okay so here is our last unit uh in ap bio unit eight ecology and so our first couple like standards or essential knowledges start with a discussion of organisms and how they respond to their environment now for this there's not really a direct thing to teach it's not like a pathway or something but rather just different examples so in plants that might be phototropism where they grow towards the light or photoperiodism where they bloom depending on if it's a long day i like lots of light or a short day plant with like um the sun sets earlier like so like in wintertime uh we have things like hibernation um or broomation i think it's called if you're a reptile you have circadian rhythms with um like sinking your gene expression and your hormone levels to the rise and set of the sun we have changes in gene expression with for example fur color in animals that live in the arctic and so this you could have a variety of questions actually that might come up from this it's a pretty vague or general topic now the next standard talks about organisms exchanging information with one another in response to internal changes and external cues which can then change behavior so the example i chose was pheromones so we actually can communicate with chemical cues that come off of us that can then send information to nearby individuals which will then change their um internal conditions so for example may be involved in mating certain pheromones released from um like one sex can then influence uh reproduction in the other sex or of the species so like with male or female fish here we also have things called alarm pheromones so if you have um like in the picture on the left the little mouse that's in danger is going to actually release some pheromones that nearby mouse or mice can detect and then that will alert them and put in them into a fight or flight response so i feel like um exchanging information could be pheromones but it could also be alarm calls or other types of communication so animals can communicate or organisms can communicate in different ways we have visuals so that would be things like the fireflies lighting up or um when a dog has its hair stand up on the back of its nest neck or when like humans blush that's all like visual communication we have auditory so with whales singing or howling tactiles like touch so for example when baboons groom each other that's going to be a sign of affection and then you have chemical which is kind of like those pheromones i just talked about or like scent um and now ants will use pheromones for marking the trail you also have pheromones are really used to in bees like with male uh bees uh the female will release certain uh pheromones that will actually alter gene expression in uh uh bees around her so um different ways that we can communicate and act on it now when we talk about um oops let me go back so communication though has a variety of mechanisms so you have signaling behaviors that can produce changes in the behavior of other organisms and so here you have like two wolves maybe like being submissive or not and then we also have visual audible tactile electrical and chemical signals that can be used to indicate dominance find food establish territory and ensure reproductive success so i feel like here there's a wide range of things that could be asked about now uh responses though to information and communication are vital to natural selection and evolution so if a species is unable to communicate or respond to signals that may lower their fitness and therefore the those types of communication and learned behaviors can be selected for um or against so here i have like these little ducklings they actually will imprint on their mother and so when they hatch they will um like stick with their mother that's like an innate behavior and think about it any little duckling that doesn't have that behavior that innate attachment to the mother uh will have low fitness it won't be protected it won't be guided i won't survive um same thing with the sea turtles the sea turtles uh they are have this innate once they hatch they see the light and their behavior is to move towards the ocean um and if they don't then they don't survive and so actually right now when we have artificial city lights near beaches where there's sea turtles hatching sometimes they'll confuse the city lights for moonlight and they'll actually go towards the streets um and so that's how we know that it is innate um we also have like here in this goose it's called a fixed action pattern where this if the egg rolls out of the nest the goose once it starts this behavior of egg rolling and returning the egg to the nest it actually has to finish the behavior like it can't stop halfway so even if she sees the hand remove the egg she will finish the behavior and that's a behavior that's innate and hardwired into the like neurons and um from mother geese that don't do this behavior and their egg rolls out of the nest they their babies have a less chance of survival so it's low fitness now other examples would be used in like um uh behavior for reproduction so on the left here i think it's a cuttlefish that does these intricate designs uh to attract their mates um you have the other three are all bird behaviors uh for courtship rituals and any birds that don't have these innate instinctual drives to attract the opposite sex would have low fitness because they won't get to reproduce now we also have things called cooperative behavior and in cooperative behavior that tends to increase the fitness of the individual and the survival of the whole species so if you are the whole population if you look at the picture on the right how the wolves will work together to take down their prey so that cooperative behavior increases their own individual fitness because by working together they have a source of food and it also helps for the whole survival of the population okay then we have let's go ahead and break this down a little bit so here we talk about energy so there's different strategies