Bài giảng Biology - Chapter 50: An Introduction to Ecology and the Biosphere

Chapter 50An Introduction to Ecology and the BiosphereOverview: The Scope of EcologyEcologyIs the scientific study of the interactions between organisms and the environmentThese interactionsDetermine both the distribution of organisms and their abundanceEcologyIs an enormously complex and exciting area of biologyReveals the richness of the biosphereFigure 50.1Concept 50.1: Ecology is the study of interactions between organisms and the environmentEcologyHas a long history as a descriptive scienceIs also a rigorous experimental scienceEcology and Evolutionary BiologyEvents that occur in ecological timeAffect life on the scale of evolutionary timeOrganisms and the EnvironmentThe environment of any organism includesAbiotic, or nonliving componentsBiotic, or living componentsAll the organisms living in the environment, the biotaEnvironmental componentsAffect the distribution and abundance of organismsFigure 50.2Kangaroos/km2> 2010–205–101–50.1–1< 0.1Limits ofdistributionClimate in northern Australiais hot and wet, with seasonaldrought.Red kangaroosoccur in mostsemiarid and aridregions of theinterior, whereprecipitation isrelatively low andvariable fromyear to year.Southeastern Australiahas a wet, cool climate.Southern Australia hascool, moist winters andwarm, dry summers.TasmaniaEcologistsUse observations and experiments to test explanations for the distribution and abundance of speciesSubfields of EcologyOrganismal ecologyStudies how an organism’s structure, physiology, and (for animals) behavior meet the challenges posed by the environmentFigure 50.3a(a) Organismal ecology. How do humpback whales select their calving areas?Population ecologyConcentrates mainly on factors that affect how many individuals of a particular species live in an areaFigure 50.3bPopulation ecology.What environmentalfactors affect thereproductive rate ofdeer mice?(b)Community ecologyDeals with the whole array of interacting species in a communityFigure 50.3c(c) Community ecology.What factors influencethe diversity of speciesthat make up aparticular forest?Ecosystem ecologyEmphasizes energy flow and chemical cycling among the various biotic and abiotic componentsFigure 50.3d(d) Ecosystem ecology. Whatfactors control photosyntheticproductivity in a temperategrassland ecosystem?Landscape ecologyDeals with arrays of ecosystems and how they are arranged in a geographic regionFigure 50.3e(e) Landscape ecology. To what extent do the trees lining the drainage channels in this landscape serve as corridors of dispersal for forest animals?The biosphereIs the global ecosystem, the sum of all the planet’s ecosystemsEcology and Environmental IssuesEcologyProvides the scientific understanding underlying environmental issuesRachel CarsonIs credited with starting the modern environmental movementFigure 50.4Most ecologists follow the precautionary principle regarding environmental issuesThe precautionary principleBasically states that humans need to be concerned with how their actions affect the environmentConcept 50.2: Interactions between organisms and the environment limit the distribution of speciesEcologistsHave long recognized global and regional patterns of distribution of organisms within the biosphereMany naturalistsBegan to identify broad patterns of distribution by naming biogeographic realmsTropicof Cancer(23.5N)EquatorNearcticNeotropicalEthiopianOrientalAustralianPalearctic(23.5S)Tropic ofCapricornFigure 50.5BiogeographyProvides a good starting point for understanding what limits the geographic distribution of speciesFigure 50.6Species absentbecauseYesNoDispersallimitsdistribution?Behaviorlimitsdistribution?Biotic factors(other species)limitdistribution?Abiotic factorslimitdistribution?YesNoYesNoArea inaccessibleor insufficient timeHabitat selectionPredation, parasitism,competition, diseaseWaterOxygenSalinitypHSoil nutrients, etc.TemperatureLightSoil structureFireMoisture, etc.ChemicalfactorsPhysicalfactorsDispersal and DistributionDispersalIs the movement of individuals away from centers of high population density or from their area of originContributes to the global distribution of organismsNew areasoccupiedYear199619891974Natural Range ExpansionsNatural range expansionsShow the influence of dispersal on distributionFigure 50.7Species TransplantsSpecies transplantsInclude organisms that are intentionally or accidentally relocated from their original distributionCan often disrupt the communities or ecosystems to which they have been introducedBehavior and Habitat SelectionSome organismsDo not occupy all of their potential rangeSpecies distributionMay be limited by habitat selection behaviorBiotic FactorsBiotic factors that affect the distribution of organisms may includeInteractions with other speciesPredationCompetitionA specific case of an herbivore limiting distribution of a food speciesFigure 50.8 W. J. Fletcher tested the effects of two algae-eating animals, sea urchins and limpets, on seaweed abundance near Sydney, Australia. In areas adjacent to a control site, either the urchins, the