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Current time:0:00Total duration:10:26

Flow of energy and matter through ecosystems

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Video transcript

let's think a little bit how energy flows and how matter is recycled in an ecosystem and so the whole time that we go through this video think about these two ideas and then even after watching this video look at ecosystems around yourself even ones that you are part of and think about how energy flows and how matter is recycled so let's first think about energy so the energy for most ecosystems originally comes from the Sun there are other sources of energy you could think about even moonlight but that essentially comes from the Sun but there's also geothermal energy but the Sun is the source of most energy for most ecosystems we can think of and how does the ecosystem make use of that energy how does that get into how does it get stored within the ecosystem especially as biomass well it starts with primary producers which are usually going to be plants they can also be bacteria that are able to photosynthesize or that are able to take that energy and create biomolecules that store energy from it and so these are primary primary producers these plants in this diagram sometimes you'll see them referred to as autotrophs they are getting their own food from from the Sun from this energy and once again how is that energy stored well it's stored in these biological molecules if you were to zoom in into the molecules in this plant and this is a huge oversimplification you'll see all these bonds between these carbons and to make those bonds requires energy and if you were to break those bonds it could release energy and you might say well where did all these carbons come from that are in this tree well the carbon is coming from the air our air has carbon dioxide in it it has carbon dioxide so those are the carbons maybe let me draw some oxygens so two oxygens for every carbon and the whole process of photosynthesis is all about fixing that carbon let me write that word down we are fixing fixing that carbon in from a gaseous form when it's of carbon dioxide into the structure of the plant into into the biological molecules of the plant so it's storing that energy now it's not a perfectly efficient process not all of the energy from the Sun is going to be able to be stored some of it is being reflected even the plant itself as it as it goes as it lives as it reproduces as it cells divide some of that energy is used and eventually that energy is released as heat and you're going to see this trend a lot in thermodynamic systems that you are take you're going from one energy you're using energy to do some work but in the process you are going to be producing heat but this is just the beginning of our of our energy flow now we can think about how it that energy now flows to the other actors in the ecosystem so the next phase and this is a very simplified diagram or ecosystem that we're thinking about most ecosystems are far far far more complex let's think about the characters that would eat the plants the characters that would eat the primary producers and we call the folks that eat the primary producers we call them primary consumers so this bunny or this squirrel right over here they are primary primary consumers they consume the primary producers and why do they consume them why do why does a bunny eat the grass well because it gets energy from those bonds between in the biological molecules from those carbon bonds and and other bonds and it's able to use that energy to grow itself to reproduce to live to run around and it also stores some of that energy in its own biomass and once again this process is not very efficient going from one layer of trophy to another layer of trophy you only have about ten percent ten percent of the energy gets transferred or gets stored in the next gets stored in the next layer why only ten percent well because not all of the plants get eaten the whole process of eating plants digesting plants some the energy gets some of the energy gets pooped out gets pooped out because the the primary consumer here or the consumer isn't able to get all of it out of the actual biological molecules and so overall it's an inefficient process now we're not done yet we still have energy stored and the biological molecules of this primary consumer that someone might be interested in and we know that in many ecosystems there are things that like to eat rabbits or even squirrels and in this drawing it will be this fox and this fox because it eats primary consumers we would call it a secondary consumer a secondary consumer and you could keep going on with this if there was some character out here let's say there's some guy who likes to eat foxes that's a knife in his hand that he uses to go after the foxes with well so the Fox could go to him and once again why is he eating foxes well he wants that energy in that Fox and actually some of them is actually not just about molecules will talk about matter in a second he wants the energy and the matter from the Fox to grow and live himself and so this character would be called a tertiary consumer tertiary consumer and if there's no one who wants to eat him well then he would be considered a an apex consumer an apex predator and these characters that eat other animals we've talked about it before they're called carnival carnivores but let me just say he's the apex and apex we're really thinking about the top of the food chain that's why they're called that would be called an apex consumer or an apex predator but we're not done yet because at some point all of these characters whether we're talking about the trees the bunnies the Fox this this character who likes to eat foxes that they're going to die and that energy just doesn't disappear and in general you're going to see energy is conserved and it flows from one place to another that energy is then going to be used by it is going to be used by these characters right over here which we call decomposers they can take all that leftover energy in that that dead carcass or even in the poop and they can make use of it once again for them to live for them to reproduce and that and and then they by breaking that down they they can release a lot of those nutrients and the matter that's used and once again the matter is recycled once again to be used to be used by the plants so it creates this really nice cycle and the important thing to realize is it comes in as light that energy gets transferred as we go to through the layer different layers of trophy and and it's not a completely efficient process and a lot of that energy especially as we as these organisms live and reproduce and run around gets released as heat now we focus a lot on the energy let's think a little bit about the matter and I've already touched on it but the matter is recycled there isn't at least the way we've set this up there isn't a new matter that is entering or leaving these ecosystems or being magically created or magically destroyed as I mentioned when you look at a leaf on a on a plant growing or a tree growing or a leaf of grass growing that matter isn't just coming out of nowhere it's coming out of the it's it's just a different form or maybe the best way to put it that matter was always there in the form of carbon dioxide the plant is just using that energy from the Sun to fix that carbon from a gas form into into a solid form and it's able to use that energy to form bonds but bonds between the carbons in these biological molecules that actually store energy and the plant can use that energy to grow and as we've talked about things that eat the plants or things that eat the things that eat the plants can use that energy and as we talked before the carbon dioxide comes in these plants and maybe this this hour might be a little bit misleading so let me erase that let me erase that for now but we release oxygen o2 that oxygen and we've seen that as part of the photosynthesis process that oxygen is used by the animals to metabolize these biological molecules we study that in ecology in respiration and the matter itself as we say we have this carbon right over here when it gets eaten well then that becomes part of the biomolecules inside inside of this inside of this body and when the bunny uses those any of these biological molecules as a source of energy so it's able to break those bonds through respiration well then that carbon that carbon gets released in the form of carbon in the form of carbon dioxide so maybe this is a better way and actually it was already drawn right over here and so the important thing to realize is that energy is flowing light from the Sun comes in it's slow you know all this action goes on and then it gets released as heat as heat on almost every step but the matter itself it's always been there all of the atoms in our body on earth it's just constantly being recycled it's actually was generated inside of stars many many billions of years ago and we just keep reusing it over and over and over again it gets recycled from one form to another even after all of these these biological after these actors die the decomposers break them down into simple inorganic molecules as we talked about before that can then be used as the plants in conjunction with the carbon from the air and the light from the Sun and water that gets through its roots to start that process all over all over again
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