that organisms have you can either be an endotherm or an ectotherm and endotherms are going to use like thermal or heat energy to maintain a constant body temperature in homeostasis so where do they get that heat it's through metabolism so by doing cellular respiration and breaking your food down in your mitochondria that generates heat and that heat is going to be used to maintain homeostasis so if you look at this um pie chart here if you look at a male penguin that is four kilograms and then a ball python that is also four kilograms and you look at the amount of calories they require per year the penguin is requiring over 300 000 calories kilocalories per year while the python is only 8 000. now you see in the two species the different ones though a thermoregulation the orange part is uh um where the energy those calories are going towards so you can imagine a male penguin in the cold is going to require lots of calories to generate heat now if you look at that little deer mouse though and you see a lot of its calories are going towards thermoregulation this ties into unit 2 with surface area to volume ratios that little mouse has a very large surface area compared to its volume so it loses a lot of heat to its environment and therefore needs to have a higher metabolic rate designating more of its calories towards thermoregulation to make up for the heat that's lost to the environment now the penguin though has insulation it has fat it has well feathers it's going to insulate and trap a lot of that heat for it now you can look at like this graph over here on the left with the bobcat and the snake you can see how the bobcat's body temperature stays pretty constant no matter what the ambient or outside temperature is compared to the reptile the reptile is going to have its body temperature is dependent on the outside temperature okay now when we look at um reproductive strategies okay so we have two kinds of species really you have r and k well not just two kinds but we classify them as either r or k uh selected species and really that comes down to their strategy for reproduction now this does tie into carrying capacity though so let's look at the graph on the left first and so here we have um if you think about r our little r stands for rate of growth or like um growth rate so in exponential growth you have a pretty high growth rate i'm at that bottom part of the graph and so that's where like cockroaches in this graph would be in our selected species their strategy for reproduction is to put a lot of their energy towards making tons of offspring in our selected species they make tons of offspring with the hopes that a few will survive and that's where you see in the top right graph right here this blue line how you read this are selected species as a type three survivorship curve is that they have if you look at the um things that says number of survivors so if you start at the thousand they don't have many survivors very few actually survive to old age uh to the hundred percent of the maximum lifespan so their strategy in life is to just produce a whole lot of offspring and hope a few survive to adulthood versus a k selected species a k selected species their population probably already lives near carrying capacity so if you are a species living near carrying capacity and k is the little letter for carrying capacity that's why these are k-selected species k-selected species live at or near carrying capacity and it's already tough to survive there's already limited resources and density dependent limiting factors so therefore their strategy that has evolved is to have few offspring but lots of parental care so it comes down to where are these organisms putting their energy our selected organisms are putting their energy towards producing lots of gametes and offspring a bit little to no parental care versus k-selected species are putting their energy towards raising their young they have few offspring but the chance of their few offspring surviving to old age is high so as a human i have two offspring and i'm raising them for many years are hoping to ensure their survival to old age so that is where i put my energy and my resources as a k-selected species now if you look at the survivorship curve up here in the type 2 the type 2 the chance of mortality is even at any age so that isn't really an r or k selected species all right so now uh when we look at this is tying in that metabolic rate that i talked about earlier with the mouse how the mouse had a very high metabolic rate and that's because the energy we take in as endotherms is going to be used to generate heat so we lose heat to our environment that's part of our like evaporative cooling but that's not good if it's really cold outside and you're losing your heat to the environment so you can see this graph how the surface area to volume ratio of the organism matters when it comes to calculating their metabolic rate and how many calories they're going to have to burn through to generate heat so the smaller the organism as the less volume but the more surface area compared to that volume the higher the metabolic rate compared to an animal like an elephant who has a larger volume compared to its surface area so the surface area volume ratio is not as great but a lot of their heat is going to be trapped on the inside and not lost to the environment and so they would have a smaller metabolic rate now also elephants just to talk about evaporative cooling those large flat ears are to increase surface area to like have heat evaporate for cooling off all right now if we look at this next one about um energy so a a net gain in energy results in energy storage or growth of an organism but a loss in energy results in loss of mass or ultimately death of an organism i think that's kind of like a uh hopefully a common sense standard um okay and then we look at changes and energy availability can result in changes in population size so i chose the predator prey relationship graph to explain this standard because when we think