dude we made it we are on the last hacking unit of ap biology isn't that crazy it is finally time for the long-awaited unit 8 ecology it's going to be epic come on it's the last unit it can't not be evident hello everybody i'm kara and today we're just going to be going through all the stuff you gotta know for the last unit of ap biology and finally we are done with our theory a bunch of you guys come asking me to make this last one and finally i'm getting to it okay i'm sorry i couldn't make it earlier but we are here we are here alright so to begin our epic adventure into the land of ecology you first got to understand the way the world is organized right in a biological perspective of course who cares about the political organization of the world that is just wang so basically all our other units have been at the organismal level right oh my god that's a mouthful right basically an organism is a single dude like i'm an organism you're an organism my camera is sadly not an organism but you are don't worry now when you have a big group of a single species that is called a population so for example if you have a force and there's a bunch of rabs living in that forest and happily jumping around they are a population of rabbits they are a different population from a rabbit and like a different different forest somewhere else and then we have communities which are basically just a bunch of populations mashed together so if we had our population of rabbits and we combine it with a population of i don't know what else lived in forests dude rabbits even live in fort i don't even know but let's just say we combined it with like a population of quail or turkey or something then all the populations in that forest come together to form a community right so basically that's when like different animals different plants all the all the organisms in that like forests are interacting with each other that's a community now the way i like to remember the difference is like when you talk about your school right you're basically saying like all the students at your school is the population right but then when you say you're doing work in your community that could talk about your school that could talk about like your library that could talk about anything in that city right not just people who go to us that are part of a certain group so communities are just a bunch of organisms interacting with each other right then we add in all the like non-living stuff that they interact with right and we get an ecosystem like for example soil is not part of the community right because the community is only living stuff but then when you go to the ecosystem level you're basically including all the soil as well and of course the organisms interact with the non-living stuff right they're called abiotic factors they're not very relevant but basically the trees like grow and how well they grow depends on the soil they grow it and then finally all the ecosystems of planet earth come together to make your biosphere oh my god it's a sphere so it's probably the earth very nice all right so nice that's all you got to know about organization let us move on and we're going to go through each of these one by one it'll be epic so we've already talked a lot about organisms right like we don't want to keep like slapping a dead horse all right i don't know how the saying goes but we're going to talk more about animal behavior now right so we've talked about a lot about like animal physiology how they work and that kind of stuff now we're going to talk about their behavior right what they do for example me talking to a camera is a very awkward weird behavior but i'd still do it that's a behavior okay it has nothing to do with like how my heart pumps blood throughout my body okay it's something i choose to do and basically behaviors are done in response to your environment right you don't just like always talk to a camera that would be extremely weird well that's kind of a bad example but but like a better example is like when you burn yourself you draw your hand back right so the stimulus the thing that causes it is like hot stuff that you're touching stove stuff i don't even know yeah still okay and then your and then the behavior is what results from that right so stimulus causes behavior sorry not behavior action and then this whole flow chart is a behavior all right so now that we have the concept of behavior we actually have to know why right like what's the relevance of behaviors why the heck do we care about all this nonsense about animals doing random stuff well basically the dude named tim bergen basically he's some random ornithologist who cares where he came from but what we do care about are the four questions that he posed about behaviors first what causes the behavior right that's just like what's the stimulus right all right how does it develop like for example is it something that i don't know how to do instinctively right like or is it something that i learned over time like touching a stub reflex it's obviously not something you learn right you don't like the first time you try to sell you're not like oh yes it feels so good and then you slowly take it off right no that's like something that's you know right off the bat you just automatically do it because it hurts so those are called innate behaviors right stuff that you already have and then of course there are learned behaviors right like for example i learned how to use photoshop yeah that's that's a good example like a baby did not know how to use photoshop but i am clearly a master you can see how good my my handwriting is epic all right and then third we have how does it affect fitness right like there's no reason why somebody would evolve a behavior if it doesn't like make make them like more likely to survive i don't know why i play video games so much then if that's the case but but the point is how does it affect fitness okay well to be fair it's okay if it negatively attacks fitness okay like for example a behavior where like a chimp teaches her kids not to eat poisonous fruit that's clearly like going to increase your fitness right because eating poisonous fruit is like the stupidest thing you can do and that's obviously bad for your fitness so teaching so teaching your kids is obviously going to increase your fitness and then once we answer how it increases fitness then we could answer how did it evolve right like the chimps that teach their kids not to eat point in the fruits are gonna have more kids and their kids are probably gonna teach their kids right so that's how probably how that behavior evolved all right so these are the four questions we've got to keep in mind so let's move on these are pretty self-explanatory honestly i didn't really