可汗阅读30篇（新增）天道教育可汗阅读23篇（新增）天道教育http://tiandaoedu.com/Level2Passage41Level2Passage54Level2Passage67Level2Passage710Level3Passage613Level3Passage716Level4Passage419Level4Passage522Level4Passage625Level4Passage728Level2Passage231Level2Passage334Level2Passage437Level3Passage440Level4Passage343Level2Passage546Level2Passage649Level3Passage452Level3Passage555Level4Passage358Level2Passage461Level2Passage564Level3Passage567Part1SciencePart2SocialSciencePart3HistoryPart4Literature天道教育http://tiandaoedu.com/CONTINUE1ScienceQuestions1-11arebasedonthefollowingpassage.ThispassageisexcerptedfromDavidB.WakeandVanceT.Vredenburg,“AmphibiansinCrisis.”©2008byTheNationalAcademyofSciencesoftheUSA.Amphibianshavereceivedmuchattentionduringthelastdecadesbecauseofanow-generalunderstandingthatalargerproportionofamphibianspeciesareatariskofextinctionthanthoseofanyothertaxon.*Whythisshouldbehasperplexedamphibianspecialists.Alargenumberoffactorshavebeenimplicated,includingmostprominentlyhabitatdestructionandepidemicsofinfectiousdiseases;globalwarmingalsohasbeeninvokedasacontributingfactor.Whatmakestheamphibiancasesocompellingisthefactthatamphibiansarelong-termsurvivorsthathavepersistedthroughthelastfourmassextinctions.Paradoxically,althoughamphibianshaveproventhemselvestobesurvivorsinthepast,therearereasonsforthinkingthattheymightbevulnerabletocurrentenvironmentalchallengesand,hence,serveasmultipurposesentinelsofenvironmentalhealth.Thetypicallifecycleofafroginvolvesaquaticdevelopmentofeggsandlarvaeandterrestrialactivityasadults,thusexposingthemtoawiderangeofenvironments.Froglarvaearetypicallyherbivores,whereasadultsarecarnivores,thusexposingthemtoawidediversityoffood,predators,andparasites.Amphibianshavemoistskin,andcutaneousrespirationismoreimportantthanrespirationbylungs.Themoist,wellvascularizedskinplacestheminintimatecontactwiththeirenvironment.Onemightexpectthemtobevulnerabletochangesinwaterorairqualityresultingfromdiversepollutants.Amphibiansarethermal-con...
