hey everyone welcome to topic 1.1 of ap environmental science this is introduction to ecosystems in daily video 1 we're going to cover predator prey relationships as well as some basic background information on ecosystems and we're going to focus on how the availability of resources influences species interactions before we get further into the video i'd like to introduce myself my name is lisa bagley i've been teaching apes since uh 2010 here in the dallas area i currently work for mesquite isd at west mesquite high school and i am excited to be part of your educational journey for apes so here here we go what are we going to learn today let's find out we're going to focus on learning objective ert 1 a so what is that well in this video we're going to explore how to connect the essential knowledge which is what you need to know in this course the nuts and bolts to the science skills which is how you have to show what you know on the actual ap exam we're going to review some basic characteristics of ecosystems focusing on biotic and abiotic interactions you may be familiar with those words from previous courses we're going to begin to explain how the availability of resources influences species interactions which is our learning objective that's the ert1.a and we're going to discuss some aspects of predator prey relationships so what exactly is an ecosystem well it's a community of living organisms that's the biotic part in conjunction with the non-living components of their environment that's the abiotic part and they interact as a system ecosystems are the result of both biotic and abiotic interactions and that's our enduring understanding so you're going to see that enduring understanding of biotic and abiotic interactions as well as our lo our learning objective about um how species how resource availability influences species interactions woven throughout these videos so here's a question for you based on the definition above the definition of ecosystems take a look at these scenarios that are in the fat bubble here and consider which of them might be an ecosystem interaction you can pause your video and take a look at those be sure to justify your why based on that definition of an ecosystem i'll see in a second so let's talk about some biotic and abiotic components of ecosystems the biotic parts of ecosystems are the living parts they include things like producers plants photosynthetic algae phytoplankton herbivores carnivores omnivores detritivores and soil soils in that living category but we also have abiotic factors in ecosystems those are the non-living parts such as sunlight temperature precipitation moisture or water levels the ph of the soil or the water and soil there it is again in the abiotic factor list so consider this why is soil in both the biotic and the abiotic lists let's take a look at the big picture for species interactions here interactions in ecosystems between species can include three major categories that the college board would like you to know the first is predator prey relationships and if you take a look at some of the images that are over there on the side of the this slide you'll see a grizzly bear with a salmon in its mouth that is a predator-prey relationship interactions can also include symbiotic interactions such as mutualism commensalism or parasitism and we'll get to those in a subsequent video if you take a look at your images there we've got a clown fish hanging out in a sea anemone that is an example of mutualism we also can have competitive relationships and competition can happen between different species or within a single species so your final image here is many different species on an african savannah and they are surrounding a resource there and they may or may not be competing over that abiotic resource so again as we consider each of these interactions we're going to try to identify the biotic or the abiotic resources that are driving the interaction in each scenario and we're going to explain how the availability of those resources the species interaction because that's our learning objective okay time for the nitty gritty this is essential knowledge ert 1.8.1 it is the first essential knowledge piece that is uh in ap environmental science and this is predator prey relationships in the simplest terms predators hunt and kill their prey that's what they do this is a biotic interaction these are two living species that are interacting in this exchange for predators the prey is a food resource so as we loop back in to our lesson objective and our enduring understanding how do we how does resources drive the interaction the prey is a resource it's a food resource for the predators so the final part of this is as the availability of the prey fluctuates the numbers of the predators do as well and that again goes back to how does the availability of resources influence in the interaction something to consider as we move forward based on your prior knowledge of ecosystems how do we normally classify a prey species when we're talking in terms of trophic structure what about a predator species you're going to learn more about these later in unit 1 but i want you to kind of think about that as we move through so let's do some practice we're looking at here a graphical stimulus that was pulled up from ap resources so when i'm talking to students about how do we approach a graphical stimulus in ap environmental science there's a couple of steps that i'd like you to go to that will help you understand a graphical stimulus and help you get to a better and more thorough answer so the first thing i'd like you to look at is what is the title of the graph the title of the graph in this particular regard is predator prey oscillations over time the title of a graph can actually tell you a lot about what is going on in the graph titles should be descriptive so taking a look at that's going to give you some information you may or may not be familiar with the word oscillation to oscillate means to go up and down or have a regular periodic um peak and valley over a certain time period so once we've looked at the title let's take a look at the x-axis and the y-axis in this case it's axes because there are two y-axis axises axes so time is across the bottom here that's our x-axis and in this particular case time does not have any um there's no hash marks there's no it doesn't tell us years or anything like that we just know the time is going from some time in the past to sometime in the in the future time is moving uh linearly from left to right our um two y axes we've got one that says prey population size and if we look at our key here the prey is the solid line and then we've got predator population size and the predator is our dashed line so now we've got an idea that we're comparing prey and predator population sizes across some type of time period so the final question that i'd like you to take a look at for this particular part of the graph is what is the what did the the lines look like on this graph describe the trends that you see in the populations over time what are your observations well the title tells you that that the lines are oscillating they're going up and down on kind of in a regular manner but you can see that those lines don't completely overlap exactly and that the peaks and the valleys aren't quite the same so we need to kind of think about that so overall picture here and i'd like to draw your attention down to the bottom of your screen we are right now doing science practice 1.a which is a description of environmental concepts and processes this is a foundational skill for apes you'll be asked to do this throughout the ap exam and we're going to practice this a lot okay same graph but let's go into it a little bit further and when we're looking at this when we're describing what this graph looks like i might say something along the lines of as the number of prey increase the number of predators also increases that's what i'm seeing there and as the number of prey decreases the number of predators also decrease okay that's fair enough it's right there uh right there in front of you um but there's this lag here so consider why am i there why is there a lag between the peak of the prey population and the peak of the predator population you can see that the the peaks are uh they're subsequent but they're not they don't overlap the other thing i'd like you to consider is why is the population size why does that peak higher for the prey than for the predator and i want you to think back to the question that i asked before about where those populations fall on a trophic structure okay finally when we're taking a look at a graph like this a fully realized free response question might ask you to consider other factors um something other than predation that might cause the population of predators or prey to fluctuate there are other things in ecosystems that can cause changes in predator and prey populations and you might be asked to consider those as well all right so let's check for some understanding from this video can you identify the key aspects of predator prey relationships can you describe how resource availability the prey influences the predator prey relationship and can you describe key aspects of the predator prey relationship if it's shown in a graphical format if you can then you got it congratulations thanks for watching and i'll see you in the next video