets heavy enough it'll drop out the clouds as precipitation and once it goes into the soil it starts percolating into the soil it means it flows into the soil and it can run off through the soil to your oceans or rivers or wherever it is so here's basically just an overview of what that looks like okay so you can have evaporation and transpiration taking place where the water is leaving going to air it condenses from water vapor to liquid once it condenses and it's heavy enough it precipitates and it can run off back into water and this cycle keeps making sure that water is always available for living organisms. We also have the carbon cycle. Remember, carbon is in almost every single one of our molecules. Organic molecules have to have carbon in them. Most of the carbon is bound up in living organisms or in rocks or minerals that have to be broken down. But any carbon that's free has to be moved through the carbon cycle to make sure it's available for organisms. So here's an example of what that looks like. Carbon dioxide is pulled out of the air through photosynthesis to be used to create glucose. That glucose is put into use by the tree or is used by plants or animals. When we breathe out, or when the plants do their cellular respiration and create gas, they are going to send the CO2 back into the air. Or if we die, all those carbon and our molecules go into the ground and get decomposed. And eventually it's sent up back through the air through combustion. The nitrogen cycle is really important because nitrogen is a key part of our DNA. And it's really important in some very essential proteins too. Nitrogen, what's interesting about it is it's very abundant. There's a ton of nitrogen in the atmosphere. However, I can't just breathe in nitrogen and use it. Nitrogen has to actually be put into a very special chemical through bacteria that live next to plants. And the plants then get that. nitrogen from the bacteria and then I get the nitrogen from the plants. It's actually a very complex process and there's a lot of nitrogen in the air but it doesn't do anything good to me unless I actually grab it from the plants. So think right here, here's your amino acid, right, and so here's nitrogen that amino acid so we need nitrogen for all of our proteins and it's also essential in our DNA. So here's just a very simple nitrogen cycle. Most nitrogen's in the air and I can't do anything with it. But as the nitrogen gets close to the ground, there's organisms, bacteria in the ground, which can grab it and stick into a molecule which I can use. The plants say thank you very much and grab it from the bacteria. And I will get it when I eat the plants or when I eat an animal that has some nitrogen in it. I'll be able to steal the nitrogen from there. And if ever it leaves and goes back into the air, it has to be recaptured by the bacteria. Now here's the big takeaway with all these cycles. All these cycles are important because we would very quickly quickly run out of these elements and this energy if organisms just use them and stole them and hog them to themselves when they died because that all those resources are important we have to keep cycling them we have to keep moving around so that new organisms can take advantage of those nutrients that also means so those nutrients are limited nitrogen is limited carbons limited water is limited Energy is limited. So because of that, because all that's limited, those can limit how populations can grow and what can happen to populations. We call these limiting factors. Anything that limits or controls the size of a population is a limiting factor. Think back to evolution when we were talking about, like, there's certain population sizes that, you know, there's a certain point where you reach a population size and you can't support any more of that population in the area. right and so only the fittest survive that's going on here on a larger scale where across the whole globe you can only there's only so many resources and that's affecting a lot of local populations Resources are finite, that means limited. And so because of that, we have different factors which are limiting us. And those factors can be abiotic, like water, available water, available carbon, available nutrients. And they can also be biotic, right? They could be like the organisms that are predating, like our predators or affecting us in an area. For humans, it could be like the... The type of wasps, right, that are in an area, or the diseases that are in an area. Those can all be biotic factors, which can limit our population size. So, abiotic limiting factors. These are very popular things that can make it so population cannot get larger. Available energy. The temperature of an environment. If it's too cold, not many organisms are going to live there. The available water. All life needs water. If there's not a lot of water, there's not a lot of life. Think about deserts. Carbon dioxide. oxygen, soil, minerals, pH. All of these are things which can limit the ability of life to live in an area. Now living things can also limit the ability of life to live in an area. Here's an example, predators and prey. When you have the prey in an area, if there are not a lot of predators, the amount of prey in the area will increase. Well, as that happens, as the number of prey increase, you'll notice the number of predators increase. What's going on? Well, there's more prey, so it means it's easier to hunt. You get your food better, you start growing up larger, your population starts growing larger. Now, all of a sudden, you have more predators. What happens to the prey population? It starts to drop. Why is that? Well, because there's more predators available. You can have... the prey is going to be killed easier, so there's going to be less and less prey available. As that happens, the predators start dying because there's not enough prey. As the predators die, the prey population is going to increase. This right here, the presence of the predator, is a factor that's limiting the prey's population size. Think also about competition for available nutrients. Organisms are always struggling for the same resources. We struggle for the same food sources that many other animals struggle for. There we go. Let's pull a graph up. Here we go. So when you have available resources, some organisms might be better adapted. Some might be less adapted, right? And we're going to see that the organisms that are better adapted will actually be limiting the populations of those that are not adapted. So if you look over here in this graph on the side, here are two populations of deer in the same area. And you see one population of deer increases and the other decreases significantly. Why? Well, because the red line, the deer on the red line are better adapted to food in the area. The deer... on the blue line are going to be significantly impacted and their population is going to be limited by the available resources. Now the limiting resources aren't just the