welcome back to environmental biology it's heather lytle again your teacher and i wanted to introduce ecosystems this week it's actually chapter five in your textbook this week in our lesson we're going to look at understanding how ecosystems sustain human societies define ecology outline a hierarchy of biological organization describe an ecosystem and its major components and interactions describe energy transformations across trophic levels and explain the structure of biogeochemical cycles you'll also be able to illustrate abiotic and biotic interactions and symbiotic relationships at the end of this chapter our textbook opens up with a story about lake washington which is just east of seattle and this example of lake washington is perfect because it shows the value of balance within an ecosystem it was noted in the mid 1900s that the lake was becoming very turbid very cloudy and the fish were dying and they noticed that there was wastewater that was being dumped into the lake which is full of different nutrients these nutrients cause the algae to bloom and which uses up the oxygen within the lake and the fish were starting to die so there was a huge problem within lake washington they called in environmental scientists and they began to do some studies to see what was going on and they noticed a relationship as we look at this graph the top graph you see that the the gray area is the amount of dissolved phosphorus in the sewage effluent and the the red line is the total dissolved phosphorus so you can see that in the 60s this was starting to grow in the lake and the amount of phosphorus was directly related to the amount of sewage effluent that was discharged into the lake if you look at the next graph you can see when they started to control the effluent the the after 1965 the amount of phosphorus declined the chlorophyll started to decline as well the chlorophyll is actually an indicator of the amount of algae that were in the lake and so there's a direct relationship between that and the main point of the story with all of this is that everything is tied together the nutrients the the abiotic parts the water the biotic parts of the system the fish and the algae everything is tied together this interaction between organisms in their environment is called ecology and it is an actual interdisciplinary science that involves biology botany um invertebrate biology vertebrate biology geology chemistry all those different parts so if you really like science and can't figure out exactly what field you want to study ecology is a great thing to go to when we look at the different hierarchy or levels within an ecosystem we can start at the bottom and look at the the individual species these are all organisms of the same kind that can reproduce together so if we were talking about uh in our common part of the state we could talk about cottontail rabbits cottontail rabbits would be a species if i talked about all the cottontail rabbits within denton county i'd be talking about a population and so that's a group of the same species in a given area at a given time when you combine the rabbits and the coyotes and the mice and the humans and the dogs in denton county then you're talking to the community level the ecosystem that we're referring to that involves the rabbits would be the cross timbers forest in denton county and so that would include the the trees the lakes the the where the cities are where the people are where all the different organisms are that would be an actual ecosystem altogether another part of chapter five is going to be talking about energy energy transfer within an ecosystem and energy is the ability to do work and it's measured in jules you might think well this belongs in physics well it's actually a key to understanding biological principles as well there's two kinds of energy we could talk about energy of motion which is called kinetic energy we could also talk about potential energy which is stored energy chemical energy from food it could be a rock at the top of the hill it has the potential to do work but it's not doing work quite yet when heat is transferred from one system to another we call that thermodynamics and sir isaac newton came up with three laws we're going to talk about two of them today the first law is the conservation of energy the energy is neither created nor destroyed it just changes forms it's transformed and so we're going to talk about the sun being the source of energy in our ecosystem and how that's transformed between the different layers of the food chain the second law of energy is entropy that entropy increases within a system and with each successive energy transfer in a system less energy is available to do work energy is lost but we do require energy to maintain biological systems within our living systems the energy for life the principle source of energy is the sun and we have primary producers in our ecosystem the plants which are going to be able to photosynthesize and capture that sun energy another primary producer would be extremophiles which are kind of bacteria they're known for living in extreme environments like in the mouth of a volcano and they can perform certain biological pathways like chemosynthesis and they can get energy from inorganic molecules like hydrogen sulfide through photosynthesis the primary producers will use sun energy to make chemical energy in the carbon to carbon bonds inside of glucose sugar it requires chlorophyll and that's the green pigment implants it uses carbon dioxide and produces oxygen as a byproduct so even as plants photosynthesize they're making energy for themselves but they're also producing the oxygen that we need in order to breathe cellular respiration is the opposite reaction of photosynthesis and it's going to take the chemical energy from glucose and break it down it's going to use oxygen in the process and produce carbon dioxide and atp energy this is required by all living things and as part of why we need oxygen in order to breathe when we talk about the trophic levels of a food chain this probably will be familiar to you from either private previous science classes but the sun is the ultimate source of energy and it's captured by primary producers because they have chlorophyll and they're able to photosynthesize the primary consumer would be an herbivore that would be an animal that eats a plant so that would be a primary consumer a secondary consumer would be the next level up they eat the animals that eats the plant and so we would call them carnivores if they also eat plants there's a word called omnivores if they eat all plants and animals and then usually a food chain would have a tertiary consumer it would top out at the fourth level and that would be an animal that eats the other animals and this little picture looks nice and neat but actually in reality it's more of a food web what's important about the trophic levels is that we want to see the energy transfer within these different levels and so if you