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KIDS CORNER
MASS EXTINCTION
Thisdocumentaimstoteachyouaboutmassextinction.
Thispresentationhasthefollowingstructure:
Slide1- WhatisMassExtinction?
Slide2- BigFiveMassExtinctions
Slide3- Ordovician-Silurian(EndOrdovician)
Slide4- LateDevonian
Slide5- Permian-Triassic(EndPermian)
Slide6- Triassic-Jurassic(EndTriassic)
Slide7- Cretaceous-Paleogene(EndCretaceous)
Slide8- Timeline
Slide9- TheSixthMassExtinction
Slide10- AustralianCurriculumMapping
KIDS CORNER
MASS EXTINCTION
WhatisMassExtinction?
Speciesbecomeextinctallthetime.You’veprobablyheardofanumberof
criticallyendangeredspecies,suchastheBorneanorangutanandthe
pangolin,thatcouldeasilybecomeextinctwithinyourlifetime.Aspecies
maybecomeextinctforanynumberofreasonsorcombinationsof
reasons,suchasoverhunting,disease,habitatdestruction,andsoon.
Amassextinctionisexactlywhatitsoundslike- extinctiononaverylarge
scale.When50%ormoreofallplantandanimalspeciesdisappearwithin
arelativelyshortperiodoftime,it’sreferredtoasamassextinction. Mass
extinctionsdramaticallyreduceEarth’sbiodiversity.Afteramass
extinction,theremainingspeciestendtodiversifyandfilltheecological
nichesleftvacantbytheextinctionofthespeciesthatformerlyfilled
them.
Scientistsusefossilrecordsandgeologicalevidencetotrytoidentifythe
mostlikelycausesofmassextinctions,suchasvolcaniceruptions,
asteroidimpacts,majorclimateshifts,andchangingsealevels.
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BigFiveMassExtinctions
ScientistshaveidentifiedfivemassextinctionsinEarth’shistory,though
somebelievetherehavebeenmore.Thesefivemassextinctionsarethe:
• Ordovician-Silurianmassextinction,
• LateDevonianmassextinction,
• Permianmassextinction,
• Triassic-Jurassicmassextinction,and
• Cretaceous-Tertiarymassextinction.
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Ordovician-Silurian(End-Ordovician)
Approximately440millionyears,attheendoftheOrdovicianperiodof
Earth’shistory(thesecondperiodofthePaleozoicEra)mostofthe
lifeformsontheplanetlivedinthesea.FarmoreoftheEarth’ssurfacewas
coveredbywaterthanitistoday,withsealevelsasmuchas600meters
higher.
Whenmassiveglaciersformed,aniceagebeganthatwouldlastfor
another20millionyears.Muchoftheplanet’swaterwaslockedupinice,
andtheseasshrankaway.Atleasthalfofallmarineanimalspecieswere
wipedout.
SpanningtheendoftheOrdovicianperiodandthebeginningofthe
Silurianperiod,thiswasthesecondlargestmassextinctiontheEarthhas
seen.
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MASS EXTINCTION
LateDevonian
Somescientistsbelievethatthenextmassextinction,knownastheLate
Devonianextinction,wasactuallyaseriesofextinctionsthattookplace
overperhaps20millionyears.Duringthattime,Earthlostapproximately
70%ofitsmarinespeciesandnearly75% ofitsentirespecies.
TheDevonianperiodissometimescalledthe“AgeofFishes”becauseof
thenumberofnewfishspeciesthatarose.ButtheDevonianperiodalso
sawthedevelopmentofEarth’sfirstforests,whichmayhavecontributed
tothemassextinction.
Plantsconsumecarbondioxide,awarminggreenhousegas,andproduce
oxygen.Scientiststhinkthattherapidlygrowingforestscausedcarbon
dioxidelevelstofall,coolingtheclimatetothepointthatittriggeredthe
LateDevonianmassextinction.
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Permian-Triassic(End-Permian)
DuringthePermianperiod,glaciersmeltedandtheclimatewarmed.
Plantsandinsectsevolvedrapidly,amphibiansthatwouldeventually
evolveintomammalsappeared,andbiodiversityincreaseddramatically.
Butallofthatwasjeopardised bythemassextinctionthatoccurredatthe
endofthePermianperiod,some250millionyearsago.Itwasthelargest
massextinctionintheplanet’shistory.About96% ofallspecies
disappeared,includingmanyvertebrates,whichiswhythePermian-
Triassicmassextinctionissometimescalledthe“GreatDying.”
Nocraterhasbeenfoundtoconfirmthebeliefofmanyscientiststhatthis
massextinctionwastriggeredbytheimpactofanasteroidorcomet.
AnothertheoryisthatvolcanicactivitycausedtheGreatDying.
