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Lecture 3

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University of Toronto Scarborough
Biological Sciences
Marc Cadotte

BIOB50Winter2012 Lecture 3Chapter 2Chapter 3 Organisms and Their Environment Global Diversity o The physical environment ultimately determines where organisms can live and the resources that are available to themunderstanding the physical environment is key to understanding ecological phenomenao Example you will not find Nemo in the dessert because he CANNOT survive there o Across the world there is a similar pattern in the places that have a high number of species of animalsalso have a high number of species of plants Latin America and Africa and some SEastern part of North America o This pattern is driven by climate Climateo Climate is the most fundamental characteristic of the physical environmento Weather the current temperature humidity precipitation wind and cloud cover o Climate long term description of weather based on averages and variations measured of decades temperature wind and precipitation o Longerterm climate change occurs as a result of changes in the intensity and distribution of solar radiation reaching the earths surface o Currently the earths climate is changing because of the greenhouse gas effect gases absorb and radiate energy back to the earths surface warming itexample not many species found in o Climate determines the geographic distribution of organismsnorthern Asia because it is too cold o Example record high temperaturesa severe drought caused widespread mortality in large stands of pinon pines in SW USAphysical environment must also be characterized by its variability over time not just the average conditionsthese extreme events can cause largescale mortality of vegetation o Example the blue jay lives in the eastern part of North America and not too far north because northtoo cold and westtoo dryo Climate also influences the rates of abiotic processes that affect organismsexample rate at which rocks and soil are broken down to supply nutrients to plants and microorganismso Climate also influences periodic disturbances such as fires and rockslideskill and destruct but also create opportunities for the establishment and growth of new organisms and communities Atmospheric and Oceanic Circulation o Solar radiation from the Sun come horizontally but because earth is tilted the energy has to be dissipated over a greater area at the North Pole than at the Equator where it hits straight at 90 degrees to the planet 1oo Also the amount of atmosphere the rays must pass through increases towards the poles so more radiation is reflected and absorbed before it reaches the surfaceestablishes latitudinal gradients in temperatureo The earth being tilted as well as moving around the sun causes seasons on Earthchanges in the amount of solar radiation received at any location over the course of the yearAtmospheric Circulation Cells in Regular Latitudinal Patternso Heating the earths surface varies with latitude and with topographycreates pockets of warm air surrounded by cooler airo Uplift process where the warm air as long as it remains warmer than the surrounding air it will riseo Atmospheric pressure results from the force exerted on a packet of air by the air molecules above it it decreases with increasing latitude o As the warm air rises it expands which cools the rising aircannot contains as much water vapour so it begins to condense into droplets and forms cloudsform of latent heat transfer o The clouds rise until they reach the boundary between the troposphere and the stratosphere warmer temperatures cause it to stop rising o2
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