need to explain to you guys you guys probably already knew this stuff but this is gonna have it in your mind before we get into fun stuff so basically the first question is what caused it right so let's just talk about environmental cues right a lot of animals do stuff in response to the environment and basically the three examples that i'm going to talk about are migration hibernation and estimation and um most of these probably are familiar to you activation is like a weird one you probably don't know that one but migration right just moving from one place to another and this is obviously in response to like colder weather right like some birds could move north in order to avoid like super bad winters right then hibernation a bunch of animals like speed through the winter so they don't waste energy and that's basically triggered by decreasing temperatures right and then estimation the weird one that you never hear about but basically they sleep through summers right like if you're in a desert and it's a really dry environment and it gets really really bad in summer you probably want to sleep through the summer okay i'm not gonna lie i would want to sleep through all the bad stuff that happens to me but sadly it just doesn't work for some reason my mom was yelling at me and i tried to go to sleep but didn't work she didn't stop so sad now you don't really have to know much about these to know that they exist like these are pretty common english words so you should probably know that before you go to the test but it's not it's not particularly complicated or anything however a more complicated one that is actually pretty important are circadian rhythms and it sounds really fancy okay it sounds like well that's going to be super super complicated we're going to have to do with cicadas but no it's literally just rhythms right your daily rhythm of your body like basically the reason why you feel sleepy in the night is because due to these circadian rhythms that like change over the day your body starts secreting melatonin in the night right don't get it confused with melanin that's what makes my skin so dark okay but basically in response to the sunlight your body like undergoes changes throughout the day in this 24-hour cycle and that's just what a circadian rhythm is 24-hour changes in your body like honestly the only thing you get to know about circadian rhythms are is that their rhythms and they happen every day right don't don't worry about anything other like complicated stuff about them all you have to know is that they're daily cycles okay so now let us talk about the second question how is it learned and we already talked about two of the main times where you got the neighbors to learn so let's start with the nate why not so we already talked about one right reflexes that's pretty obvious right like that's just stuff that automatically happens when you touch a burning stuff when you step on it like tack your um foot push it up when you hit your when you hit your knee your your thing kicks that's why all the doctors have that epic rubber hammer dude i've never actually has it i don't even know the last time i've done a knee jerk reflex test but the actual reason why your feet do that like why when a like doctor hits that ligament it like kicks out it's actually kind of interesting it basically has to do with like lifting too much weight and if it feels so much strain there it basically causes you to stand up and then the other one that nobody knows about because like nobody like talks about this much for humans are fixed action patterns like they literally say right fixed action patterns like when an organism sees a certain stimulus it goes through this pattern exactly like every time you see that stimulus right fixed action pattern like in a response to something it always does the same thing and the stimulus that cause it is called the key stimulus not very relevant but it's fun to know so basically a very good example of this are sticklebacks right this is a very good stickle this is a very good stickleback drawing okay and you got a tail okay so essentially every time a stickleback sees another male stickleback right and that's also a sticklebacker promise and basically all these males have like a red belly very cool every time it sees another male stickleback it starts acting really aggressive right because basically these male sticklebacks fight each other for me but basically what scientists found out is that like even if they're no other male sticklebacks if you just show them something with a red belly they'll actually start acting aggressive two words so you could put a perfectly harmless like square blob and epic my drawing skills make it even more blobbyish and then you just put a red belly on it and even though it's not fish it doesn't even look like a fish the the male stickler that still attacks it and gets really angry and stuff and then when you put a lifelike model like you make it actually look like a fish but you take off the red belly the fish doesn't do anything it's crazy so basically all you have to know about fixed action patterns is that they happen in response to a very specific stimulus and no matter like what shape that stimulus happens in it always goes through the same action and it's innate okay you don't have to learn it like any stickleback would do well any male sticklebacks that like carry them at red things but but you get what i mean okay all right so what's the opposite of an eight yeah you guys remember that's right you guys were paying attention when i talked about it right right you better have been learned behaviors so basically there's a bunch of types of this but we're gonna start with habituation okay and honestly not very complicated right have it just means you got used to something you just do it over and over again and basically habituation all that means is that like something happens so often that you stop responding to it like if i keep clapping like this and it gets annoying after some time you just start ignoring it okay you might start yelling at me but like eventually you give up because i just don't stop clapping i guess i just did but basically your brain eventually tunes that out and that's habituation when you have a repeated stimulus it eventually stops mattering as much your brain tunes it out and that's habituation and it kind of makes sense why animals do that right because if you're constantly seeing something there's no reason why you should have to keep reprocessing it every single second so it makes sense from an evolutionary perspective and then the next one is imprinting now this one's the most confusing one like there's like no way to remember this because imprinting does remind me of like printing