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Ecosystem Energy FlowProductivity Studying organisms in their environment organism population community ecosystem biosphere Essential Questions: What limits the production in ecosystems? How do nutrients move in the ecosystem? How does energy move through the ecosystem? Ecosystem All the organisms in a community plus abiotic factors ecosystems are transformers of energy & processors of matter Ecosystems are self-sustaining what is needed? capture energy transfer energy cycle nutrients Ecosystem inputs constant energy flows input of through energy nutrients cycle Matter cannot Don’t forget laws of or bethe created Physics! destroyed nutrients can only cycle biosphere inputs energy nutrients Generalized Nutrient cycling consumers producers consumers decomposers nutrients nutrients ENTER FOOD CHAIN made available = made available to producers to producers Decomposition connects all trophic levels return to abiotic reservoir abiotic reservoir geologic processes Carbon cycle CO2 in atmosphere Combustion of fuels Industry and home Diffusion Respiration Photosynthesis Plants Animals Dissolved CO2 Bicarbonates Photosynthesis Animals Plants and algae Carbonates in sediment abiotic reservoir: CO2 in atmosphere enter food chain: photosynthesis = carbon fixation in Calvin cycle recycle: return to abiotic: respiration combustion Deposition of dead material Deposition of dead material Fossil fuels (oil, gas, coal) Nitrogen cycle abiotic reservoir: N in atmosphere enter food chain: nitrogen fixation by soil & aquatic bacteria recycle: decomposing & nitrifying bacteria return to abiotic: denitrifying bacteria Atmospheric nitrogen Carnivores Herbivores Birds Plankton with nitrogen-fixing bacteria Plants Death, excretion, feces Fish excretion Decomposing bacteria amino acids Ammonifying bacteria loss to deep sediments Nitrogen-fixing bacteria (plant roots) Nitrogen-fixing bacteria (soil) Nitrifying bacteria soil nitrates Denitrifying bacteria abiotic reservoir: rocks, minerals, soil enter food chain: erosion releases soluble phosphate uptake by plants recycle: decomposing bacteria & fungi return to abiotic: loss to ocean sediment Phosphorus cycle Plants Land animals Animal tissue Urine and feces Soluble soil phosphate Decomposers (bacteria and fungi) Loss in drainage Rocks and minerals Decomposers Phosphates (bacteria & fungi) in solution Animal tissue and feces Aquatic animals Plants and algae Precipitates Loss to deep sediment abiotic reservoir: surface & atmospheric water enter food chain: precipitation & plant uptake recycle: transpiration return to abiotic: evaporation & runoff Water cycle Solar energy Transpiration Water vapor Evaporation Precipitation Oceans Runoff Lakes Percolation in soil Groundwater Aquifer Transpiration Why does water flow into, up and out of a plant? We will discuss process in detail soon! Energy flows through ecosystems sun Energy is incorporated into a community by what group? secondary consumers (carnivores) primary consumers (herbivores) producers (plants) loss of energy loss of energy Ecosystem dynamics involve two main processes: energy flow (productivity) and chemical cycling (biogeochemical cycles) Energy flows through ecosystems Matter cycles within them Physical laws govern energy flow and chemical cycling in ecosystems Conservation of Energy (first law of thermodynamics) Energy enters from solar radiation and is lost as heat Conservation of matter - Chemical elements are continually recycled within ecosystems Ecosystems are open systems, absorbing energy and mass and releasing heat and waste products Productivity Primary productivity: Term for the rate which producers photosynthesize organic compounds in an ecosystem. Gross primary productivity: total amount of photosynthetic biomass production in an ecosystem Net Primary Productivity = GPP – respiration cost Ecosystems with greater productivity are more stable and diverse than ecosystems with less productivity. Which ecosystems are most productive? Energy transfer between trophic levels is typically only 10% efficient Net Primary Production (NPP) is the amount of new biomass added in a given time period Only NPP is available to consumers Ecosystems vary greatly in NPP and contribution to the total NPP on Earth Limited by light, nutrients and other abiotic factors Secondary is the amount of chemical energy in food converted to new biomass Inefficiency of energy transfer Loss of energy between levels of food chain To where is the energy lost? The cost of living! sun 17% growth only this energy moves on to the next level in the food chain energy lost to daily living 33% cellular respiration 50% waste (feces) Production Efficiency When a caterpillar feeds on a leaf, only about one-sixth of the leaf’s energy is used for secondary production An organism’s production efficiency is the fraction of energy stored in food that is not used for respiration Figure 55.10 Plant material eaten by caterpillar 200 J 67 J Feces 100 J Cellular respiration 33 J Not assimilated Growth (new biomass; secondary production) Assimilated Trophic Efficiency and Ecological Pyramids Trophic efficiency is the percentage of production transferred from one trophic level to the next It is usually about 10% (“10% Law”), with an actual range of 5% to 20% Trophic efficiency is multiplied over the length of a food chain sun Ecological pyramid Loss of energy between levels of food chain can feed fewer animals in each level 10% energy available for next level Notice only 1% of sunlight energy converted by plants Interesting Energy production facts: Birds and mammals have efficiencies in the range of 13% Fishes have production efficiencies of around 10% Insects and microorganisms have efficiencies of 40% or more WHY?? Role of Humans in Energy flow and nutrient cycling: Dynamics of energy flow in ecosystems have important implications for the human population Eating meat is a relatively inefficient in terms of utilizing photosynthetic production (and water) Worldwide agriculture could feed many more people if humans ate only plant material Fossil fuels used to produce foods Humans in food chains-carbon cycle Dynamics of energy through ecosystems have important implications for human populations How much energy does it take to feed a human? if we are meat eaters? if we are vegetarian? Better harvest? Combustion and water/ ocean pollution Humans and the water cycle Deforestation breaks the water cycle groundwater is not transpired to the atmosphere, so precipitation is not created forest desert desertification Effects of deforestation 40% increase in runoff loss of water loss into surface water 80 nitrate levels in runoff Concentration of nitrate (mg/l ) 60x loss in nitrogen 10x loss in calcium 40 loss out of ecosystem! 4 Deforestation 2 Why is 0 nitrogen 1965 so important? 1966 1967 Year 1968 What you need to be able to do: Using the laws of conservation of matter and energy to do some basic accounting and determine different aspects of energy and matter usage in a community. Remember: Inputs have to equal outputs Sample problem A caterpillar consumes 100 kcal of energy. It uses 35 kcal for cell respiration, and loses 50 kcal as waste. Determine the trophic efficiency for its creation of new biomass. Total energy = 100 kcal Lost and Respired: 35 + 50 = 85 kcal Total energy for growth: 15 kcal Efficiency = part/total = 15/100 = .15 (or 15% transfer or 3/20 as fraction) The “take home” energy defines ecology!