ECOLOGY FINAL STUDY GUIDE - ECOLOGY FINAL STUDY GUIDE...

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ECOLOGY FINAL STUDY GUIDENutrient CyclesNutrient pools and fluxesoPool: a compartment of nutrients containing a certain quantityEX. mg of nutrientoFlux rate: the rate of movement of nutrients between two compartments/ poolsEX. mg of nutrient per dayoInputs – outputs = storage of nutrientsoIn aquatic ecosystems, nutrients can actually get locked up in a single nutrient pool (in this case, sediments) and it restricts primary productionThe cycling of elements is a major aspect of how ecosystems functionoElement cycles interact with each otherEx. Acid rainoElements move through an ecosystem via different pathwaysoSources of elements:Air (nitrogen)Weathering of rocksThe majority of primary production in terrestrial ecosystems go into detritus communityGlobal nitrogen, sulfur, and water cyclesThe Nitrogen Cycle:Nitrogen Fixation:N2(from atmosphere) organic-NDone by plants and soil bacteriaAmmonification:Organic-N NH4+ (ammonia)Done by bacteria and fungiNitrificationNH4+NO3-(nitrate)Also produces NO (nitrogen oxide) and N2O (dinitrogen monoxide)Done by aerobic bacteriaDenitrificationNO3- N2(released back into atmosphere)Producing N2ODone by anaerobic bacteriaoPlants can only use NH4+and NO3- and sometime organic NoNitrogen is the limiting factor for tree growthSide Note: phosphorus in the limiting factor in freshwater ecosystemsoHumans have increased the amount of nitrogen in the atmosphere (it’s a greenhouse gas too)Lowers species diversityCan cause cancerEutrophication: excess nitrates in freshwater ecosystems causes major algae and phytoplankton growth causes problems for the rest of other species because sunlight is blockedLeads to low oxygen levels and poor water qualityCan lead to mass die-offs of fish and other species
The Sulfur Cycle:oFossil fuel burning has altered this cycle more than any otheroHumans produce 160% of normal atmospheric sulfur levelsoIncreases SO2(sulfur dioxide) which is further oxidized into sulfate (SO4 2-)oHas the power to affect ecosystems far away from the source of pollutionoCombines with water to form sulfuric acid (H2SO4)This is where acid rain comes from!Acid rain leaches nutrients from the soil and prevents rapid recoveryThe Water Cycle:oOnly 3% of the Earth’s water is freshwaterOf this almost 70% is trapped in glaciersoOur population is growing to a point where there might not be enough freshwater to provide for alloNitrogen creates an increase of zooplankton and algal. Their waste goes to the bottom of the water and takes up all the oxygen. The shortage of oxygen (hypoxia) causes animals to leave or die. oA way to combat this is to use less fertilizers Nitrogen, sulfur, and water cycling in terrestrial ecosystemsoDuring forest development, nutrients accumulate in leaves a woodoNitrogen:Major limiting factorThere’s no mineral source of it so it must be derived from the atmosphere

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