presses like what does this have to do with printing presses they're not making any newspapers here it turns out that imprinting all it means is that when like baby chicks hatch right that's a chick i promise oh my god that what is that oh my god oh you know i should stop trying to draw on these videos god dang it but yeah basically is when a chick that's all oh my god you know look at the percent of the chick oh yeah that's beautiful basically the chick when it hatches out of its shell it looks at the first animal it sees right which is usually his mother and it starts falling around the mother and doing everything that the mother does so that's basically imprinting basically when a chick like latches on to an individual and starts learning from them like at an early stage in their life and then you got your mama's nonsense thing yeah there you go it's bigger if it looks the same it's fine but the reason why this is relevant right is because once a baby gets out of his like egg right it's susceptible to predators and the best way to avoid the predators is to follow your mom around copy what your mom's doing if you get separated from your mom you're basically dead but another fun fact about imprinting is that like it could sometimes backfire right like um they're they're trying to like rehabilitate whooping cranes right and if the whooping cranes see a human first they only respond to the humans so basically the humans dress up in crane costumes to make sure that the like the birds still recognize what one of their own kind looks like it's crazy okay all right and now it is time for the fun stuff okay the stuff that annoys the heck out of people whenever they hear it conditioning all right i know this term from badminton because it sucks i i hate getting buff i mean i could use a little bit of that now god dang it but this is the ecology kind of conditioning okay so not that bad oh that's pretty bad you'll see it you'll see it so the first type is classical conditioning and honestly i don't know what's so classical about it because the other type is a bit more classical to me but all it means is that these two are like types of associative learning right and classical is basically associating something with something completely unrelated right for example if a dog why do i try to do this to myself oh my god that's an i don't know what that is that looks like a banana dude i don't know what's going on with my drawing so please ignore that but let's just say there's a dog and there's some food right and every time you give the dog the food you also ring a belt so obviously the dog salivates out the food right when you put the two together the dog is still gonna salivate at the food but eventually if you do that enough times the dog will also salivate at the belt so even though the belt is completely unrelated the dog learns to associate the the food with the bell and that like ultimately results in an action that is related to the food even though it's not related to the belt essentially all three together is conditioning it and then eventually either of them if you put the food only or if you put only the bell the dog will still have the same response now the other one makes a lot more sense to me operant right you're operating you're doing something to like achieve a certain goal right operant operational i don't know that's how i remember it but essentially it's positive or negative reinforcement right that's that's like what i think of whenever i think of conditioning which is why i thought it would make sense more to call this classical the opera makes a lot of sense right you're really teaching an organism how to do something by giving a positive or negative reinforcement so an example that a lot of books use is you have a rat and basically there's a lever and every time the mouse press the lever the food comes out right so essentially even if the mouse originally just hit the lever by accident it's going to be like oh there's food so maybe i should keep doing that and every time it gets more food the action is more conditioned and eventually it'll be like okay i should i know that every time i'm going to hit this lever is beneficial to me so it'll keep doing that but it can also go the other way right negative reinforcement if you hit the lever you get electric shock and eventually the my mouse will stop touching the lever alright now the next thing we want to talk about is communication and honestly there's literally not much in the book about communication and like i don't know why there's a whole subsection of the ap curriculum dedicated to communication but like most of the stuff you have to know is pretty self-explanatory right like basically animals could communicate with each other audibly right like i'm talking to you guys visually right i'm also like showing you guys stuff on the screen or they can also communicate with chemicals right and unfortunately i'm not sending you guys any chemicals to your house that would be kind of creepy but like for example dogs dogs is a pretty good example um they basically pee on everything if you're gonna have a dog you probably know that your dog pees on everything and that's because of something called pheromones so basically pheromones are just chemicals that are used to communicate with other members of your species right so when a dog pees on a i don't want to draw this too graphically but let's just pretend you know uh that's a tail that's a other leg and that is your raised leg for your dog and then it goes like that and oh beautiful i even got the splash marks so essentially every time a dog pees on something it leaves behind a bunch of chemicals that other dogs could smell and then there's also like coloration right like for example if a bee a bee has a yellow and white stripe because that tells other animals that bees are dangerous right that's also why like poison dart frogs all look like black and this really bright color so that's called episomatic coloring or just warning coloring and they're not really that relevant but the idea is that like animals could also communicate with other species just by how they look this is also an example of malaria mimicry right so basically two dangerous animals mimic each other so that people will learn to avoid them you know while i'm at it i might as well tell you guys about a petition memory creed right so malaria is basically like um warning dudes the reason why i remember that is because the mother sounds like such a like scary name i don't know it just sounds like robert mueller like special counsel seems like buff guy who's going to beat people up but bethesian just sounds like some random math guy he can't beat anybody up so petition are like not not strong guys pretending to be