limpets, or both were removed.EXPERIMENTRESULTS Fletcher observed a large difference in seaweed growth between areas with and without sea urchins.100806040200LimpetSeaurchinBoth limpetsand urchinsremovedOnlyurchinsremovedOnly limpets removedAugust1982February1983August1983February1984Control (bothurchins andlimpets present)Seaweed cover (%)Removing bothlimpets andurchins orremoving onlyurchins increasedseaweed coverdramatically.Almost noseaweed grewin areas whereboth urchins andlimpets werepresent, or whereonly limpets wereremoved. Removing both limpets and urchins resulted in the greatest increase of seaweed cover, indicating that bothspecies have some influence on seaweed distribution. But since removing only urchins greatly increased seaweed growth whileremoving only limpets had little effect, Fletcher concluded that sea urchins have a much greater effect than limpets in limitingseaweed distribution.CONCLUSIONAbiotic FactorsAbiotic factors that affect the distribution of organisms may includeTemperatureWaterSunlightWindRocks and soilTemperatureEnvironmental temperatureIs an important factor in the distribution of organisms because of its effects on biological processesWaterWater availability among habitatsIs another important factor in species distributionSunlightLight intensity and qualityCan affect photosynthesis in ecosystemsLight Is also important to the development and behavior of organisms sensitive to the photoperiodWindWindAmplifies the effects of temperature on organisms by increasing heat loss due to evaporation and convectionCan change the morphology of plantsFigure 50.9Rocks and SoilMany characteristics of soil limit the distribution of plants and thus the animals that feed upon themPhysical structurepHMineral compositionClimateFour major abiotic components make up climateTemperature, water, sunlight, and windClimateIs the prevailing weather conditions in a particular areaClimate patterns can be described on two scalesMacroclimate, patterns on the global, regional, and local levelMicroclimate, very fine patterns, such as those encountered by the community of organisms underneath a fallen logGlobal Climate PatternsEarth’s global climate patternsAre determined largely by the input of solar energy and the planet’s movement in spaceSunlight intensityPlays a major part in determining the Earth’s climate patternsFigure 50.10Low angle of incoming sunlightSunlight directly overheadLow angle of incoming sunlightNorth Pole60N30NTropic ofCancer0 (equator)30S60SAtmosphereLALITUDINAL VARIATION IN SUNLIGHT INTENSITYTropic ofCapricornSouth poleFigure 50.10June solstice: NorthernHemisphere tilts toward sun; summer begins in Northern Hemisphere; winter begins inSouthern Hemisphere.March equinox: Equator faces sun directly;neither pole tilts toward sun; all regions on Earthexperience 12 hours of daylight and 12 hours ofdarkness.60N30N0 (equator)30SConstant tiltof 23.5September equinox: Equator faces sun directly; neither pole tilts toward sun; all regions on Earth experience 12 hours ofdaylight and 12 hours of darkness.December solstice: NorthernHemisphere tilts away from sun; winter begins in Northern Hemisphere; summer begins in Southern Hemisphere.SEASONAL VARIATION IN SUNLIGHT INTENSITYDescendingdry airabsorbsmoistureAscendingmoist airreleasesmoistureDescendingdry airabsorbsmoisture3023.5023.530AridzoneTropicsAridzone60N30N0 (equator)30S60SGLOBAL AIR CIRCULATION AND PRECIPITATION PATTERNSAir circulation and wind patternsPlay major parts in determining the Earth’s climate patternsFigure 50.10GLOBAL WIND PATTERNSWesterliesNortheast tradesDoldrumsSoutheast tradesWesterliesAntarcticCircle60S30S0(equator)30N60NArcticCircleFigure 50.10Regional, Local, and Seasonal Effects on ClimateVarious features of the landscapeContribute to local variations in climateBodies of WaterOceans and their currents, and large lakesModerate the climate of nearby terrestrial environmentsFigure 50.11 Coolerair sinksover water.3 Air cools athigh elevation.21 Warm airover land rises.4 Cool air over watermoves inland, replacingrising warm air over land.Mountains have a significant effect onThe amount of sunlight reaching an areaLocal temperatureRainfallMountains Farther inland, precipitationincreases again as the airmoves up and over highermountains. Some of the world’sdeepest snow packs occur here.Figure 50.123 On the eastern side of theSierra Nevada, there is littleprecipitation. As a result ofthis rain shadow, much ofcentral Nevada is desert. As moist air moves inoff the Pacific Ocean andencounters the westernmostmountains, it flows upward,cools at higher altitudes,and drops a large amountof water. The world’s tallesttrees, the coastal redwoods,thrive here.12EastPacificOceanWinddirectionCoastRangeSierraNevadaSeasonalityThe angle of the sunLeads to many seasonal changes in local environmentsLakesAre sensitive to seasonal temperature changeExperience seasonal turnoverFigure 50.13In spring, as the sun melts the ice, the surface water warms to 4°Cand sinks below the cooler layers immediately below, eliminating thethermal stratification. Spring winds mix the water to great