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BIO120H1 (305)
Chapter 2

Chapters 2+3 - Lecture 3 - Week 2.docx

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University of Toronto St. George
Michelle Hilscher

Lecture 3 BIOB50 Chapters 2The Physical EnvironmentClimatic Variation and Salmon Abundance A Case StudyGrizzly bears of the Pacific Northwest feed on salmon seasonally when they arrive in the freshwater streamsSalmon are anadromous born in freshwater streams live as adults in ocean return back to the freshwater streamsSalmon was in the diet of Native Americans Commercial salmon fishing is risky successful salmon reproduction depends on the health of the streams Salmon declines due toConstruction of damsIncreases in stream sediments due to logging operations water pollution overharvestingResearchers primarily looked at the freshwater streams as the problem however it was suggested that it may be the marine env where they spend most of their adult lifeHigh salmon production in one area and low in the other link between multidecadal shifts and salmon and changes in sea surface temperature in the North Pacific Abrupt changes in salmon productionIntroductionPhysical environment determines if organisms will live there the resources available the rate at which their population can growIt includes climate long term trends of wind precipitation and temperatureRadiation from the sun drives the climate system and biological energy productionIncludes the chemical environment Salinity concentration of dissolved saltsAcidity pHConcentrations of gases in the atmosphere and water Soil is importantmicroorganisms plants animals live in and influences availability of resources such as water and nutrients ClimateWeather current temperature humidity precipitation wind cloud cover Climate long term description of weather at a given location based on averages and variation measured over decades Climatic variation includes Daily and seasonal cycles associated with changes in solar radiation as the Earth rotates on its axis and around the sun Changes over years or decades such as largescale cyclic weather patterns related to changes in the atmosphere and oceans Longerterm climate changes are a result of the changes associated with the amount of solar radiation reaching Earth Climate Controls Where and How Organisms LiveClimate determines where an organism lives geographic distribution and how they functionTemperature determines the rates of biochemical reactions and physiological activityWe characterize any aspect of the physical environment ex climate at a given location by the average of the conditions over timeThe physical environment is also characterized by its variability over timeThe timing of the changes in a physical environment is also ecologically importantClimate also determines the rate of abiotic processes ex rate at which soil and rocks are broken down to supply nutrientsClimate also influences the rates of periodic disturbances that wipe out organisms but create opportunities for new organisms and communities Global Energy Balance Drives the Climate SystemEnergy that drives the global climate is derived from solar radiation
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