like big strong guys so that people don't attack them okay very epic with that out of the way let us now talk about something completely unrelated but still related to organisms we are going to talk about endotherms versus ectotherms i had no idea how to segue into this so we're just gonna go with it so whenever you look at fancy by words you just look at the latin roots because usually by words even though they suck i will admit that they usually are pretty descriptive so endo means in right and therms means temperature so these basically are the guys who generate their own temperature internally warm bloody guys and then exotherm ecto means outside their means temperature so you're getting your heat from the outdoors right so that's basically cold blooded so now the main difference that we want to talk about between endotherms and ectotherms are like their metabolic rate right because like obviously endotherms have to spend so much more energy keeping themselves warm than ectotherms essentially we could talk about bmr which is called basal metabolic rate and we could talk about smr which is standard metabolic and basically the reason why there's different things for endotherms and ectotherms is because endotherms like if you if you have the right temperature their energy consumption stays relatively the same right because they're always generating heat but ectotherms on the other hand it depends what temperature they're at right because if they're super cold they do have to like generate a little bit of heat like by shivering or they had to move around to get heat so essentially like smr depends on temperature which is why it's different from bmr like a single snake could have like a bunch of different smrs based on like what temperature did but bmr is constant so we already talked about how endothermic need a lot more energy right more energy so your bmr is generally going to be way higher than your smr's however a benefit of being an endotherm also means that you could go anywhere right like like endotherms could move around anywhere they want even if it's cold and they could still like move around fine and they could still survive pretty well but ectotherms when it gets cold they move really really slowly right because their metabolic rate just can't sustain movement and like like surviving the heat but also ectoderms like because they can't regulate the temperature they're also like they could survive bigger shifts in their temperature right because obviously if you can't regulate your temperature if you die every time your temperature changes you're just going to die immediately can live with different body temperatures alright so then another thing that's relevant to these guys is how body size matters right so you think that as your animal gets bigger you would need more energy to sustain it right well it turns out that it's the opposite well not really but like essentially the amount of energy you need per gram actually decreases as you get bigger like for example a mouth requires so much more energy than an elephant per gram to survive now honestly you don't have to know too much about it like all you got to know is that just smaller animals move around more like they they need like a lot more energy per gram and then obviously bigger animals are a bit more sluggish they don't need like as much energy per gram of body mass way more energy way more alright so now let's go back to warming stuff up and talk about how endotherms and ectotherms warm themselves up so for endotherms right like when you're cold you do not like go like out in the sun and sunbathe right to raid your temperature up right your your body automatically starts shivering it starts like doing all these things to regulate your temperature so one way they do it is something called thermogenesis right like you know that your computer gets pretty hot when it has to do a lot of stuff right so the same thing happens in your body when your body does a lot of stuff it generates a lot of heat so essentially thermogenesis is when your body generates heat by doing stuff for example shivering is an example of thermogenesis right you start moving your muscles really like really fast right and that warms you up because you're using more atp then also there is like something called brown fat which is basically just like it runs cellular respiration without generating any atp so it just keeps going it only generates heat brown fat and this is basically used by hibernating animals now you can also change how much energy you share with the environment right and this is a pretty common misconception that like sweat is water and that's why it cools it down just because of the fact that it's liquid but the actual reason why sweat actually cools you down is because the water droplets on your skin actually the heart the hottest part of the water droplets evaporates right and then it leaves behind cooler sweat so eventually if you're in a hot environment the evaporating sweat actually takes heat away from your body there's also a vasoconstriction flash dilation and basically this basically just means making your veins bigger or smaller right and essentially like heat enters and leaves your blood through your veins right or through your capillaries so for example in rabbit ears you probably could see their veins in their ears right and essentially on a hot day if they're if they're feeling cold and it's like hot and then they could dilate the blood vessels in their ears and more heat will enter their blood and they'll warm them up or if they're getting too hot and the environment is really really hot and they want to stop like taking in heat from the environment they can also do vassal constriction which means they make it smaller which means less heat is exchanged and then of course there is counter current heat exchange now this one is pretty complicated like honestly speaking you don't have to understand it that well but i'll just explain it i'll just do my best to explain it and you guys don't worry if you don't understand it too much but basically let's say say you have like something that's flowing from top to bottom and something that's flowing bottom to top right counter card let's say this part of the thing is like really hot right and it's getting slowly cooler so you guys know that like hot stuff goes to cold stuff right so if this part is colder then this will start like sending heat over right and then it'll start sending heat over all over here but what's cool is that this moving down actually like moves all that like like hot stuff out of the way so this part stays cold relative to this and this keeps moving the hot stuff up so there'll always be cold stuff to move the hot heat into on the left side but the one