ones I listed. They are not just the abiotic factors I listed and the bioexamples I went over. It could be really anything that's affecting the population. So don't just stick your head where you're like, okay, these are the only limiting factors. Analyze the situation. Say what's happening. Why are they being held back? And that could be a limiting factor. Now, why are limiting factors important? Limiting factors determine how many organisms can live in the area. We call it the carrying capacity. The carrying capacity of a population or of an area is how many organisms can live in that. So if you have like wild dogs, if there's not a lot of available food, the carrying capacity for the wild dogs will be very low because there's not food. food available for them. If you look at this graph right here, what you're looking at is you're looking at the carrying capacity of population. When the organisms are first introduced, they increase steadily because there are a lot of available resources. There is nothing limiting them. As they reach the point where the environment's carrying capacity, that growth slows down because it solves them harder to get resources, resources aren't as available, whatever it is. And you'll have fluctuations along that line as time keeps going. As the population reaches a point where there's more available resources, they'll grow to pass their carrying capacity. That will cause them to hurt the population, cause them to starve, they'll drop. as they drop resources become more available and they'll grow. So carrying capacity is the total number of organisms of a species that can exist in an area because of the biotic or abiotic factors. Now all of this competition for resources and limited resources leads to ecological relationships. And these are the key to life. These are just... basically how we define relationships between organisms trying to survive in environments. And there's five key ones, and we're going to focus on four. There's mutualism, predation, parasitism, commensalism, and competition. And we won't really talk about competition, but just keep in mind that competition is when two organisms are competing for the same resource. The ones that are favored will do better. The ones that are not favored will do worse. So mutualism. All right, mutual means that they're both benefiting, and so we represent this positive-positive. If you're on a test, you can do right hand-left hand. If you look at the right hand, is that organism benefiting? If you look at their left hand, is that organism benefiting? So both species benefit from the relationship. And here you have two examples. You have the bee collecting nectar from the flower, and it's spreading pollen as it collects nectar. You have the clownfish living inside the anemone. but also attracting prey to the anemone. In a predator-prey, you have one organism benefiting the other organism dying. So in this case, you are actually destroying another organism. This interaction right here is both going to be hurting the prey population and as the prey population decreases, hurting the predator population. So in this case, when you're reading the example, you would go, Predator is positively affected because they're getting the food. Prey is negatively affected because they're dead. That's a predation. Now, it's very similar to parasitism. In parasitism, one organism is affecting the other one negatively, but you're usually trying not to kill the other organism. Because if you kill the other organism, it's going to usually kill you also or severely impact you also. So in the case of parasitism, you have to think the parasite is being favorably impacted, so that's thumb up. The host is being negatively impacted, so that's thumb down. But the parasite is not trying to kill the host. It's just trying to take advantage of it. So that's why we're parasitism. Difference between predation and parasitism. Predation, you're trying to kill the organism to take its nutrients. Parasitism, you're just trying to live and take advantage of the organism. Finally, you have commensalism. This is where one organism is benefiting and the other is really not helped or harmed either way. They really don't notice. The barnacles of the whale is a really good example of this. The whale doesn't notice. He's a big old whale. Barnacles don't really affect it. But the barnacles are thriving on this because they're constantly getting new resources and nutrients as the water flows over them. All right, so I'm going to give you a couple examples and you can try to decide for yourself what is going on, what type of relationship we're looking at. So a species of scorpion spread to other areas by concealing themselves under the wing covers of large beetles. The scorpions gain the advantage of being dispersed over white areas while being protected from the predators. The beetles are affected by the presence of the hitchhiker. So what relationship is this? Well, on my right hand, the scorpion's benefiting, so that's a thumb up. The beetle is unaffected, so I just keep my fist closed, and that means commensalism. Aphids, a defenseless insect, feed on plant sap. Sugars and water from the sap are excreted from the aphid's waste. Ants find a colony of aphids and milk the water plant sap from the aphids. In return, the aphids protect them. The ants protect the aphids from predators and parasites. So what is this? Well, on my right hand, ants are milking the plant sap from the aphids. So they're getting food. So that's a positive. Thumb up. On my left hand, the aphids are getting protected from predators by the ants. That's a thumb up. I have two thumbs up, which means mutualism. Lichen is made of an algae and fungi. The fungi provides water for the algae. The algae provides food for the fungi. What is this relationship? So the fungi provides water for the algae, so the algae is getting water. That's a thumb up for the algae on my right hand. On my left hand, the algae is giving food to the fungus. So that's on my left hand, a thumb up. I have two thumbs up. Mutualism. The cowbird lays their eggs in the nest of other bird species and rely on these hosts to incubate and raise their chicks. What is that? Well, the cowbirds lay their eggs in the other bird's nest and let the other bird do all the work. So the cowbird's benefiting. So that's a right-hand thumb up. On my left hand, I have the other birds. And the other birds are able to go through all the work. to take care of the baby. They're having to feed the cowbird's baby as well as their own. So that's a negative impact. That's thumb down. So I have cowbird thumb up, other bird thumb down. But the cowbird's not really trying to kill the other bird, just trying to take advantage of the other bird. So that means we are parasitism. Here's just some other examples of symbiotic relationships to look up. And we will end here for this unit. You should have your notes done and be ready to use them on centers and study them for tests and quizzes.

