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01:119:115 (825)
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GENERAL BIOLOGY Notes (Part 18) - 4.0ed the course!

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Department
Biological Sciences
Course
01:119:115
Professor
A L L
Semester
Fall

Description
Ecosystem 12/06/2013 Ecosystem Sum of all organisms living in a given area + the abiotic factors that they interact with Regardless of size, dynamics involve 2 main processes: Energy flow (through ecosystems) Linear (one direction) Solar ▯ primary producers/autotrophs Always some loss of energy as heat during each transfer <1% solar energy trapped by photosynthetic organisms Energy will be transferred to decomposers Chemical cycling (within + through ecosystems) Chemicals/nutrients cycle back to primary producers Just like energy, matter cannot be created/destroyed Law of conservation of mass As result, we can measure how much of a chemical element recycles through ecosystem(s) Can measure how much carbon, nitrogen, phosphorus is gained/lost over time Easier to trace cycle/flow of matter & energy by grouping species into broad tropic levels Primary producers (autotrophs) ▯ primary consumers (heterotrophs) ▯ secondary consumers (heterotrophs)   ▯ tertiary consumers (heterotrophs) ▯ quaternary consumers (heterotrophs) Overview Energy flows Matter cycles Primary production Amount of light energy converted to chemical energy by autotrophs (in most ecosystems) Total photosynthetic production sets spending limit for whole ecosystem’s energy budget Total primary production Ecosystem’s gross primary production (GPP) Conversion of chemical energy from photosynthesis per unit time Net primary production (NPP) = GPP – Ra (energy used by primary producers for respiration) Energy per unit area per time (J/m^2*yr) Or Biomass added per unit area per time (g/m^2*yr) NPP is stored chemical energy for consumers; varies between ecosystems Net ecosystem production (NEP) Measure of total biomass accumulated (producers + consumers) per unit of time NEP = GPP –Rr (energy used by producers + consumers for respiration) Estimated by comparing net flux of CO2 + O2 in an ecosystem Useful as indicator of carbon storage or loss over time If more CO2 enters than leaves, system is storing carbon Both light + nutrients limit/control primary production in aquatic ecosystems Depth of light penetration affects primary production Nutrients limit primary production more than light Limiting nutrient – element that must be added for production to increase in an area N + P most often limit marine production, but other elements, too (e.g. iron) Upwelling – resurgence of nutrients from bottom of ocean by ocean currents Nutrient runoff can lean to eutrophication – too many nutrients in ecosystem; leads to an excess am
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