thing you should understand from this is that like having this setup maximizes the amount of heat that is transferred from this fluid to this fluid and basically animals use that like in dolphin flippers or duck feet they basically use counter current exchange to either maximize how much heat they're sharing with their environment or to minimize the amount of heat that they're sharing with their environment so ectotherms could do some of those things but one thing that they do that like most endotherms do or don't do is behavioral thermogenesis and basically all this means is that they just go on a rock and chill like this even though they don't get like a sexy tan they still do sunbathing okay but basically because their metabolism can't like heat them up they basically need the sun or like they had to move to different places to heat themselves up which is why it's called behavioral right they change their behavior in order to change the temperature dude this chapter is a bunch of random stuff i'm not gonna lie okay moving on though we are finally done with endotherms and ectotherms all right the next thing we're gonna talk about is life history right so basically how animals choose to reproduce now this is actually kind of a complicated question right like there's no clear answer on what the best way to reproduce is right although most people would argue that the more the merrier why not but some people would also disagree because basically there are a bunch of trade-offs to consider right for example um how many offsprings actually is a pretty big trade-off to consider because the more offspring you have the less you could put time into each one of them so basically some animals choose to have like a ton of offspring and just hope that some of them survive right like sea urchins have millions of eggs and only like a tiny fraction of them survive but like still enough survive that you still pass on your genes now if a human did that if a human had a million babies and hope that some of them survived that would be very sad and they'd probably get arrested or something i don't even know how that would work but you could probably see that like sea urchin they just throw their eggs into the open right humans do not throw their babies down into the open okay well hopefully they're not supposed to so basically like if you have more offspring you care you care for each of them less but if you have only a few offspring you care for them a lot more so there's a lot more parental care and then another one to consider is like earlier or later right if you have offspring early right then you're losing out on potential time you could have been growing right because reproducing takes a lot of energy right you're literally treating a new body inside of your own body so if you have your offspring too early it might be better right because you have less chance to get eaten by a predator but it's also kind of bad right because like you're you're basically crippled for the rest of your life so basically what some animals do is they wait for later to reproduce so that they could get bigger and be more able to protect their young and then they then then they reproduce and then finally there is the concept of semi-parody or eternal parody and basically the difference between the two is basically do you reproduce once or do you reproduce many times so basically for style purity you basically reproduce once and then you die it doesn't seem that fun but basically a bunch of like flies a bunch of like tapeworms and that kind of stuff they basically produce a ton of offspring once they just go one big boom and then they all die other animals like mammals for example they basically go through a bunch of cycles right menstrual cycles estrous cycles they basically go through these cycles and each time they produce offspring and it kind of makes sense right semmle means like one time right same one one one time and then itero means you're doing it iteratively right you just keep going one two three four five you keep going so speaking of reproduction why don't we talk about how like populations grow let's just say so basically there are two types of main growths for populations right there's exponential and there is logistic so exponential kind of makes sense right if each person is having offspring right the more people you have the more offspring you're gonna have right so essentially the more people you have the faster you grow which is why like if you have you start off slow and then as you get more people it just keeps going up right that's exponential now the the formal way to write this is like dn over dt is equal to rn not only does it look like fancy random calculus but it's actually pretty self-explanatory okay it's just the change in population size is proportional to the population size right the more population you get the more offspring are being produced and that's why it's like goes up really really steep because you're keep getting more and more steep and this makes sense right if you have no like restrictions on how much you grow right like obviously this makes sense but that's not true right like obviously i can't just grow as big as this room and feel it oh i mean i probably can't just because i can't but like if i were to keep growing okay then eventually i'd hit the roof and that would prevent me from growing right in the same way populations hit a so-called roof called the carrying capacity right so essentially every ecosystem only has so many resources right so like only so many people could survive after so many resources so instead of going like this and going really really steep it actually kind of looks something like this where it's like a s shape logistic has an s in it that is why it looks like an s makes very much sense but basically the reason for this is as there becomes less resources less people could actually have offspring and this is basically whenever a ecosystem could only support so many people of a population now the mathy way to put it if dn over dt is equal to like um n times k minus n over k which kind of makes sense right when n equals k this is zero which means that you stop growing and when you're at zero people how do you have offspring with zero people right so that also stops growing which is why it's like flat here and then eventually it maxed out here and it goes like that so so this makes sense and there's like some constant before a but that doesn't really matter okay just remember that logistic is an s-shaped curve when you have stuff like stopping them from reproducing and exponential is just this massive like upward thing just because there's no limits on it like you kind of see it right the beginning of logistic actually looks like exponential right