Now ecosystems are pushed very heavily in seventh and eighth grade in Florida so Hopefully this is something that you already have a very strong foundation of and will already know a lot about. And we can just build off, build on top of it for what we're learning for our class. All organisms on life or some are on the planet are in some way dependent on other organisms. We call this interdependence.

They could not exist without the presence of other organisms. Take humans for example, we have to get our oxygen from plants, we have to get our food from animals and plants, rely on animals and plants for our clothes. Every single thing that we do is reliant on other organisms. When scientists look at organisms, they actually classify all organisms into different levels.

Not just the classification that we learned about, but classification of what the organism's role is in life. And the lowest level of organization is going to be the organism or the individual. And when we get all the individuals that are like each other in a similar area, we're going to call that population. It's like all the humans in Jacksonville are the Jacksonville population. And then the community is going to be all of the organisms that exist.

inside a certain location that are regardless of whether they're the same organism or not, right? So like all the humans and all the dogs and all the cats and all the birds and all the mice and all the bugs inside Jacksonville would be the Jacksonville community. The ecosystem will be all the living and non-living things that are in Jacksonville. So that includes like the houses, the roads, and then if you take all of life.

that lives in the same area, like the same type of climate, the same type of weather conditions, that's going to be our biome. And finally, all life that exists on Earth is going to be the biosphere. And here's a summary of that. Now hopefully you should be aware that not all organisms in an area are the same.

In fact, there's lots of different variation of organisms in different areas. And this is referred to as biodiversity, which is basically the amount or number of different organisms in an area or in a location. And biodiversity is a very key thing because the more biodiversity there is usually, the more biodiversity there is.

The more interactions you have going between organisms and the more stable that community is, that ecosystem. If there's only a couple organisms in an ecosystem, you can knock one organism out and the ecosystem could struggle. But there's lots of different organisms in an ecosystem.

One or two organisms that are infected would not have a huge impact on the ecosystem. So in general, when you're talking about biodiversity, if you have more biodiversity, you're going to have a more stable ecosystem. So what are some things that could affect the ecosystem or can in some way impact either positively or negatively the biodiversity of an ecosystem? Well, first of all, we have what are called abiotic factors. A means not, and biotic, or bio, means life.

So these are factors, things that are not alive. So as the example shows, soil, pollution, natural disasters, climate, the type of minerals in a location. Anything that's not made of cells, that's going to affect the location. It's going to be an abiotic factor.