depth, bringing oxygen (O2) to the bottom waters (see graphs) andnutrients to the surface.2In winter, the coldest water in the lake (0°C) lies justbelow the surface ice; water is progressively warmer atdeeper levels of the lake, typically 4–5°C at the bottom.1In autumn, as surface water cools rapidly, it sinks below theunderlying layers, remixing the water until the surface beginsto freeze and the winter temperature profile is reestablished.4In summer, the lake regains a distinctive thermal profile, with warm surface water separated from cold bottom water by a narrowvertical zone of rapid temperature change, called a thermocline.3WinterSpringHighMediumLowO2 concentrationO2 (mg/L)Lake depth (m)048128162481624Lake depth (m)O2 (mg/L)O2 (mg/L)Lake depth (m)0481281624O2 (mg/L)Lake depth (m)0481281624AutumnSummer4C444444C444204C444444C681820225Thermocline04812MicroclimateMicroclimateIs determined by fine-scale differences in abiotic factorsLong-Term Climate ChangeOne way to predict future global climate changeIs to look back at the changes that occurred previouslyFigure 50.14Current rangePredictedrangeOverlap(a) 4.5C warming overnext century(b) 6.5C warming overnext centuryConcept 50.3: Abiotic and biotic factors influence the structure and dynamics of aquatic biomesVarying combinations of both biotic and abiotic factorsDetermine the nature of Earth’s many biomesBiomesAre the major types of ecological associations that occupy broad geographic regions of land or waterThe examination of biomes will begin with Earth’s aquatic biomesFigure 50.1530NTropic of CancerEquator30SContinentalshelfLakesCoral reefsRiversOceanic pelagiczoneEstuariesIntertidal zoneAbyssal zone(below oceanicpelagic zone)KeyTropic ofCapricornAquatic biomesAccount for the largest part of the biosphere in terms of areaCan contain fresh or salt waterOceansCover about 75% of Earth’s surfaceHave an enormous impact on the biosphereMany aquatic biomes Are stratified into zones or layers defined by light penetration, temperature, and depthMarine zonation. Like lakes, the marine environment is generally classified on the basis of light penetration (photic and aphotic zones), distance from shore and water depth (intertidal, neritic, and oceanic zones), and whether it is open water (pelagic zone) or bottom (benthic and abyssal zones).Zonation in a lake. The lake environment is generally classified on the basis of three physical criteria: light penetration (photic and aphotic zones), distance from shore and water depth (littoral and limnetic zones), and whether it is open water (pelagic zone) or bottom (benthic zone).(a)LittoralzoneLimneticzonePhoticzoneBenthiczoneAphoticzonePelagiczoneIntertidal zoneNeritic zoneOceanic zone0200 mContinentalshelfPhotic zonePelagic zoneAphoticzoneBenthiczone2,500–6,000 mAbyssal zone(deepest regions of ocean floor)(b)Figure 50.16a, bLakesFigure 50.17An oligotrophic lake in Grand Teton, Wyoming A eutrophic lake in Okavango delta, BotswanaLAKESWetlandsFigure 50.17WETLANDSOkefenokee National Wetland Reserve in GeorgiaStreams and riversSTREAMS AND RIVERSFigure 50.17A headwater stream in theGreat Smoky MountainsThe Mississippi River farform its headwatersEstuariesFigure 50.17An estuary in a low coastal plain of GeorgiaESTUARIESIntertidal zonesFigure 50.17INTERTIDAL ZONESRocky intertidal zone on the Oregon coastOceanic pelagic biomeFigure 50.17Open ocean off the island of HawaiiOCEANIC PELAGIC BIOMECoral reefsFigure 50.17A coral reef in the Red SeaCORAL REEFSMarine benthic zoneFigure 50.17A deep-sea hydrothermal vent communityMARINE BENTHIC ZONEConcept 50.4: Climate largely determines the distribution and structure of terrestrial biomesClimateIs particularly important in determining why particular terrestrial biomes are found in certain areasClimate and Terrestrial BiomesClimate has a great impact on the distribution of organisms, as seen on a climographFigure 50.18DesertTemperate grasslandTropical forestTemperatebroadleafforestConiferousforestArctic andalpinetundraAnnual mean precipitation (cm)Annual mean temperature (ºC)1002003004003015015The distribution of major terrestrial biomes30NTropic ofCancerEquatorTropic ofCapricorn30SKeyTropical forestSavannaDesertChaparralTemperate grasslandTemperate broadleaf forestConiferous forestTundraHigh mountainsPolar iceFigure 50.19General Features of Terrestrial BiomesTerrestrial biomesAre often named for major physical or climatic factors and for their predominant vegetationStratificationIs an important feature of terrestrial biomesTropical forestTROPICAL FORESTA tropical rain forest in BorneoFigure 50.20DesertFigure 50.20DESERTThe Sonoran Desert in southern ArizonaSavannaFigure 50.20SAVANNAA typical savanna in KenyaChaparralCHAPARRALAn area of chaparral in CaliforniaFigure 50.20Temperate grasslandSheyenne National Grassland in North DakotaFigure 50.20TEMPERATE GRASSLANDConiferous forestFigure 50.20Rocky Mountain National Park in ColoradoCONIFEROUS FORESTTemperate broadleaf forestFigure 50.20TEMPERATE BROADLEAF FORESTGreat Smoky Mountains National Park in North CarolinaTundraFigure 50.20TUNDRADenali National Park, Alaska, in autumn