because when you're far away from carrying capacity it doesn't really affect you all right so let's talk about the factors that cause this logistic growth nonsense they're basically divided up into things called density dependent and density independent factors now density dependent means exactly what it seems like in beans what do you guys think it means density dependent it depends on density holy moly that is crazy well basically to give you guys some concrete examples right as you get more and more people like in a certain place more of them are going to compete against each other right so competition is an example of a density dependent factor also if you get more crowded people disease is more likely to spread right and that's going to limit your population because like obviously people are more likely to die out if you're more dense there's a lot more examples but you guys basically get the idea right like if the damage something does is dependent on how many people there are then it is density dependent but if it doesn't depend on how many people there are then it's density independent right like a flood or a like fire right these guys don't even care how many people there are right they'll just kill whoever's in the way so for this one for identity independent basically all the examples are natural disasters right so if it asks is this thing a density independent or density dependent if it's a natural disaster go to the right if it's not just go to the left okay don't think about it too much well you probably should think about it a little bit but in most cases it's going to be left if it's not a natural disaster okay nice and now there is one more thing that we didn't talk about we talked about logistic we talked about exponential but things could actually go up and down and up and down right they're not just like these flat lines like say for example if we had a like predator right like let's say the links and we had a prey they're like hair or something so let's say the link's red it goes up and down you guys gotta admit that is beautiful and let's say the hair is blue so basically let's think about this right when there's not many links right the the um population of the rabbits is going to go up right but then as there's so many rabbits and so few links is the lynxes are going to increase in population right because there's so many rabbits and not that many links is to compete against each other well usually the rabbits are way above because there's way more prey than predator and then once there becomes so many links then the rabbits start going down right because there's so many predators so eventually it'll start going down but then eventually the hairs will start being too little to support all these lenses right and then the links will go down right so essentially these guys keep like going up and down together right well i mean technically if i drew this more carefully it'd be something like this something like that but yeah basically you see right like if there's a ton of links is it'll cause the hairs to go down but as the hairs go down then the links go down too and then it keeps going up and down with each other so that's just something to keep in mind that not everything is exponential or logistic okay we're almost done with population stuff okay so the next thing we gotta talk about are food webs okay we should probably black alright so you guys probably know that all food webs start at the very bottom right with people who could produce their own food and those guys are called autotrophs or producers right like obviously they're producing the food come on what else are you going to call them and otto means like themselves right they're producing their own food so that's why it's an autotroph so examples of these are plants right you don't see plants going around eating anyone unless they're vegan's flytrap and these guys are called photo autotrophs right because they basically turn sunlight into sugars and then the animals could eat the plants to get those sugars then there are also chemoautotrophs and these guys are less common you guys probably don't see them very often but basically these guys are the ones that use chemical compounds and the reason why you don't see them is because they're found very deep underwater in those like hydrothermal vents and they basically use the heat of the hydrodrum events along with like like um chemical compounds to make sugar and basically these autotrophs are eaten by heterotrophs right like hetero means different right so they're getting their food from a different animal and they're called consumers because they consume stuff holy moly is crazy and these could be anything right like a rabbit is a consumer a fox is also a consumer even though it doesn't directly eat the plants it eats a rabbit but it's still called the consumer so essentially we could draw this from top to bottom or left to right well top to bottom probably makes more sense so essentially you have your um like i don't know grass which is eaten by the rabbit which is eaten by the fox which perhaps is eaten by a bear who knows probably not but let's just say that for for argument's sake okay so essentially these guys are the producers right primary producer this guy is a primary consumer right because it's the first consumer in the chain basically chain is when you have one to one to one to one food web is when you have a bunch of chains combined in all random ways but this is just one chain primary consumer then it fox guess what it is if the rabbit is primary what do you think the fox is that right is secondary consumer and finally we have tertiary consumers or if they are not eaten by anyone they're called apex predators now each of these levels is called a trophic level okay so i don't know how to remember that well but basically all these things are called traffic level primary produces a traffic level right all the primary producers combined make one traffic level then you go up one you get to the primary consumers then you go up one you get to the secondary consumers and then you go up one and you get the tertiary consumer now the reason why this is relevant is because all the energy started from here and it has to go through each of the tropic levels to eventually reach the top tropic level right and as you gotta know nature is pretty inefficient okay like maybe not after an efficient and your dad's like 2001 like honda odyssey bro that's only why i have to drive to school every day it's kind of embarrassing but it's still pretty inefficient so so if there's like a ton of energy in the grass only 10 of that energy in the grass is actually converted to the rabbit energy right so while these rabbits are spoiled on like heaps of grass the foxes