1 Ecology and EcosystemsStructure and Function Ecosystem Concepts and Impacts
2 Structure and FunctionThe structure of ecosystems comprises all it’s species. The greater the biodiversity, the more complex the structure The function of ecosystems includes energy flow and biogeochemical cycling Perturbations to ecosystems that significantly affect structure will affect function. Perturbations that significantly affect function will affect structure.
3 Structure and FunctionBiosphere Ecosystems Communities Populations Organisms Structure and Function The biological organization of the ecosphere ranges from molecules and cells in organisms to the entire biological community of the Earth. An ecosystem can be defined by “natural boundaries” that define a recognizable unit of structure and function
4 Structure and FunctionEcosystems comprise biological and physical/chemical compartments that constantly interact hydrosphere lithosphere biosphere atmosphere
5 Structure and FunctionThe structure and function of all ecosystems is driven by the quantity and quality of energy input. For most ecosystems, the ultimate energy source is solar radiation. Energy received by ecosystems is used to build trophic structure and biodiversity and to cycle materials through ecosystems.
6 Energy Flow - the Earth SystemEnergy is constantly being emitted by the sun (mostly as light) and travels through space at about 186,000 miles/sec. Fortunately for us, the Earth get in the way of a small fraction of that light, and this energy drives a good part of the Earth System. Of the light that we intercept, about 34 % of it is reflected back out to space, mostly by cloud tops, but also by brightly colored land surfaces. The remaining energy is left to interact within the Earth System We refer to this interaction as the “Heat Budget”.
7 Heat Budget Reflected Light (34%) Light absorbed by the oceans (23%)Light absorbed by the Land (42%) Light absorbed by Photosynthesizers (0.2%) Heat re-radiated back out to space (66%) Energy in = Energy out Solar radiation Reflected by atmosphere (34%) UV radiation Radiated by atmosphere as heat (66%) Lower Stratosphere (ozone layer) Greenhouse effect Visible light Troposphere Absorbed by ozone Heat Heat radiated by the earth Absorbed by the earth Earth
8 Biogeochemical Cycles Heat in the environmentBiosphere Carbon cycle Phosphorus cycle Nitrogen cycle Water cycle Oxygen cycle Heat in the environment Heat Heat Heat
9 Structure and FunctionTrophic structure describes the relative abundance of species at increasing levels of distance from the source of energy in a food web. Ecosystems with high biodiversity have many different species that occupy the same trophic level. This is why high biodiversity provides complex structure to ecosystems. Trophic structure, determined by biodiversity determines how energy flows through an ecosystem.
10 Trophic level Trophic level Trophic levelHeat Abiotic chemicals (carbon dioxide, oxygen, nitrogen, minerals) Solar energy Trophic level Trophic level Decomposers (bacteria, fungus) Producers (plants) Consumers (herbivores, carnivores) Trophic level
11 HEAT producers Energy from sunlight HEAT NUTRIENTS primary consumersdetritus feeders and decomposers HEAT Figure: 29-01 Title: Energy flow, nutrient cycling, and feeding relationships in ecosystems. Caption: Note that nutrients (purple) neither enter nor leave the cycle. Energy (yellow), continuously supplied to producers as sunlight, is captured in chemical bonds and transferred through various levels of organisms (red). At each level, some energy is lost as heat (orange). higher-level consumers HEAT
12 Energy Flow Through the Biosphere Food ChainsFood Chain—Community of Organisms Formed by Trophic Levels First Trophic Level—Producers Second Trophic Level—Primary Consumers (Herbivores) Third Trophic Level—Secondary Consumers (Carnivores) Fourth Trophic Level—Tertiary Consumers Decomposers (Microconsumers)—operate at each trophic level NOTE— The amount of total energy passed from one level to the next is decreased (because of heat loss) The number of organisms at each successive level is less The total biomass decreases at each successive trophic level.
