完整版环境科学交叉关系学科56章重点句词汇.docx
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完整版环境科学交叉关系学科56章重点句词汇
第五章环境和生物间的相互作用Interactions:
EnvironmentsandOrganisms
Thescienceofecologyisthestudyofthewaysorganismsinteractwitheachother,andwiththeirnonlivingsurroundings.
Ecologydealswiththewaysinwhichorganismsareadaptedtotheirsurroundings,howtheymakeuseofthesesurroundings,andhowanareaisalteredbythepresenceandactivitiesoforganisms.
Allorganismsaredependentonotherorganismsinsomeway.
Everythingthataffectsanorganismduringitslifetimeiscollectivelyknownasitsenvironment.
Abioticfactorscanbeorganizedintoseveralbroadcategories:
energy,nonlivingmatter,andprocessesthatinvolvetheinteractionsofnonlivingmatterandenergy.
Allorganismsrequireasourceofenergytomaintainthemselves.Theultimatesourceofenergyforalmostallorganismsisthesun.
Allformsofliferequireatomsofelementssuchascarbon,nitrogen,andphosphorus,andmoleculessuchaswatertoconstructandmaintainthemselves.
Organismsconstantlyobtainthesematerialsfromtheirenvironment.Theatomsbecomepartofanorganism'sbodystructureforashorttimeperiod,andeventuallyallofthemarereturnedtotheenvironmentthroughrespiration,excretion,ordeathanddecay.
Thestructureandlocationofthespaceorganismsinhabitisalsoanimportantabioticaspectoftheirenvironment.
Importantecologicalprocessesinvolveinteractionsofmatterandenergy.
Theclimate(averageweatherpatternsoveranumberofyears)ofanareainvolvesenergyintheformofsolarradiationinteractingwiththematterthatmakesuptheEarth.
Thebioticfactorsofanorganism'senvironmentincludeallformsoflifewithwhichitinteracts.
Althoughorganismsinteractwiththeirsurroundingsinmanyways,certainfactorsmaybecriticaltoaparticularspecies'success.Ashortageorabsenceofthisfactorrestrictsthesuccessofthespecies;thus,itisknownasalimitingfactor.
Thelimitingfactorformanyspeciesoffishesistheamountofdissolvedoxygeninthewater.
Theenvironmentinfluencestheorganism,andorganismsaffecttheenvironment.
Thehabitatofanorganismisthespacethattheorganisminhabits,theplacewhereitlives(itsaddress).
Thenicheofanorganismisthefunctionalroleithasinitssurroundings(itsprofession).
GenesaredistinctpiecesofDNAthatdeterminethecharacteristicsanindividualdisplays.
Apopulationisconsideredtobealltheorganismsofthesamekindfoundwithinaspecificgeographicregion.
Aspeciesisapopulationofalltheorgantismspotentiallycapableofreproducingnaturallyamongthemselvesandhavingoffspringthatalsoreproduce.
Theprocessthatleadstothisclosefitbetweenthecharacteristicsorganismsdisplayandthedemandsoftheirenvironmentisknownasnaturalselection.
naturalselectionisthemechanismthatcausesevolutiontooccur.
Whenwelookattheeffectsofnaturalselectionovertime,wecanseeconsiderablechangeinthecharacteristicsofaspeciesandkindsofspeciespresent.Somechangestakethousandsormillionsofyearstooccur.Others,suchasresistancetopesticides,canoccurinafewyears.
Scientistshavecontinuouslyshownthatthistheoryofnaturalselectioncanexplainthedevelopmentofmostaspectsofthestructure,function,andbehavioroforganisms.Itisthecentralideathathelpsexplainhowspeciesadapttotheirsurroundings.Whenwediscussenvironmentalproblems,itishelpfultounderstandthatspecieschangeandthatastheenvironmentischanged,eithernaturallyorbyhumanaction,somespecieswilladapttothenewconditionswhileotherswillnot.
Theenvironmentinwhichorganismsexistdoesnotremainconstantoverlongtimeperiods.Thosespeciesthatlackthegeneticresourcestocopewithachangingenvironmentgoextinct.Extinctionisthelossofanentirespeciesandisacommonfeatureoftheevolutionoforganisms.
Naturalselectionisconstantlyatworkshapingorganismstofitachangingenvironment.
Itisclearthathumanshavehadasignificantimpactontheextinctionofmanykindsofspecies.
Whereverhumanshavemodifiedtheenvironmentfortheirpurposes(farming,forestry,cities,hunting,andintroducingexoticorganisms),speciesaretypicallydisplacedfromthearea.Iflargeareasaremodified,entirespeciesmaybedisplaced.Ultimately,humansarealsosubjecttoevolutionandthepossibilityofextinctionaswell.
Coevolutionistheconceptthattwoormorespeciesoforganismscanreciprocallyinfluencetheevolutionarydirectionoftheother.Inotherwords,organismsaffecttheevolutionofotherorganisms.Sinceallorganismsareinfluencedbyotherorganisms,thisisacommonpattern.
Ecologistslookatorganismsandhowtheyinteractwiththeirsurroundings.
