选择性必修第二册配外研版Unit 5　Section A　Starting out Understanding ideas.pptx

;内容索引;素养导航;;WhyIsEcologicalBalanceImportant?

Ecosystemsareessential①toourwell-beingandprosperity②astheyprovideuswithfood,cleanairandfreshwater.Ecosystemsalsorepresentanexceptionalsourceofoutdoorrecreationopportunities.

Ecologicalbalanceisimportantforthecontinuedsurvivalandexistenceoforganismsaswellasthestabilityoftheenvironment.Thebalanceintheecosystem,whichmustbemaintained,maybedisturbedasaresultofnaturalhazards,theunexpecteddeathofaparticularspecies,man-madecausesortheintroductionofnewspeciestotheecosystem.?;Ecologicalbalanceisaconditionofadynamic③balancewithinanecosysteminwhichthespecies,geneticsandtheecosystemdiversityremaininastablestateirrespectiveofthegradualvariations④throughnaturalsuccession.Theecosystemstabilityischaracterizedbytwoproperties:resilienceandresistance.Resilienceisapropertythatismanifestedinanecosystemwhenorganismsarekilledorweakened.Resiliencealsoreferstotherateatwhichthedensityofapopulationinanecosystemcomesbacktotheequilibrium(平衡)afteraparticulardisturbance.Resistancestandsforthepotentialofanecosystemtopreventtheanimalpopulationandtreesfromgivingintostressessuchashighpollutionordrought.;Diversity⑤ismaintainedwhenorganismsinteract,andenhancingordestroyingaspecificspeciesinanecosystemmayaffecttheentirepopulationdensityovertime.Somespecies,suchastheseaotter(水獭),playasignificantroleinmaintainingecologicalbalanceandareknownaskeystonespecies.;词海拾贝

①essentialadj.基本的;必要的

②prosperityn.繁荣;成功

③dynamicadj.动态的

④variationn.变化;变异

⑤diversityn.多样性;典句欣赏

Thebalanceintheecosystem,whichmustbemaintained,maybedisturbedasaresultofnaturalhazards,theunexpecteddeathofaparticularspecies,man-madecausesortheintroductionofnewspeciestotheecosystem.

译文:我们必须维持的生态系统平衡可能会被自然灾害、某特定物种的意外死亡、人为原因或新的物种的引进等因素所毁坏。

分析:本句包含情态