And then there's also biotic factors. What are the organisms that live there? If there are certain predators in the area, you will not have certain organisms. If there's... A certain competition will not have other types of organisms.

So these biotic and the abiotic factors are both going to have an impact on the ecosystem. So, look right here. What in this picture is going to be biotic and what will be abiotic? Well, what's made of cells? If you look at the plants, the phytoplankton, the fish and the turtle and the fungi, those are all made of cells.

Those are all going to be biotic factors. The water, the sun, the air, the sediment, those are all not made of cells. Those are going to be abiotic factors.

They all have an effect on that ecosystem. Now, the particular ecosystem in an area is going to be referred to as its habitat. This is a place where a particular population of organisms is going to reside.

And habitats are affected by both biotic and abiotic factors, and they can be very diverse and very specific to organisms. Here's just three other examples of your habitats. Now, when it comes to an ecosystem, an ecosystem is not just a whole bunch of animals and organisms that randomly happen to be living together.

Because it's interdependence, because every organism is in some way impacting another organism, the organisms and ecosystems are very specific. In fact, an ecosystem is usually a type of niche for specific organisms. And the reason this is the case, the reason that ecosystems are very specific about the organisms that are there and how they can survive and what they can do there, is because it's really all about energy.

Energy is a very valuable resource. Life cannot make its own energy. We have to steal it from the sun.

And so energy is very limited in reality when it comes to it being available, even though we don't really feel that because we always have lights on and we're always driving around. When it comes to the amount of available life on the planet, energy is a limited resource. And in fact, we're going to look at a couple other resources too, like carbon and water and oxygen.

And all of those things, if an organism were to use them and destroy them and make them not available for any other life, life would die very quickly on Earth. So instead of what life has done is it's adapted to where it's constantly moving energy and resources. and nutrients from organisms that don't need it anymore to organisms that do need it.

So as long as I'm alive, I'm going to be taking energy from plants. I'm going to be grabbing oxygen and carbon and nitrogen from different sources. But when I die and I don't need those anymore, the ecosystem is going to make sure that all those nutrients are taken from me and given to another organism that can use them.

So when it comes to the roles of animals and organisms in ecosystem. The reason they're so important, the reason they're so well defined, is because it's all about the energy flow in the ecosystem and conserving and preserving all the different nutrients available in ecosystems. So what are the different roles in ecosystems? Well, first, there's what are called producers. We call these things producers because they produce the energy that you and I can use.

They're autotrophs. They can make their own energy, and they use sunlight to make that chemical energy, the sugar. And then they use that sugar for all of life processes. And all of life is dependent on these producers.

Life could not exist without them. Next, you have a consumer. And consumers are heterotrophs. Hetero means other, and troph means energy. So we get our energy from others.

We cannot make energy from the sunlight, and we have to eat other organisms for energy and nutrients. Once again, though, that sugar, we have to use it for life processes. So we use sugar for the same reason that plants use sugar or producers use sugar. We use it for life processes. And producers, just so we're clear, like they're mostly plants, but you can also have bacteria that are producers.

Any organism that can do photosynthesis can be a producer. So some producers are also going to be producers. So the consumers, the organisms that eat other organisms, get energy from other organisms, they use that sugar for life processes. Now right here I have a photo of a pitcher plant, and this is a carnivorous plant.

This is a plant that eats animals. And what happens is you'll have a little animal climb up on the side like a rat, or sometimes even like a small monkey or a bug. And it will reach into the side, try to get something inside this pitcher, and it will fall down.

And the pitcher is strong enough to actually capture it. and make it so the organism can't get back out. And there's little digestive enzymes inside this plant, which will then start digesting the organism. Very gross, very painful, but that's what the plant does. Now, this plant's funny because when it's eating the organism, it is a consumer.

But at the same time, it can also do photosynthesis, so it can also be a producer. So depending on what role it is in the ecosystem, it can be both a producer or a consumer. But most organisms are either one or the other.

Now there's many different types of consumers. It's all based off your level in the ecosystem. So this right here is a special type of graph that shows us the role of different organisms in the ecosystem. Here's those producers we were talking about that capture sunlight and turn it into energy. If you're an organism that eats the producer, you are called a primary consumer.

