KIDS CORNER MASS EXTINCTION - mygreenworld.org€¦ · MASS EXTINCTION Late Devonian Some scientists believe that the next mass extinction, known as the Late Devonian extinction,

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

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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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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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