9unit13endangered species

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1、EndangeredspeciesTheSiberianTigerisasubspeciesoftigerthatiscriticallyendangered,3subspeciesoftigerarealreadyextinct.[1]ConservationstatusRiskofextinctionExtinctionExtinctExtinctintheWildThreatenedCriticallyEndangeredEndangeredVulnerableThreatenedLowerriskConse

2、rvationDependentNearThreatenedLeastConcernSeealsoWorldConservationUnionIUCNRedListAnendangeredspeciesisapopulationofanorganismwhichisatriskofbecomingextinctbecauseitiseitherfewinnumbers,orthreatenedbychangingenvironmentalorpredationparameters.Anendangeredspeci

3、esisusuallyataxonomicspecies,butmaybeanotherevolutionarysignificantunit.TheWorldConservationUnion(IUCN)hascalculatedthepercentageofendangeredspeciesas40percentofallorganismsbasedonthesampleofspeciesthathavebeenevaluatedthrough2006.[2](Note:theIUCNgroupsallthre

4、atenedspeciesfortheirsummarypurposes.)Manynationshavelawsofferingprotectiontothesespecies:forexample,forbiddinghunting,restrictinglanddevelopmentorcreatingpreserves.Onlyafewofthemanyspeciesatriskofextinctionactuallymakeittothelistsandobtainlegalprotection.Many

5、morespeciesbecomeextinct,orpotentiallywillbecomeextinct,withoutgainingpublicnotice.ConservationstatusTheconservationstatusofaspeciesisanindicatorofthelikelihoodofthatendangeredspeciesnotliving.Manyfactorsaretakenintoaccountwhenassessingtheconservationstatusofa

6、species;notsimplythenumberremaining,buttheoverallincreaseordecreaseinthepopulationovertime,breedingsuccessrates,knownthreats,andsoon.TheIUCNRedLististhebestknownconservationstatuslisting.Internationally,190countrieshavesignedanaccordagreeingtocreateBiodiversit

7、yActionPlanstoprotectendangeredandotherthreatenedspecies.IntheUnitedStatesthisplanisusuallycalledaspeciesRecoveryPlan.IUCNRedListEndangeredspeciesEndangeredspeciesundertheIUCNRedListreferstoaspecificcategoryofthreatenedspecies,andmayincludecriticallyendangered

8、species.IUCNRedListofThreatenedSpeciesusesthetermendangeredspeciesasaspecificcategoryofimperilment,ratherthanasageneralterm.UndertheIUCNCategoriesandCriteria,endangeredspeciesisbet