Primary means one, so you're the first level consumer. If you're an organism that eats the first level consumer, you are a secondary consumer, right? Secondary refers to two or second. If you're an organism that eats the organism that eats the organism that eats the producer, you're a tertiary consumer and you can keep going up to quaternary, quaternary, sextonary, as far as you want. Most ecosystems, though, you really just go up to tertiary and quaternary consumers.

You don't really go much higher. Think about like... us and cows. A cow is a primary consumer and eats the primary producer, and we eat the cow, so we are secondary consumers when it comes to the cow.

But basically, consumers can have different levels, and the level is just determined by how far you are from the producer. If we eat lettuce, we are the primary consumer because we're eating the producer directly. Now, there's a third role in the ecosystem. These are heterotrophs. that are called decomposers.

So decomposers, they actually eat or decompose dead things. And once again, what are they using that sugar for? For life processes. So we all use sugar for the same thing, the same reason, we just get it from different sources. And these could be fungi, they could be bacteria, they could be any different types of other organisms.

But their job is to grab all those resources from dead organisms that the dead organisms are not using anymore. and use them for their life processes, and then put those resources, any spare resources, back into the soil, back into the circle of life. So these right here are really key.

Remember earlier I was talking about how we want to make sure our resources keep cycling and keep circling, that when I die, the resources don't just stay with me, that they actually move and aren't used by other organisms. One of the keys to that is the decomposers, because they get those dead organisms, and they make sure the nutrients that I no longer need, are being moved to organisms that can use those nutrients. Now, in order to track how these nutrients flow or move through an ecosystem, there are three different types of models that scientists use.

The first is called a food pyramid, and this shows a direct path of energy movement. So it says energy goes from the plant to the cow, to the fox, to the bear, right, or to the wolf, to the bear. from here to here. It never goes backwards, right? The bear doesn't get eaten by the fox, and the cow, the fox doesn't get eaten by the cow, and the cow doesn't get eaten by the grass, right?

It just goes one direction. If for some reason the bear does get eaten by the fox, then we switch their places. Now what's really interesting about energy pyramids is that there's this 10% rule, which is just generally true in science, which says that if grass makes all this energy from the sun, Only 10% of all the energy that the grass uses goes to the cow. So let's say right here that the grass makes 1,000 units of energy.

When the cows come and eat the grass, they're only collecting 10% of that available energy. So they're only collecting 100 units of energy. Where does the other 90% of energy go? Where are the other 900 units? Well, they're used for the life processes of...

the grass. The grass has to do its normal life processes. It has cells. It has to work through, it has to keep the cells alive.

They have to do their functions. And so most of the energy is going to be used for that. And only 10% is used by the cow. Now if you get all the energy the cow collects, and let's say it's 100 units of energy, when it's eaten by the wolf, only 10% of the available energy from the cow is used.

by the wolf or collected by the wolf why is that well that's because the cow uses a 90 for its life processes for its survival for its cells doing things and this goes up the list each time you move up there's a 10 reduction in the available energy and that's why like we have lots of grass and lots of primary consumers but if you look in like a a area any area you're gonna have very few secondary and tertiary consumers because Most of the energy that is required to sustain a tertiary consumer is lost as it goes up the cycle. Think about lions in the African pride lands. You don't have very many lions relative to the amounts of grass and gazelles and other animals because most of the energy is used by the grass.

And then most of that available energy is used by the gazelles when they eat the grass. And only a little bit of energy is available for the lions, so there are not very many lions. The food pyramid also shows really clear trophic levels and trophic levels are just the words that we use to represent the different labels for our consumers, our producers, and our decomposers. So the first trophic level right here is the producer and the first trophic level is always going to be your producer.

Second trophic level is going to be your primary consumer, third trophic will be your secondary consumer, fourth trophic will be your tertiary consumer, it's going to go up until this pyramid ends. Here's just another example of the energy pyramid. Here you have rainforest leaves.

And if you look, they collect 100% available energy. And the insect larvae come and eat the leaves. The insect larvae are only able to collect 10% of the energy from the leaf.

The bonobo comes along and eats those little insect larvae and only gets 10% of the energy from the insect larvae, which is only 1% of the energy from the leaves. And the bonobo actually gets eaten by the crocodile. The croc dot only gets 10% of the available energy from the bonobo, which is only 0.1% of the available energy from the rainforest leaves. Alright, our second type of model is called a food chain.