Onecommonkindofinteractioncalledpredationoccurswhenoneorganism,knownasapredator,killsandeatsanother,knownastheprey.
Asecondtypeofinteractionbetweenspeciesiscompetition,inwhichtwoorganismsstrivetoobtainthesamelimitedresource.
Symbiosisisaclose,long-lasting,physicalrelationshipbetweentwodifferentspecies.Therearethreedifferentcategoriesofsymbioticrelationships:
parasitism,commensalism,andmutualism.
Ifweexamineouractivities,wecanseethatwehavecomplicatedinteractionswithotherorganisms.
Predator----Humansthroughouttheworlduseanimalsasfood.
Herbivore----Humansrelyonmanykindsofplantsastheirprimarysourceoffood.
Scavenger----Scavenginginvolvesfindingandconsuminganimalsthatarealreadydead.
Commensalism-----Humansfindthemselvesonbothsidesofcommensalrelationships.
Parasitism----Althoughhumansdonotliveinoronotherlivingthings,wedoengageinrelationshipsthatareparasiticinnature.
Mutualism----Humanshavemanymutualisticrelationshipswithplantsandanimals.
Competition----HumansareincompetitionwithallotherorganismsonEarth.Asweconvertlandandaquaticresourcestoouruses,wedepriveotherorganismsofwhattheyneedtosurvive.
Acommunityisanassemblageofalltheinteractingpopulationsofdifferentspeciesoforganismsinanarea.
Anecosystemisadefinedspaceinwhichinteractionstakeplacebetweenacommunity,withallitscomplexinterrelationships,andthephysicalenvironment.
Whileitiseasytoseethatthephysicalenvironmentplaceslimitationsonthekindsoforganismsthatcanliveinanarea,itisalsoimportanttorecognizethatorganismsimpacttheirphysicalsurroundings.
Everysystemhaspartsthatarerelatedtooneanotherinspecificways.
Producersareorganismsthatareabletousesourcesofenergytomakecomplex,organicmoleculesfromthesimpleinorganicsubstancesintheirenvironment.
Primaryconsumers,alsoknownasherbivores,areanimalsthateatproducers(plantsorphytoplankton)asasourceoffood.
Secondaryconsumersorcarnivoresareanimalsthateatotheranimals.
Decomposersareorganismsthatusenonlivingorganicmatterasasourceofenergyandrawmaterialstobuildtheirbodies.
Wheneveranorganismshedsapartofitself,excreteswasteproducts,ordies,itprovidesasourceoffoodfordecomposers.
Sincedecomposerscarryonrespiration,theyareextremelyimportantinrecyclingmatterbyconvertingorganicmattertoinorganicmaterial.
Manysmallanimals,fungi,andbacteriafillthisniche.
Akeystonespeciesisonethathasacriticalroletoplayinthemaintenanceofspecificecosystems.
Somespecieshavepivotalroles,andtheireliminationorseverereductioncansignificantlyalterecosystems.
Theenergystoredinthemoleculesofproducersistransferredtootherorganismswhentheproducersareeaten.Eachstepintheflowofenergythroughanecosystemisknownasatrophiclevel.Producers(plants,algae,phytoplankton)constitutethefirsttrophiclevel,andherbivoresconstitutethesecondtrophiclevel.Carnivoresthateatherbivoresarethethir,trophiclevel,andcarnivoresthateatother".carnivoresarethefourthtrophiclevel.
Asenergyflowsthroughanecosystem,itpassesthroughseverallevelsknownastrophiclevels.Eachtrophiclevelcontainsacertainamountofenergy.Eachtimeenergyflowstoanothertrophiclevel,approximately90percentoftheusefulenergyislost,usuallyasheattothesurroundings.Therefore,inmostecosystems,highertrophiclevelscontainlessenergyandfewerorganisms.
Thepassageofenergyfromonetrophicleveltothenextasaresultofoneorganismconsuminganotherisknownasafoodchain.
Whenseveralfoodchainsoverlapandintersect,theymakeupafoodweb.
Allmatterismadeupofatoms.Theseatomsarecycledbetweenthelivingandnonlivingportionsofanecosystem.Theactivitiesinvolvedinthecyclingofatomsincludebiological,geological,andchemicalprocesses.Therefore,thesenutrientcyclesareoftencalledbiogeochemicalcycles.
Alllivingthingsarecomposedoforganicmoleculesthatcontainatomsoftheelementcarbon.Thecarboncycleincludestheprocessesandpathwaysinvolvedincapturinginorganiccarbon-containingmolecules,convertingthemintoorganicmoleculesthatareusedbyorganisms,andtheultimatereleaseofinorganiccarbonmoleculesbacktotheabioticenvironment.
Fossilfuels(coal,oil,andnaturalgas)arepartofthecarboncycleaswell.
Atonetime,thesematerialswereorganicmoleculesinthebodiesoflivingorganisms.
Theorganismswereburiedandtheorganiccompoundsintheirbodiesweremodifiedbygeologicforces.Thus,thecarbonatomspresentinfossilfuelswereremovedtemporarilyfromtheactive,short-termcarboncycle.Whenweburnfossilfuels,thecarbonreenterstheactivecarboncycle.A