Chapter 20 Notes
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This 0 page Class Notes was uploaded by Morgan Deal on Tuesday December 1, 2015. The Class Notes belongs to 301 at University of South Carolina taught by Dr. April South in Summer 2015. Since its upload, it has received 26 views. For similar materials see Ecology and Evolution in Biology at University of South Carolina.
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Date Created: 12/01/15
CHAPTER 20 Movement of Energy in Ecosystems Primary Productivity 0 Most energy originates as solar energy powers photosynthesis No sun available chemosynthesis 0 Deep ocean thermal vents Producers harness energy and form base of food web use energy for respiration growth and reproduction 0 Energy used for growth and reproduction is available for consumption 0 Primary productivity rate at which solarchemical energy is captured and converted into chemical bonds 0 How much energy is available in the ecosystem Standing crop biomass of producers present in an area at a moment in time 0 High primary productivity does NOT always equal high standing crop 0 Consumers 0 Gross primary productivity GPP rate at which energy is captured and assimilated by producers in an area 0 Net primary productivity NPP rate at which energy is captured assimilated and converted into producer biomass energy not respired o NPP GPP respiration 0 Measured in Joules Jmeters squaredyear Measuring o NPP can be measured as change in producer biomass over time Herbivory and tissue mortality underestimate NPP Harvest only above ground growth underestimate NPP Mutualisms with mycorrhizal fungi affects accuracy of NPP 0 Measuring carbon dioxide uptake and release Lightdark bottle experiment Carbon isotopes in carbon dioxide track movement Carbon dioxide monitoring towers Measuring oxygen uptake and release 0 Remote sensing allows measurement of conditions on earth from remote location using satellite Use of pigment wavelengths Much larger spatial scale 0 Secondary Production Herbivores consume only a fraction of total producer biomass available 0 Can only digest a portion of energy consumed Egested energy consumed energy excreted Assimilated energy energy digested and absorbed Respired energy energy respired Net secondary productivity energy used for growth and reproduction o Assimilated energy respired energy Productivity in Terrestrial Ecosystems o NPP is positively correlated with annual temperature generally 0 Tropical areas increased NPP 0 High latitudes limited NPP o Deserts limited NPP o NPP is positively correlated with annual precipitation until 3m is reached too much rainfall leeches nutrients and affects decomposition Nutrients can affect NPP nitrogen and phosphorus Productivity in Aquatic Systems Limited by temperature precipitation nutrients Also limited by light If similar light and temperature levels NPP limited by nutrients Nutrient limitation in ocean limited by other nutrients 0 Si diatoms 0 Fe combines with phosphorus and precipitates Adding Fe causes phytoplankton concentration to triple Problem with growth of algae and phytoplankton Reduction of carbon dioxide in air and ocean increase in respiration may counteract this Efficiencies of Energy Transfer 0 Consumption ef ciency energybiomass consumed by next higher trophic level consumed energy net production energy of next lower trophic level O Assimilation ef ciency consumed energy assimilated assimilated energy O Asimilation e iciency consumed energy 0 Primary consumers have lower assimilation efficiencies than secondary consumers Prey tissues are more digestible than plant tissue 0 Net production ef ciency assimilated energy used for growth and reproduction o remaining after respiration o Homeotherms have low poikilotherms have high 0 net production energy Net production e iciency assimilated energy Ecological ef ciency ef ciency with which energy is passed between trophic levels 0 0 net production energy of trophic level net production energy of next lower trophic level Incorporates consumption assimilation and net production 0 Low 10 is default value Number of Trophic Levels 0 Aquatic v terrestrial Differences in ecological ef ciencies O O O O Terrestrial plants contain defense compounds Terrestrial plants have tissues that can t be consumed Aquatic algae are easily consumed Consumers in aquatic systems are only slightly larger than their diet Residence Times energy present E trophic level L2 m Energy residence time J net productivity year Kg 2 net productivity year 0 Z K biomass present E trophic level Biomass residence time Z 0 Average residence times for primary producers Terrestrial gt20 years Aquatic lt20 years Energy and biomass residence times to not take dead organic matter into consideration Dead organic matter residence time years Kg 2 DOM productivity year 0 L K DOM present E trophic level 3 m a Stoichiometry Ecological stoichiometry how balance of energy is affected by organism reactions 0 Nutrient requirements depends on organism biology 0 Ratio of ingested nutrients to required is low consume more 0 More consumption more excretion lowering ecological ef ciency Trophic Pyramids 0 Chart representing amount of energy in each trophic group 0 total energy decreases as trophic level increases
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