about a changes in energy availability if you are the predator your prey is your available energy so if we look at the uh links is orange here so if you look at like 18 let's go to 1870. you can see look at 1865 and let's look at the prey the hair which is a rabbit so after 1865 you see a decrease in the hair population now that's food for the um links so the predator so if the hair or the rabbit population decreases it follows that the links are going to start to starve and not have a lot of food so their population size declines so that is why you see a little bit of a lag time a little bit later that orange line around 1968 or so starts to decline now once the lynx population goes down though the predator and the prey population increases that will be followed by an increase in the predator because now they have energy available to them this also um can be tied into uh producers and different trophic levels so when you look at an ecosystem or a community really its structure is going to be dependent on the energy that's available in the producers so the producers you have at the bottom if there's a drought and the rain doesn't fall and the crops die or if there's like a lot of volcanic eruptions or air pollution and the sunlight is blocked and the crops can't do photosynthesis so you have a decrease in photosynthetic activity well then you have a decrease in available food or available energy so if that bottom trophic level decreases it follows that the trophic levels above will also decrease but in the opposite if you have like in southern california here we have el ninos periodically we're gonna have lots of rain over our winter time so we have lots of rain and we have lots of plant growth we have these things called super blooms and then if you have lots of producer activity lots of growth well now you can support more herbivores and therefore more secondary consumers etc so uh there we go now when we talk about energy in an ecosystem we have two sources we have photosynthesis but there's also something called chemosynthetic organisms or chemosynthesis which is going to be like at the bottom of our ocean near hydrothermal vents because we really just don't have sun reaching miles and miles down to the bottom of the ocean so therefore they need a different source to start basically like that calvin cycle and that building of organic molecules and so that source is going to be from the hydrogen sulfide and the chemicals coming up from the hydrothermal vents all right so now that's autotrophs we have two kinds uh photosynthetic organisms like plants algae protists phytoplankton cyanobacteria but then you also have chemosynthetic organisms that you would find in the bottom of the oceans now heterotrophs though they need to eat to get their energy so we cannot do photosynthesis and really when we think about heterotrophs we get our energy okay in unit 3 on cellular respiration we talk a lot about breaking down glucose and carbohydrates but in reality we can also use lipids as well as amino acids or protein for our energy sources the macromolecules basically can enter in different steps in the cellular respiration pathways so glycolysis would start with glucose but if you're breaking down fatty acids you would just start right at the krebs cycle in aerobic respiration now amino acids have bonds to be broken as well and so some amino acids can like cut in line in the glycolysis pathway and then other amino acids can start in the citric acid cycle but really we're trying to get those electrons for the electron carriers for oxidative phosphorylation okay now let's go on to populations um so in populations uh they are made of individuals that interact with one another and their environment so i think it's kind of beautiful to think about a population in population ecology we talk about how biotic and about factors can influence density distribution and size of a population and really these members in the same population so a population is defined as the same species in a designated area and these members in that population are going to compete with each other for resources are they experiencing the same abiotic as well as biotic factors and they're likely to interact and breed together and so this is also where when you have that struggle for resources in a population especially as density dependent limiting factors come into play you're going to have the consequences of natural selection in a population not all are going to survive so as they struggle to live together and compete against each other you'll have natural selection and survival of the fittest driving possibly the evolution of this species okay so when we talk about populations and how they grow we have two models we have the exponential growth model as well as the logistic growth model and in exponential growth this population is going to grow as if there's unlimited resources so it's going to grow exponentially and the formula is r which is rate of growth times capital n capital n stands for population size so in exponential growth it's growing as if there's unlimited resources and limiting factors aren't aren't an issue now you will find exponential growth uh in situations like following a forest fire or something like all of a sudden this habitat has been cleared now there's like room for exponential growth but in reality a population will reach a density that becomes unsustainable so as you are are growing exponentially eventually resources are going to become limited there's going to be a fight a fight there's going to be competition there's going to be a challenge to survive so right now the human population we are growing exponentially and eventually we will experience an overshoot some uh some people some scientists predict or question are we already past our carrying capacity are we still not there yet so when we think about population density that is how many individuals there are per unit area and as our population density increases if the as okay i love this as the population grows the competition