And this is, again, just a direct path of movement. It just shows energy goes from one thing to another, to another, to another. It's similar to a food pyramid, but it doesn't really show the amount of energy moving through the system. And it doesn't necessarily show the trophic levels, though it can. But it does tell us how energy is moving from one place to another.

When you're looking at this, energy always moves from the end of the arrow to the beginning. Okay, so where the arrow is pointing, that's where the energy is moving to. So the energy is moving from the producer to the grasshopper. The energy is moving from the grasshopper to the frog. And the energy is moving from the frog to the snake.

Okay, so this just shows where the energy is moving to. Our last type is a food web. And this shows...

all the possible passive energy movement in a system. Once again, the arrows show where the energy is moving. So the rabbit eats the leaf, so the energy is moving from the leaf to the rabbit. The wildcat eats the rabbit, so the energy is moving from the rabbit to the wildcat.

This also helps us predict what would happen if something is removed or added. If we were to remove the snake, well, that would hurt the kite. What if we added another competitor for the goat?

If we add something else, that's eating the goat. Well, that would affect the lion and the jackal. Now, all these food webs are just trying to track the movement of energy through an ecosystem.

But the reality is that there's also other things that we need to track through ecosystems that our life is dependent on. Energy is the big one, but water, carbon, nitrogen, and phosphorus. We don't really look at phosphorus, but it is true. are all different chemicals and molecules that we absolutely need for life and are not just available in unlimited supply there's a limited supply and life has to make sure it keeps recycling those nutrients through the life cycle so the water cycle is hopefully something you're familiar with all living things require water we have evaporation and transpiration right which is evaporation is water going into the air and transpiration is water going to the air from plants. That might be a new one for you.

Basically, evaporation is just if liquid water turns into water vapor and goes into the air, and transpiration is basically if that happens from a plant. Then you have condensation, which is where water is going to leave the sky. It's going to condense and turn into liquid, and it'll be in the form of clouds. That's liquid water. and then once the water gets heavy enough it'll drop out the clouds as precipitation and once it goes into the soil it starts percolating into the soil it means it flows into the soil and it can run off through the soil to your oceans or rivers or wherever it is so here's basically just an overview of what that looks like okay so you can have evaporation and transpiration taking place where the water is leaving going to air it condenses from water vapor to liquid once it condenses and it's heavy enough it precipitates and it can run off back into water and this cycle keeps making sure that water is always available for living organisms.

We also have the carbon cycle. Remember, carbon is in almost every single one of our molecules. Organic molecules have to have carbon in them.

Most of the carbon is bound up in living organisms or in rocks or minerals that have to be broken down. But any carbon that's free has to be moved through the carbon cycle to make sure it's available for organisms. So here's an example of what that looks like.

Carbon dioxide is pulled out of the air through photosynthesis to be used to create glucose. That glucose is put into use by the tree or is used by plants or animals. When we breathe out, or when the plants do their cellular respiration and create gas, they are going to send the CO2 back into the air.

Or if we die, all those carbon and our molecules go into the ground and get decomposed. And eventually it's sent up back through the air through combustion. The nitrogen cycle is really important because nitrogen is a key part of our DNA.

And it's really important in some very essential proteins too. Nitrogen, what's interesting about it is it's very abundant. There's a ton of nitrogen in the atmosphere.

However, I can't just breathe in nitrogen and use it. Nitrogen has to actually be put into a very special chemical through bacteria that live next to plants. And the plants then get that.

nitrogen from the bacteria and then I get the nitrogen from the plants. It's actually a very complex process and there's a lot of nitrogen in the air but it doesn't do anything good to me unless I actually grab it from the plants. So think right here, here's your amino acid, right, and so here's nitrogen that amino acid so we need nitrogen for all of our proteins and it's also essential in our DNA.

So here's just a very simple nitrogen cycle. Most nitrogen's in the air and I can't do anything with it. But as the nitrogen gets close to the ground, there's organisms, bacteria in the ground, which can grab it and stick into a molecule which I can use.

The plants say thank you very much and grab it from the bacteria. And I will get it when I eat the plants or when I eat an animal that has some nitrogen in it. I'll be able to steal the nitrogen from there.

