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EESA01 LEC 3.docx

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University of Toronto Scarborough
Environmental Science
Carl Mitchell

EESA01 LEC3 Sept24 Jennifer Wu Earth Systems, Ecosystem Ecology, and Global Biogeochemical Cycles What is a “System” SYSTEM INPUT OUTPUT “Open” Systems “Closed” Systems “Bomb” calorimeter Feedback Loops • It is possible for the output of a system to affect the input to that same system or to serve as the input to that same system. • This is a feedback loop. • Negative feedback loops: output from system becomes input to a system, moving that system in an opposite direction. • Positive feedback loops: output from system exacerbates the system response by moving it further toward one extreme. EESA01 LEC3 Sept24 Jennifer Wu Negative Feedbacks: Regulating Add: increasing temperatures, more cloud cover, less solar radiation input, lower temperatures. Positive Feedbacks: Devastating Equilibrium STEADY-STATE DYNAMIC Emergent properties are characteristics of a system not evident (perceivable) from its components alone or individually. In environmental science, the “system” that one might study has everything to do with the question being asked. EESA01 LEC3 Sept24 Jennifer Wu Major Earth Systems • Ecosystems • Hydrologic Cycle (next class) • Global Energy Balance (next class) • Biogeochemical Cycles: Carbon Cycle Nitrogen Cycle Phosphorus Cycle Sulphur Cycle Mercury Cycle and lots of others Systems Have Boundaries, but can Overlap if they are “Open” Ecosystems: A Broader Step Up From Community Ecology + abiotic world = ECOSYSTEM Ecosystem • All organisms and nonliving entities that occur and interact in a particular area at the same time Includes abiotic and biotic components Energy flows and matter cycles among these components Generally, the smallest ecologically “self-sufficient” space. EESA01 LEC3 Sept24 Jennifer Wu Ecosystem Structure • Energy entering the system is processed and transformed • Matter is recycled within ecosystem, resulting in outputs such as heat, water flow, and waste products Conversion of Energy to Biomass in Ecosystems • Principal source of energy? • Biomass: organic material that makes up living organisms. • Autotroph: an organism that produces complex organic compounds from sunlight and inorganic molecules (i.e., plants and some bacteria). • Gross Primary Production (GPP): Overall conversion of solar energy into chemical energy by autotrophs. • Respiration: metabolism. • Net Primary Productivity (NPP): Energy remaining after respiration, that goes toward accumulating biomass. • Net Ecosystem Productivity (NEP): NPP minus heterotrophic respiration and herbivory. Key Chemical Equations Photosynthesis occurs in the presence of light and chlorophyll: Respiration involves the use of accumulated carbon to produce needed energy (below is the aerobic process): NPP Across Ecosystems EESA01 LEC3 Sept24 Jennifer Wu NPP Across The Globe Factors Affecting NEP: 1. Nutrients • Nutrients (especially macronutrients like nitrogen and phosphorus) can be limiting factors for productivity. • Nitrogen usually limiting factor in marine systems, usually phosphorus in freshwater systems. 2. Oxygen Aerobic respiration: Energy Produced = 2872 kJ per mol glucose Examples of anaerobic respiration: Energy Produced = 2715 kJ per mol glucose C H O ®3CO +3CH 6 12 6 2 4 Energy Produced = 210 kJ per mol glucose Ecosystem Services EESA01 LE
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