DuringtheTriassicperiodthatfollowedtheextinction,dinosaursappeared
anddominatedthelandscape.Interestingly,alllivingthingsonEarthtoday
aredescendedfromthe4%ofspeciesleftafterthePermian-Triassicmass
extinction.
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Triassic-Jurassic(End-Triassic)
TheTriassicperiodopenedtheMesozoicEra,knownasthe“Ageof
Reptiles”whenlifeonlandwasbeginningtodiversify.Theclimatewas
generallydry,withseasonalcoastalmonsoons.DuringtheTriassicperiod,
whichlastedforroughly50millionyears,lifeintheseasbegantorecover
fromtheGreatDying.BytheendoftheTriassicperiod,flyingreptiles,
dinosaurs,andearlymammalshadappeared.
TheTriassic-Jurassicmassextinctionwasnotasingleeventbutratherthe
combinedeffectoftwoorthreewavesofextinctionthatoccurredovera
spanof18-20millionyears,endingapproximately200millionyearsago.
Scientiststhinkclimatechange,volcanicactivity,andperhapsanasteroid
impactmayhaveplayedrolesinthismassextinction.
Biodiversityintheseasdecreasedbyapproximately20%.Manyspeciesof
largeamphibiansandearlymammalswerewipedout,butlargenumbers
ofearlydinosaurssurvivedandwouldcontinuetoevolveinanddominate
theJurassicperiod.
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Cretaceous-Paleogene(EndCretaceous)
Nomassextinctionhasbeenstudiedasmuchastheonethatmarkedthe
transitionfromtheCretaceousperiodtothePaleogeneperiodsome65
millionyearsago.Thismassextinctionisofgreatinteresttoscientists
becauseitwipedoutthedinosaursandpreparedthewayfortherapid
diversificationandevolutionofmammals.Itwasn’tonlythedinosaursthat
perished.Nearlyhalfofallplantandanimalspeciesdisappearedduring
theCretaceous-Paleogenemassextinction.
Unlikeearliermassextinctions,thisoneseemstohavebeensudden,at
leastingeologicterms.Thereisstrongevidencethatalargemeteoriteor
smallasteroidhittheEarth,andanimpactcraterapproximately180kmin
diameterhasbeenfoundbeneaththeYucatanPeninsulainMexico.
Thereisalsostrongevidenceofenormousvolcaniceruptionsoveraperiod
ofapproximatelya millionyearsattheendoftheCretaceousperiod.
Manyscientistsbelievethatboththeasteroidimpactandthisvolcanic
activitycontributedtothemassextinctionthatkilledoffthedinosaursand
markedaturningpointinEarth’shistory.
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Timeline
ThisillustrationshowsthefivemajormassextinctionsinEarth’shistory
andonemorethatisthetopicofmuchdebate.
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TheSixthMassExtinction
ManyscientistsbelievethatEarthisnowexperiencinganothermass
extinction.Undernormalcircumstances,asmanyasfivespeciesbecome
extincteveryyear,whichisdescribedasthenatural“background”rateof
extinctions.Currentestimatessuggestthatrightnowwe’relosingdozens
ofspecieseachandeverydayandthatasmanyashalfofallspeciesmay
beextinct,orclosetoit,bythemiddleofthiscentury.
Whatsetsthiscurrentsituationapartfromallpreviousmassextinctionsis
thatwehumansareresponsible.Arecentstudyshowsthatvertebrate
species(mammals,birds,reptiles,amphibiansandfishes)arebecoming
extinctabout114timesfasterthantheywouldhavewithouttheinfluence
ofhumanactivity.Humanactivitiesarecausingthehabitatloss,
introductionofinvasive,non-nativespecies,pollution,oceanacidification,
andclimatechangethataredevastatingmanyspecies.Itmaybepossible
topreventatruesixthmassextinctionthoughwidespreadconservationof
threatenedspecies,preservationofhabitats,andclimatestabilisation.
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AustralianCurriculumMapping
GRADE5SCIENCE(ACSSU043):Livingthingshavestructuralfeaturesand
adaptationsthathelpthemtosurviveintheirenvironment.
GRADE6SCIENCE(ACSSU094):Thegrowthandsurvivaloflivingthingsare
affectedbythephysicalconditionsoftheirenvironment.
YEAR7SCIENCE(ACSSU112):Interactionsbetweenorganisms,including
theeffectsofhumanactivitiescanberepresentedbyfoodchainsandfood
webs.
YEAR9SCIENCE(ACSSU176):Ecosystemsconsistofcommunitiesof
interdependentorganismsandabioticcomponentsof
the environment; matter andenergyflowthroughthesesystems.
YEAR10SCIENCE(ACHGK070):Human-inducedenvironmentalchanges
thatchallengesustainability.
SUSTAINABILITY(01.1):Thebiosphereisadynamicsystemproviding
conditionsthatsustainlifeonEarth.
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