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evolutionary ecology.
focuses on adaptations of indivduals within a population
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population ecology.
focuses on demography and simple interactions (within a population or between two populations)
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community ecology.
- focuses on complex species interactions.
- (eg. indirect effects of food webs and succession)
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ecosystem ecology.
- focus on complex interactions among all species and physical environment
- -according to pathways of energy, matter, and information.
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ecosystem perspective.
- -traces pathway of matter and energy flow
- -principles of feedback dynamics to understand regulatory pathways and state in the system
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energy flow
major energy transformations majorly depend on photosynthesis or respiration.
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photosynthesis.
photosynthesis and plant growth turns carbon dioxide and water into organic carbon. stores energy
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respiration.
by plants and animals, organic carbon is broken down into carbon dioxide and water. releases energy that does work and degrades into heat.
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energy transformations based on trophic levels.
- energy flows thru paths in food web, cuz energy is stored and transferred in biomass.
- -energy is lost at each transfer
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ecosystem functions and nutrients.
- P - phosphorous
- C - carbon
- N - nitrogen.
- -required for growth, maintenance, and reproduction of organisms.
- -cycling of each element is a major functions of ecosystems.
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Phosphorous...
- occurs in mineral deposits and marine sediments
- -released thru weathering of rock
- -assimilate thru plants and recycled thru ecosystem
- -unassimilated P washed into oceans, where remains dissolved till deposited into sediments
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nitrogen. cycle of this summarized by 4 chemical transformations.
- 1. fixation.
- 2. ammonification
- 3. nitrificaton.
- 4. denitrification.
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fixation of nitrogen.
speclized bacteria reduce atmospheric nitrogen to biologically useful forms with enzyme nitrogenase either ammonium or as nitrate.
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ammonificaton.
organic nitrogen compounds used by plants to construct proteins. proteins eventually metabolized and excess nitrogen is excreted to environment as waste.
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nitrification.
ammonia excreted as waste can further metabolized by microbes in soil. the oxidation of ammonia to nitrite, from mitrite to nitrate.
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denitrification.
in soil under anaerobic conditions, microbes convert nitrates back to N gas.
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Carbon.
foundation of all organic molecules. atmospheric C compounds such as carbon dioxide and methane influence global climate.
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3 classes of processes cause carbon to cycle thru ecosystems.
- 1. photosynthesis/respiration
- 2. exchange of CO2 between atmosphere and oceans.
- 3. precipitation of carbonate sediments in oceans
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links between N and C cycles.
- dependent on global distribution of land cover:
- -photosynthesis requires N.
- -N limiting in most ecosystems.
- -fixation and storage of C closely linked to N cycle
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as vegetation develops..
soil nitrogen content tends to increase, organic carbon content increase, fraction of phosphorous available decreases
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distrubance increases.. and...
nutrient losses from ecosystems
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effects of excess nutrients.
- disrupt ecosystem function and structure.
- -terrestrial ecosystems, lead to reduced species richness, simplified community structure
- -favor few competitively dominant species
- -aquatic evironment: can come from human and natural sources.
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effects of excess of nutrients in aquatic environments..
- population booms and death of primary producers = huge detritus inputs. decomposition of dead organisms strips waters of oxgyen.
- -extreme: water can become hypoxic
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