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BIOL 1020

Ch 52: Ecology and the Distribution of Life 52.1 • ecology: scientific study of rich and varied interactions btwn organisms and environment • communities: systems embracing all the organisms loving together in the same area • ecosystems: systems embracing all organisms in an area plus their physical environment • environment: encompasses abiotic (physical+chemical ex water, minerals) and biotic (living organisms) factors • interactions btwn organisms and environment are 2 way processes: o organisms both influence and are influenced by environment • understanding ecology allows us to manage ecosystems, to grow food, control pests, deal with natural disasters, etc • ecologists become familiar with various environments and understand how organisms adapt to them 52.2 • 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 migrate or enter resting state (hibernation) before adverse conditions come • most changes in physical environment happen independently of anything organisms do; others influenced by activities or organisms 52.3 • biome: terrestrial environment defined by grown forms of plants (forests, tundra) o plant distribution influenced by temp and rainfall o one set of graphs plots seasonal patterns of temp and precipitation at a site in a biome o some graphs show activity patterns of different kinds of organisms / year; levels of biological activity shown by width of horizontal bars o species richness: number of species present in communities • boundary btwn biomes is arbitrary; gradually merge into another • tundra biome: arctic and high elevations in mountains everywhere o in Arctic t, vegetation is underlain by permafrost—soil who water is permanently frozen; soil may thaw in short summer  little precipitation but very wet b/c water can NOT drain through permafrost  plant grow for few months/year  animals migrate into area for summer or are dormant for most of year o tropical alpine t: photosynthesis and most bio activities continue (slowly)  more plant forms present • boreal forest: toward equator from Arctic t, lower elevations on mountains o winders long and cold, summers short, warm o evergreen tress b/c ready to photosynthesize as soon as it gets warm o NH: has evergreen coniferous gymnosperms; SH: southern beeches o Temperate evergreen forests: grow along western coasts of continents at middle to high latitudes; winters mind and wet, summers cool and dry; earth’s tallest trees o few tree species; moose, hares; seeds of conifersrodents, birds, insects • temperate deciduous forest: eastern NA, eastern Asia, Europe o temps fluctuate btwn winter and summer, precipitation evenly distributed o deciduous trees dominate; more tree species than boreal o many genera or plants+animals shared in those 3 separate regions • temperate grassland: areas dry for much of year o hot summers, cold winters; converted to agriculture o in some, most precipitation falls in water, others in summer o vegetation = simple – perennial grasses, sedges, forbs (colourful) o plants adapted to grazing and fire; store energy underground and resprout • cold desert: dry regions at middle to high latitudes; esp in continents in rain shadows of mountain ranges o seasonal temp changes great; dominated by few species of low-growing shrubs; annual productivity is low b/c soils dry rapidly in spring o surface of soil recharged w/ moisture in winter, plant growth concentrated in spring o poor in species of most taxonomic groups, but lots of seeded plantssupports seed- eating animals o • hot desert: two belts – 30 N and S – where air descends, warms, picks up moisture o scarce rainfall in summer, winter rains from ocean storms o richer, structurally more diverse vegetation (cacti) o annual plants germinate+ abundantly grow; pollination+dispersal of fruits o rodents, termites, ants, lizards, snakes • chaparral: western sides of continents, mid-latitude, cool ocean currents flow off-shore o cool, wet winters; warm, dry summers o dominant plants: low growing shrubs and trees with tough evergreen leaves o annual plants abundant, produce seeds that fall into soil small rodents o vegetation is naturally adapted to survive periodic fires • thorn forest: equatorial sides of hot deserts o climate: semiarid – little rain in winter, heavy rain in summe
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