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Lecture 17

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Biology (Sci)
BIOL 240
Christa Scholtz

• climate: average of atmospheric conditions (temp, precipitation, wind direction, velocity) found over long term [weather: short-term state of conditions] o vary in different parts of world due to solar energy • diff in air temp largely determined by solar energy input • rate at which solar energy arrives on Earth per unit of Earth’s surface depends on angle of sunlight o high latitudes (closer to poles) get less solar energy than equatorial places o higher latitudes have greater variation in day length and angle of arriving solar energy over year more seasonal variation in temp • air temp decreases with elevation o air rises, expands, pressure and temp dropmoisture released • global air circulation patterns result from global variation in solar energy input • intertropical convergence zone: the coming together of air masses. Air rises when it is heated by sun, so warm air rises in tropics, which receive greatest solar energy input. Rising air is replaced by air that flows in toward equator from N +S o heavy rains fall as rising air cools and releases moisture o shifts latitudinally with seasons, following zone of greatest energy input o can predict precipitation patterns in tropical and subtropical areas • air that replaces rising air in ICZ is replaced by air from aloft, that descends at 30 N and S latitudes after having travelled away from equator in atmosphere o air cooled+lost moisture while it rose to equator. Now, it descends, warms, takes up moisture ex. Sahara and Australian deserts • at poles (little solar energy), air descends; responsible for global wind patterns • spinning of earth on its axis also influences surface winds b/c earth’s velocity is rapid at equator, but relatively close to poles o stationary air mass’ velocity=earth’s velocity at same latitude o as air mass moves toward equator, meets a faster spin, and its rotational movement is slower than earth’s beneath it o air masses moving latitudinally are deflected to right in N hemisphere (NH) and to left in S hemisphere (SH)  those moving toward equator from N and S become northeast and south east trade winds respectively o air masses moving away from equator become westerly winds o air rises to pass over mountains, cools; clouds form on windward side of mountains and release moisture as rain/snow; on leeward side, dry air descends, warms, and again picks up moisturerain shadow = dry area • these global air circulation patterns drive circulation patterns of surface ocean waters: currents • trade winds cause water to converge at equator until encountering continental land mass; water splits so some moves north and south; transfers large amounts of heat at high latitudes o currents move towards poles, water veers right in NH and left in SH, and turns eastward until encountering another continent and is deflected laterally along shores o in NH +SH, water flows toward equator along western sides of continents • changes in env’t require immediate responses, some gradual (plants, lizards) • morphological+physiological features let organisms function in variable env’t • some anticipate changes so they mi
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