only have ten percent of that energy to have their fun on and then the foxes only gain one percent of the ten percent of the energy of the grass so overall they only get one percent of their original energy because like every traffic level only ten percent goes up right so ten percent of 10 is only one percent so basically even the foxes are kind of spoiled okay the bears are the ones who actually are living in tough and they only get 0.1 percent of the energy of the grass so you can probably see right why there's so much grass there's a lot of rabbits not quite as much rabbits as there is grass and then there's even less boxes and then they're very very very few bears right because essentially there's very very little energy available to those bears and then of course like outside of these food chains are things that like when any of these guys die right there basically has to be somebody who decomposes them right and they get all the energy of the universe they just get whatever dies so they don't they're pretty spoiled too and these guys are like fungi and bacteria and stuff now very fun fact that a lot of people mess up decomposer means that they actually secrete chemicals that break down molecules into their very very like basic form right but there are things called the tridivores like vultures and stuff they eat dead stuff too right but they don't actually like break it down to the individual molecules like the fungi and bacteria do right fungi bacteria secrete these chemicals and break them down in the environment water is actually ingested and then break it down so that's the main difference the trident where the ingested decomposers actually break it down in the environment so why don't we actually like think about a very fun like thought experiment because i like sounding like einstein even though i'm not so we start with our p1s our primary producers then we go to our primary consumers c1 and then we go to c3 or c2 one two three very epic c3 okay so let's think what happens if we increase the number of p1 right well if there's more grass right there are going to be more rabbits because the rabbits have more grass to eat then if there's more rabbits to eat then there's more foxes and then if there's more foxes to eat and then more bears right so essentially all of these guys go up if this guy goes up then all these guys will also go up and then obviously if we decrease the amount of grass they're going to be less rabbits they're going to be less boxes and there's going to be less bears but what happens if we for example decrease the number of bears then there's less bears to eat boxes right so that's probably going to go up then if there's more foxes to eat the rabbits then they're probably going to be less rabbits and if there's less rabbits to eat the grass then there's going to be more grass so it's kind of cool right if you go from the bottom up it actually increases everything but if you decrease the number of predators it actually alternates it goes down it goes up it goes down it goes up so whenever you're doing these kind of problems i'm pretty sure they will ask this kind of thing on the test but essentially the idea is when something goes down the thing under it will go up but if something goes up then the thing above it will also go up and this makes sense logically right if you have more things to eat something the thing that's getting eaten will go down if you have less thing to eat something the thing that is getting eaten will go up okay epic we are almost done we are finally on communities okay and remember communities are when you have a bunch of populations of the same species interacting with other species so because there's a bunch of species interacting we got to talk about inter-specific interactions which means between species interactions which is basically what i've been saying this whole time and basically in these interactions there's two species involved right and essentially either one of them can benefit or not benefit so then we need to represent these interactions we just use a plus slash plus or like plus slash minus but i can speak but basically like what like this means that one benefits one like uh is harmed this means both benefit like obviously minus minus would mean both like are get harmed by the interaction and so on and so forth so why don't we get started with all of the interactions all right first you got competition and that basically means two species are trying to do something or like sharing a certain resource and they both need to like are both are trying their best together and this if you think about it is minus minus right like both species like would do better if there was not another species to compete against it then there's predation right like obviously for this one like one of them is benefiting right one of them gets a very epic like five star meal and the other one gets dead so it's quite really a minus okay then there's like a whole another category called symbiosis and that basically is when there's a really close relationship and this could fall under three categories that you probably know already mutualism immediately makes sense right mutual means it's both ways so mutualism means that both of them benefit commensalism is a wack one that you probably will not remember compared to the other two because mutualism's pretty obvious commensalism is just plus slash zero right one of them benefits the other one is not harmed and this is parasitism which you guys probably already know like obviously one thing is benefiting by riding on a host and then the host is losing out so it is plus slash minus all right nice so basically these ones are pretty straightforward right like mutualism is when clownfish and an anemone right like both the anemone and clam fish benefit from their interaction commensalism like they're not that many uh inter like interactions that are commensalism because like usually they're gonna have some impact on each other then parasitism there's a lot of impact like a lot of examples right like um like any tapeworm in a human is like parasitism right because it causes disorders in the humans but the tapeworms actually get to reproduce wow what a good deal but the more fun one is competition so let us talk about competition so then the competition is just species like competing for resources right and essentially each like each species has something called a niche and that basically talks about which resources those are describes resources used by organism now basically why this is relevant to competition is because if niches overlap right if multiple organisms are using the same resource then there's going to be more competition between them more overlap equals more competition like if you