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BIOL 208 (March 31, 2014) - Efficiencies, Nutrient Cycling and Human Impact

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University of Alberta
Biology (Biological Sciences)
James Cahill

BIOL 208 (March 31, 2014) • Ecological efficiency (Lindeman’s efficiency) o % of energy transferred from one trophic level to the next o *E.E. = (exploitation) x (assimilation) x (production) o *Often around 10% • Assimilation efficiency o *A.E. = (Consumed energy assimilated)/(energy ingested) o *Herbivores have worse assimilation efficiency than carnivores  Some plants have toxins that are anti-nutritive (ex, tannin  bind to proteins to make them indigestible) • *Gross production efficiency o *G.P.E = (Production of mass)/(ingestion) o Endotherms 1-5%; ectotherms 5-30% • *Net production efficiency o *N.P.E. = (Production of mass)/(assimilation) o *Endotherms <5% (very little of what is consumed is converted into the animal that is eating… most is used for heat); Ectotherms <75% (ectotherms are extremely efficient at converting ingested energy to mass) o Energy that is taken out of food that goes toward growth or reproduction • Residence time: How long does it take for energy to move out of one trophic level? o *High? Once organic matter gets converted, it stays there for a VERY LONG time  Ex. rainforests (carbon stays for 20-some years) o *Low? = high organic matter turnover = little carbon sequestration  Ex. ocean and other aquatic habitats in general • Energy in biomass/NPP (net primary productivity) o = (standing biomass)/(biomass produced in a year) • *Longer residence = greater carbon sequestration • Nutrient Cycling o Overview of nutrient cycling; biogeochemical coupling  *Energy is essentially on a one-way trip through the ecosystem (energy flows through a system despite the presence of some energy recycling; energy is always leaving a system BUT energy is always entering a system as well)  *Many nutrients and elements are recycled though • *Nutrients reside in compartments (biotic or abiotic) o Ex. marine food web, or elements in solution o *Nutrients can move between compartments where the rate of this movement is called flux (the actual amount of nutrient that move from one compartment to another in a certain amount of time) • Not all nutrients are accounted for  we have n
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