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Ecology Lec 3 (physical environment) summary.docx

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Western University
Biology 2483A
Hugh Henry

Ecology Lec 2: The physical environment Potential causes of salmon declines - dam construction- can’t come back to lay eggs - Saw osscilations with climate - sediment from logging - Saw opposite trends in different - water pollution - overharvesting altitudes Physical environment- determines where organisms can live & what resources are available Weather: current conditions- temp., precipitation, humidity, cloud cover (hot this week compared to same week last year is because of weather) Climate: long term description of weather, based on averages, measured over decades (hot this time of the year- expected because of climate) Long term climate change - changes in intensity & distribution of sun’s radiation Current climate changes - because of increased CO etc2in atmosphere due to humans Climate determines geographic distribution of organisms - Sun = ultimate source of energy → drives global climate system - Energy gains from sun = Energy losses … then Earth’s temp remains stable Solar radiation coming in = 50% absorbed by surface + 20% absorbed by atmos. + 30% reflected Greenhouse gases- bounce back IR radiation (e.g. H2O, CO2, CH4, N2O) - without them = 33 cooler… therefore need them Latitudinal differences in solar radiation: - Equator: same E. spread over small area & less atmos. to go through - Poles: same E. spread over large area & more atmos. to go through Solar radiation → heats earth surface which emits IR → heats air above it → uplift (less dense warm air rises) → air pressure decreases with altitude → rising air expands & cools (clouds formed) ↑ solar radiation = ↑ precipitation Equator- uplift, low pressure, reaches tropo-strato boundary, flows to the poles 3 cells = 3 major climatic zones in each hemisphere 1. Polar 2. Temperate 3. Tropical Prevailing winds (from west) because of Coriolis effect Water- high heat capacity ∴ oceans are moderate Semi-permanent high-low pressure cells: Summer- air over oceans is cooler/denser ∴ high pressure over oceans (low pressure on land) Winter- air over continents is cooler/denser ∴ high pressure over land (low pressure on oceans) Ocean currents driven by wind currents (ocean is 2
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