And if ever it leaves and goes back into the air, it has to be recaptured by the bacteria. Now here's the big takeaway with all these cycles. All these cycles are important because we would very quickly quickly run out of these elements and this energy if organisms just use them and stole them and hog them to themselves when they died because that all those resources are important we have to keep cycling them we have to keep moving around so that new organisms can take advantage of those nutrients that also means so those nutrients are limited nitrogen is limited carbons limited water is limited Energy is limited. So because of that, because all that's limited, those can limit how populations can grow and what can happen to populations.

We call these limiting factors. Anything that limits or controls the size of a population is a limiting factor. Think back to evolution when we were talking about, like, there's certain population sizes that, you know, there's a certain point where you reach a population size and you can't support any more of that population in the area. right and so only the fittest survive that's going on here on a larger scale where across the whole globe you can only there's only so many resources and that's affecting a lot of local populations Resources are finite, that means limited. And so because of that, we have different factors which are limiting us.

And those factors can be abiotic, like water, available water, available carbon, available nutrients. And they can also be biotic, right? They could be like the organisms that are predating, like our predators or affecting us in an area. For humans, it could be like the...

The type of wasps, right, that are in an area, or the diseases that are in an area. Those can all be biotic factors, which can limit our population size. So, abiotic limiting factors.

These are very popular things that can make it so population cannot get larger. Available energy. The temperature of an environment.

If it's too cold, not many organisms are going to live there. The available water. All life needs water.

If there's not a lot of water, there's not a lot of life. Think about deserts. Carbon dioxide.

oxygen, soil, minerals, pH. All of these are things which can limit the ability of life to live in an area. Now living things can also limit the ability of life to live in an area. Here's an example, predators and prey.

When you have the prey in an area, if there are not a lot of predators, the amount of prey in the area will increase. Well, as that happens, as the number of prey increase, you'll notice the number of predators increase. What's going on?

Well, there's more prey, so it means it's easier to hunt. You get your food better, you start growing up larger, your population starts growing larger. Now, all of a sudden, you have more predators. What happens to the prey population?

It starts to drop. Why is that? Well, because there's more predators available. You can have... the prey is going to be killed easier, so there's going to be less and less prey available.

As that happens, the predators start dying because there's not enough prey. As the predators die, the prey population is going to increase. This right here, the presence of the predator, is a factor that's limiting the prey's population size. Think also about competition for available nutrients.

Organisms are always struggling for the same resources. We struggle for the same food sources that many other animals struggle for. There we go.

Let's pull a graph up. Here we go. So when you have available resources, some organisms might be better adapted. Some might be less adapted, right?

And we're going to see that the organisms that are better adapted will actually be limiting the populations of those that are not adapted. So if you look over here in this graph on the side, here are two populations of deer in the same area. And you see one population of deer increases and the other decreases significantly. Why? Well, because the red line, the deer on the red line are better adapted to food in the area.

The deer... on the blue line are going to be significantly impacted and their population is going to be limited by the available resources. Now the limiting resources aren't just the ones I listed. They are not just the abiotic factors I listed and the bioexamples I went over.

It could be really anything that's affecting the population. So don't just stick your head where you're like, okay, these are the only limiting factors. Analyze the situation. Say what's happening. Why are they being held back?

And that could be a limiting factor. Now, why are limiting factors important? Limiting factors determine how many organisms can live in the area.

We call it the carrying capacity. The carrying capacity of a population or of an area is how many organisms can live in that. So if you have like wild dogs, if there's not a lot of available food, the carrying capacity for the wild dogs will be very low because there's not food.

food available for them. If you look at this graph right here, what you're looking at is you're looking at the carrying capacity of population. When the organisms are first introduced, they increase steadily because there are a lot of available resources. There is nothing limiting them.

As they reach the point where the environment's carrying capacity, that growth slows down because it solves them harder to get resources, resources aren't as available, whatever it is. And you'll have fluctuations along that line as time keeps going. As the population reaches a point where there's more available resources, they'll grow to pass their carrying capacity.

That will cause them to hurt the population, cause them to starve, they'll drop. as they drop resources become more available and they'll grow. So carrying capacity is the total number of organisms of a species that can exist in an area because of the biotic or abiotic factors.