and your friend both have the same hobbies right you guys are going to be fighting against each other to be better at one of the all of those hobbies all the time right but when it comes to species it's a little bit more cutthroat than that because it turns out that there's something called the competitive exclusion principle which is pretty descriptive actually and it basically says that no two animals can have the same niche right because if two species are have the exact same niche one of them is going to be slightly better right so eventually the one that's slightly better will like get like keep growing and the one thing slightly worse will keep getting less right and eventually either that smaller species will have to change its niche or it will just die out completely so niches are exclusive right exclusion due to competition competitive very nice alright so this concept of niches and how like all these species have different like roles plays into the concept of biodiversity okay and this one's a pretty important one you don't really know that much about it because like the word is literally biodiversity right diversity of bio but the concept is that it's not only the number of organisms right like you might have a ton of organisms but if they're all the same species are you really that diverse so essentially biodiversity matters on two things right species richness and relative abundance so obviously you need a lot of species to be biodiverse right but also you don't want all of those animals to be one species instead of like one dude of the other of the other species right so that's why relative abundance is also important because you want all the species to be relatively evenly represented so if we look at an example right let's just say there's three species a b and c and then environment one and environment two there are 10 10 and 10 but in this other environment there are like 18 1 1 right now clearly it seems logical that one has more biodiversity right because they have the same species richness right they both have three species but this guy has better relative abundance right they're both they're all equally approximately equally the same okay i'm probably equally the same i'm too good at this game bruh but yeah you guys get the idea probably isn't too much else to say about biodiversity though so let us move on okay so i just want to throw in two more things about species right um there's two main types of species in these environments right so there's basically a foundation species so it's basically a foundation species and these are basically the ones that the entire environment is built off of right so like corals for example they make up the entire backbone of coral reefs right and then for like forests i'm assuming trees would also be a foundation species all that kind of stuff then they're also keystone species and these guys are basically the ones that even if they're a very few of them they actually have a very disproportionate impact on their environment so for example the beaver the beaver is my favorite animal now but the reason why beavers are keystone species right is because they're very few like even one beaver right and they can make a dam and completely change the entire like ecosystem right because the river is very different from a lane and if you out of them you're changing a river to a lake so just remember foundation are basically species that they're a lot of and they basically build up the entire environment and then keystone basically means that even though they're very few of them they have a very very big impact on the on the entire ecosystem okay and now finally we are on to the last topic which is human intervention so how have humans been changing the ecology of their like ecosystems right so one way they've done that is through invasive species and these species are pretty self-explanatory right like a human brings one animal from one place to another and these species are often way able to like colonize the entire thing because they are there they didn't evolve there right so essentially they might have an unfair advantage over all the inhabitants that are already there like a pretty good example is like the brown tree snake that was introduced to guam or something and basically the birds there never had any predators and when you had a snake there they don't have any defensive so the snake basically kills off all the birds and this usually happens because those species don't actually have like natural predators in the new location right so they not only have nothing to control them but they also have an easier time catching prey because their prey is not adapted to avoid them then of course humans use a lot of resources right so of course there's renewable and non-renewable resources right and we tend to use the non-renewable type right we use fossil fuels and all that stuff and basically that's releasing a ton of carbon dioxide into the atmosphere and then you guys probably know that when we release carbon dioxide into the atmosphere that causes global warming and climate change because essentially carbon dioxide traps in a lot of the heat so that eventually leads to increased temperature and essentially the idea is that climate change has actually shifted a lot of the ecosystems right like you we've been pushing up like the arctic circle we've been pushing down antarctica we've been like endangering a bunch of the animals that depend on like on these polar ice caps and that kind of thing so in that way climate change has been disrupting a ton of ecosystems and then of course there are extinctions right so essentially when an animal species disappears completely the no left living individuals of that species it goes extinct and basically it said that we've been causing the sixth mass extinction because essentially we've disrupted so many environments that like a like a way higher amount of species have been going extinct recently because of human intervention so to remember that extinct means that they're completely gone endangered means they're about to be gone and basically as these species go extinct we're reducing biodiversity which has a very bad like consequence on like ecosystem because essentially biodiverse ecosystems are actually more productive than not biodiverse ecosystems all right very nice so now we are finally done with the entire unit um there's a lot more stuff in the book but it turns out that it's not very covered on the ap exam so everything in this video should have been the main stuff covered in the ap exam if you guys have any questions let me know down in the comments below as always if you enjoyed the video leave a like and subscribe for more thank you guys for watching again and see you guys next time