13 Freshwater Aquatic Food Chain Energy PyramidTertiary Consumers-> Secondary Consumers -> Primary Consumers -> Primary Producers -> Note how the total amount of energy (Kcal/m2/yr) available at each higher level decreases...
14 Tropical Rain Forest Biomass PyramidNotice that the total producer biomass (mass of biologic material) is tremendously large. There is also a significant decomposer biomass because nutrients are recycled extremely fast in these kinds of ecosystems.
15 Humans Blue whale Sperm whale Crabeater seal Killer whale Elephant seal Leopard Adélie penguins Petrel Fish Squid Carnivorous plankton Krill Phytoplankton Herbivorous zooplankton Emperor penguin Antarctic Food Web Although highly simplified in this diagram, complex communities in ecosystems have high biodiversity with many species at the same trophic level.
16 Heat Tertiary consumers (human) Decomposers The loss of energy at each step up the trophic ladder produces a biomass pyramid in most ecosystems 10 Secondary consumers (perch) 100 Primary consumers (zooplankton) 1,000 10,000 Usable energy Available at Each tropic level (in kilocalories) Producers (phytoplankton)
17 tertiary consumer 1 cal secondary consumer 10 cal 100 calFigure: 29-07 Title: An energy pyramid for a prairie. Caption: The width of each rectangle is proportional to the energy stored at that trophic level. 100 cal primary consumer 1000 cal producer
18 How Do Materials Cycle Through The Earth System?Biogeochemical Cycling Cycling involves biological, geologic, and chemical factors. Three Main Categories Hydrologic Gaseous Sedimentary Hydrologic Cycle…The Important issues are... The quality of water available to humans The availability of water for human use The rate at which water flows through the cycle.
19 water vapor in atmosphere evaporation evaporation from land and fromtranspiration from plants evaporation from ocean precipitation over ocean precipitation over land Figure: 29-11 Title: The hydrologic cycle. Caption: water in ocean (reservoir) surface runoff groundwater seepage
20 Other Materials CyclesGaseous Cycles Exchanges among the atmosphere, biosphere, soils and oceans Most significant gaseous cycles include: Carbon Cycle Oxygen Cycle Nitrogen Cycle Sedimentary Cycles Involve materials that move from land to oceans and back Most significant sedimentary cycles include: Phosphorous cycle Sulfur cycle A few examples...
21 heat radiated into space sun outer space sunlight CO2 CFCs methanenitrous oxide atmosphere heat trapped in atmosphere volcano forest fires factories Figure: 29-15 Title: Increases in greenhouse gas emissions contribute to global warming. Caption: Incoming sunlight warms Earth’s surface and is radiated back to the atmosphere. Greenhouse gases absorb some of this radiated energy, trapping it in the atmosphere. vehicle emissions houses cows
22 Figure: 29-16 Title: Global warming parallels CO2 increases. Caption: The CO2 concentration of the atmosphere (blue line) has increased steadily since The dashed portion of that curve represents measurements made from air trapped in ice cores; the solid portion reflects direct measurements made at Mauna Loa, Hawaii. Average global temperatures (red line) show a parallel increase. (With thanks to Drs. Kevin Trenberth and Jim Hurrell of the National Center for Atmospheric Research.)
23 Nutrient cycling Greenhouse effectHuman interference with the carbon cycle Use of fossil fuels Global deforestation by burning Global warming 1) Potential consequences of global warming
24 The Nitrogen Cycle Soil Bacteria are the key to cycling nitrogen gas from the atmosphere to more useable forms such as ammonium and nitrate. It is estimated that human activities have at least doubled the rate at which nitrogen enters the worlds soils. How? Why?
25 Nutrient cycling Human impact on nutrient cycles Acid rainSulfuric and nitric acids as a result of overloading N and S cycles Acid rain examples 1) Adirondack Mountains—dead lakes 2) Mount Mitchell, N.C.—fog pH = 2.9