looked at the amount of energy in the sun only about 10 of it's going to be captured by the primary producers the animal the primary consumer that eats a plant is only going to get about 10 percent of the energy that's available in the plants he's going to lose some energy from uh either the waste that he produced that it's not uh metabolized in him it's it's actually excreted out of him or maybe he has to use energy to catch his food or to travel to get more food or he may not be able to eat all the the food that's available and he's also going to lose some heat as thermal energy as he has metabolism but as you go up the successive levels of the food chain you lose 10 you you can only gain 10 to take up to the next level and so 90 of that heat is going to be lost that's why predators at the top level of the food chain have to eat a lot more food because they only get 10 of the energy available at the previous chain the next part of chapter 5 talks about cycles and part of your homework we'll be watching a video on bozeman biology that will actually give a really good description of these different cycles so i'm going to go pretty quickly through this one other thing that's really neat though is this quote from john muir he's a conservationist and he said that when one tugs at a single thing in nature he finds it attached to the rest of the world and this is just beautiful because it just shows how everything is connected together and you can find a ecosystem needs to find its balance in order to to be its uh most productive we're going to look at the water cycle carbon cycle nitrogen cycle sulfur cycle and phosphorus cycle the hydraulic hydro hydrologic cycle involves both the the surface water the groundwater and atmospheric water and so we can look at the different pieces of that we can see that there is evaporation from the ocean water we can see precipitation over the ocean as well as over the land we see movement of moist air from ocean to land which causes our weather patterns transpiration is the removal of water from our vegetation also evaporation from soil streams rivers and lakes and we get percolation of surface water down into groundwater which is something that people sometimes forget about but that's another another part of the water cycle the carbon cycle um involves a lot of co2 and um which is produced by plants that photosynthesize but it's also used by the burning of fossil fuels um we also can talk about carbon sinks and these are areas where you see a large amount of carbon in organic matter so in the limestone under our ground and we also have oil and coal and gas deposits underneath and those are going to be carbon sinks we have large forests which are carbon sinks and these carbon sinks are very significant there's a huge impact of humans on these carbon sinks as we um mine for coal or as we drill for oil as we burn forests and reduce the amount of vegetation that's on our planet and all of this burns carbon dioxide and puts it into the atmosphere as well as depletes the carbon sinks another source of carbon is the shells from different marine invertebrates another cycle is the nitrogen cycle and the nitrogen cycle um most of the amount of nitrogen in our world is atmospheric nitrogen which is in the form of n2 it's just a gas but that's not usable by living things living things need nitrogen in order to make dna in order to make proteins and so it's a necessary element in living things so what's real important is that we need nitrogen fixers which are usually bacteria that can transform nitrogen from n2 into ammonia which can be used by living things in order to make dna and protein the human impact of the nitrogen cycle would involve fossil fuel burning we release nitrogen oxide into the atmosphere which is combines with precipitation to make acid rain that nitrogen oxide is also a greenhouse gas and too much nitrogen like a fertilizer gets run off and goes into rivers and streams and lakes can cause eutrophication or blooming of algae which can cause problems to the fish population the last cycle is the phosphorus cycle this is an interesting cycle because it's the only one of these cycles that doesn't have an atmospheric component most of the phosphorus is found in rocks and so as it rocks erode then you can add phosphorus to the water systems we can also get phosphorus into the water systems through fertilizer that is runoff and again fertilizer or phosphorus is a growth stimulant for algae in the water which can use up the oxygen if you get too much and can cause the fish to die the sulfur cycle is our last cycle that we'll talk about and when i think about the sulfur cycle i think about emissions from volcanoes but it can also be produced by the the burning of petroleum and smelting processes that's one of the human interactions but large amounts of sulfur dioxide and sulfur aerosols can get into the air can be combined with precipitation and cause acid rain there's different kinds of biotic interactions that are important in ecosystems and we can talk about symbiotic relationships which are usually a positive type of interaction mutualism is when two organisms both benefit so we can have the clownfish and the anemone are both benefiting from their uh symbiotic relationship another type of relationship is called commensalism and that's where one organism benefits like the barnacles on the back of the shot of the turtle shell and the the turtle doesn't actually get a benefit he's kind of neutral so commensalism is just where one organism gets the benefit of the relationship another type of symbiotic relationship is parasitism and this is an example of a deer tick and the deer tick benefits by getting the blood from the host but the host gets a negative effect because of the deer tick because you might be able to contract lyme disease different viruses and pathogens can be transferred through the tick to the human host and so there's a harmful effect to the host other type of interactions would include predation the basic predator prey and we also have competition which can be between two animals of the same species or maybe between uh two different species but they're competing for resources the keystone species is super special in ecosystems because when they are removed from the system you see a total shift in the whole ecosystem balance so here's an example of the gray wolf and when its population is high the elk are under control when the gray wolf is has a low population then the elk go out of control and so it's really important to have a natural balance with the predator and the prey and so the keystone species is key to that system so this week for your homework um you're going to watch video 2 which you just completed you're going to read chapter 5 in your book and then also watch the bozeman video and biogeochemical cycles if you have questions feel free to email me or come see me during my office hours and i'll be glad to visit with you i hope you enjoy learning about ecosystems