for resources becomes very great and not all if you go above carrying capacity not all members are going to survive so what we call that part is the overshoot and then you'll have a dip and then they'll survive and then oh too many and back and forth back and forth and eventually that like average is called the caring capacity and that is how many individuals that can be supported in a given area and so as a population though grows uh exponentially logistically or logically they're going to reach a limit and so we call this type of growth logistic growth and that involves carrying capacity so if you're doing math for this and we're looking at the rate of growth and the population size but we also take into consideration that there's a limit and there's going to be um like a slowing down so this is the part i find super fascinating let me see if i can write on this for you so right around here the rate of growth slows down because not all individuals are surviving that are born and then right around here when it's flat the number of births and the number of deaths are equal the rate of growth is zero when you reach carrying capacity okay let me erase this okay uh now when we talk about why a population would reach carrying capacity though that is where we have things called limiting factors and we have density dependent limiting factors as well as density independent limiting factors density independent would be thing like things like natural disasters right like that doesn't it doesn't matter your density if there's a forest fire or a flood individuals are going to be limited on how much they can grow there's going to be death however in population density limiting factors or dense sorry density dependent think about as the population grows any factor or anything that's going to make it harder to survive we call that a density dependent so as the density increases disease is going to spread a lot easier so i'm recording this um in 2021 after we've lived through a covid and a pandemic and this is why we have social distancing because when we're really close disease can spread really easy so that is a density dependent limiting factor we also have predation so the more individuals in a population the easier predators are going to have at getting food so that'll keep the population in check and then competition between each other as population size increases exponentially you're going to have individuals of the same species competing for the same resources because populations live in the same area so it's going to be limited at a limited amount of food space shelter water nutrients in the soil sunlight there's going to be competition for available resources and as the population approaches carrying capacity that competition will get more fierce and there'll be a greater struggle for survival which is where natural selection comes into play okay so now we're switching gears and kind of moving into oops i'm still on a pen as we're going to move into move into uh community and so when we talk about so populations are individuals of the same species breeding and interacting together in an area versus a community is all the different populations interacting together but we can actually talk about the structure of a community and talk about it's like resiliency and how healthy that community is all right so let's talk about this so here if i have um species diversity so that's all the different species that are within a community you have what's called species richness which are the number of different species in a community as well as relative abundance which is like how what's what's their proportion within that community so let's go ahead and look at two examples here so here we have community a and community b and we can see here that the species richness is the same in both communities here there are four species of trees however their relative abundance is different in this one on the left i made it where it's all equal they're evenly dispersed whereas the one on the right is made up of majority this like oak looking tree so um when we talk about why this matters is let's pretend there's an invasive species and this invasive species is all through the west coast of the united states it's called a bark beetle and this bark beetle actually gets inside of trees and eats the bark or the tree from the inside out killing it so let's say it attacks this particular tree well in both communities um if that tree were to die off you can see how community a is more resilient and not as greatly affected because they had a greater relative abundance of different variety of species and so therefore when you have an ecosystem or a community made majority of just one species it's less resilient to things like invasive species viruses pests humans etc and so the more variety you can have the greater genetic and species diversity you can have within a community the more resilient it's going to be to change okay but communities can change over time depending on how different populations interact so a community are the different uh populations living together and interacting together so you can think about like in a food web how if like the number of boxes for some reason like greatly increases then the amount of mice and rabbits will decrease like their numbers are all dependent on each other or earlier we talked about like predator prey uh relationships but this would also tie into like keystone species and trophic cascades and really keeping in mind that all species do interact together and they influence each other okay um and so interactions among or between these populations determine how they access energy and matter within a community so energy and matter is really coming down to food if you are a heterotroph so that could be like competition um it could be um predators but really when we think about plants their matter and energy is photosynthesis and so they have competition in their own roots or if one plant grows above the other and put shade on that next one so there's actually