Now all of this competition for resources and limited resources leads to ecological relationships. And these are the key to life. These are just...

basically how we define relationships between organisms trying to survive in environments. And there's five key ones, and we're going to focus on four. There's mutualism, predation, parasitism, commensalism, and competition. And we won't really talk about competition, but just keep in mind that competition is when two organisms are competing for the same resource.

The ones that are favored will do better. The ones that are not favored will do worse. So mutualism. All right, mutual means that they're both benefiting, and so we represent this positive-positive.

If you're on a test, you can do right hand-left hand. If you look at the right hand, is that organism benefiting? If you look at their left hand, is that organism benefiting?

So both species benefit from the relationship. And here you have two examples. You have the bee collecting nectar from the flower, and it's spreading pollen as it collects nectar.

You have the clownfish living inside the anemone. but also attracting prey to the anemone. In a predator-prey, you have one organism benefiting the other organism dying. So in this case, you are actually destroying another organism. This interaction right here is both going to be hurting the prey population and as the prey population decreases, hurting the predator population.

So in this case, when you're reading the example, you would go, Predator is positively affected because they're getting the food. Prey is negatively affected because they're dead. That's a predation. Now, it's very similar to parasitism.

In parasitism, one organism is affecting the other one negatively, but you're usually trying not to kill the other organism. Because if you kill the other organism, it's going to usually kill you also or severely impact you also. So in the case of parasitism, you have to think the parasite is being favorably impacted, so that's thumb up. The host is being negatively impacted, so that's thumb down. But the parasite is not trying to kill the host.

It's just trying to take advantage of it. So that's why we're parasitism. Difference between predation and parasitism.

Predation, you're trying to kill the organism to take its nutrients. Parasitism, you're just trying to live and take advantage of the organism. Finally, you have commensalism.

This is where one organism is benefiting and the other is really not helped or harmed either way. They really don't notice. The barnacles of the whale is a really good example of this.

The whale doesn't notice. He's a big old whale. Barnacles don't really affect it. But the barnacles are thriving on this because they're constantly getting new resources and nutrients as the water flows over them.

All right, so I'm going to give you a couple examples and you can try to decide for yourself what is going on, what type of relationship we're looking at. So a species of scorpion spread to other areas by concealing themselves under the wing covers of large beetles. The scorpions gain the advantage of being dispersed over white areas while being protected from the predators.

The beetles are affected by the presence of the hitchhiker. So what relationship is this? Well, on my right hand, the scorpion's benefiting, so that's a thumb up. The beetle is unaffected, so I just keep my fist closed, and that means commensalism. Aphids, a defenseless insect, feed on plant sap.

Sugars and water from the sap are excreted from the aphid's waste. Ants find a colony of aphids and milk the water plant sap from the aphids. In return, the aphids protect them. The ants protect the aphids from predators and parasites.

So what is this? Well, on my right hand, ants are milking the plant sap from the aphids. So they're getting food. So that's a positive.

Thumb up. On my left hand, the aphids are getting protected from predators by the ants. That's a thumb up.

I have two thumbs up, which means mutualism. Lichen is made of an algae and fungi. The fungi provides water for the algae.

The algae provides food for the fungi. What is this relationship? So the fungi provides water for the algae, so the algae is getting water.

That's a thumb up for the algae on my right hand. On my left hand, the algae is giving food to the fungus. So that's on my left hand, a thumb up. I have two thumbs up.

Mutualism. The cowbird lays their eggs in the nest of other bird species and rely on these hosts to incubate and raise their chicks. What is that? Well, the cowbirds lay their eggs in the other bird's nest and let the other bird do all the work.

So the cowbird's benefiting. So that's a right-hand thumb up. On my left hand, I have the other birds. And the other birds are able to go through all the work. to take care of the baby.

They're having to feed the cowbird's baby as well as their own. So that's a negative impact. That's thumb down.

So I have cowbird thumb up, other bird thumb down. But the cowbird's not really trying to kill the other bird, just trying to take advantage of the other bird. So that means we are parasitism. Here's just some other examples of symbiotic relationships to look up. And we will end here for this unit.

You should have your notes done and be ready to use them on centers and study them for tests and quizzes.

Transcript for:Understanding Ecosystems and Interdependence

Transcript for:
Understanding Ecosystems and Interdependence