3.3ThreatstoBiodiversity(Pages100-109)
LearningGoals
•Icanexplainhowbiodiversityisthreatenedbyhabitatloss,alienspecies,overexploitation,disruptingconnectivityacrossecosystemsandextinction.•Icanexplainhowbiodiversityisbeneficialtohumans.•Icansuggestwaystopreservebiodiversity.
KeyConcepts•Threatstobiodiversityincludehabitatloss,theintroductionofalienspecies,overexploitation,andbreakingtheconnectivityamongecosystems.•Deforestationanddrainingwetlandscanresultinhabitatloss.•VIDEO:ZebraMussels
KeyConcepts
•ExtinctionisanaturaleventthathasoccurredthroughoutEarth’shistory.•Currentextinctionratesmaybeacceleratedduetohumanactivities.
HabitatLoss
•HABITATLOSS:thedestructionofhabitats,whichusuallyresultsfromhumanactivities•Examples•Deforestation•DrainingWetlands
Deforestation•DEFORESTATION:thepracticeofclearingforestsforloggingorotherhumanuses,andneverreplantingthem
DrainingWetlands
•Wetlands:areasoflandthatarecoveredbywaterforpartoralloftheyear• Importantecosystemformanydifferentspecies•Coverabout14%ofCanada'stotallandarea
ImportanceofWetlands
AlienSpecies
•ALIENSPECIES:aspeciesthatisaccidentallyordeliberatelyintroducedintoanewlocation• INVASIVESPECIES:aspeciesthatcantakeoverthehabitat ofnativespecies•AliensHaveLandedI•AliensHaveLandedII
ZebraMussels:AnInvasiveSpecies
Zebramusselswereeatingmostoftheshrimp-likecrustaceanswhichareafoodsourceformanyfish,includingwhitefishandsmelt.Asthenumberofthesecrustaceanshasdeclined,sohavethenumbersofthesefish.Nativeclamsandmusselshaveexperiencedasignificantdeclineinnumbers,aszebramusselshaveoutcompetedwiththemforfood.
Practice
•Page109#1-8•Answerthefollowingquestions:
1. Whatisoverexploitation?2. Howcandisruptinganorganismthatexistsin
multipleecosystemseffectconnectivity?3. Whatisextinction?Whataresomecausesof
extinction?•Read“TheZebraMussel”handout• Socrative3.3miniquiz
Overexploitation•OVEREXPLOITATION: theuseorextractionofaresourceuntilitisdepleted•ThereducedcatchofAtlanticcodreflectsadecreaseinpopulationasaresultofoverexploitation
DisruptingConnectivityAcrossEcosystems
• Somespeciesareresponsibleforsustainingmultipleecosystems
Extinction
•EXTINCTION: thedeathofalltheindividualsofaspecies
•Backgroundextinctionà slow,steady,minorchanges•Massextinctionà sudden,rapid,majorchanges•Biodiversitycrisis:thecurrentacceleratedrateofextinctions
Somecausesofextinctionare:• Overhunting• Climatechange• Largemeteorimpacts• Disease• Invasivespecies• Urbansprawlandlossofhabitat
Thepassengerpigeon isanextinctNorthAmericanbird.ItwasoncethemostabundantbirdinNorthAmerica,andpossiblytheworld. ItaccountedformorethanaquarterofallbirdsinNorthAmerica.Thespecieslivedinenormousmigratoryflocksuntiltheearly20thcentury,whenhuntingandhabitatdestructionledtoitsdemise.
Oneflockin1866insouthernOntariowasdescribedasbeing1.5 kmwideand500 kmlong,took14hourstopass,andheldinexcessof3.5billionbirds.
Potentialde-extinctionSomehavesuggestedcloningthepassengerpigeoninthefuture.De-extinction effortsarenowunderwaytorevivethespeciesbyextractingDNAfragmentsfrompreservedspecimens,andlater,usingband-tailedpigeonsassurrogateparents.[
Practice
•Page109#1-8• Socrative3.3miniquiz• ProjectDUETHURSDAY(model),FRIDAY(writtenpiece)!