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A DA P T I V E RA D I AT I O N
Howdospeciesrespondtoenvironmentalpressures?
OVERVIEW
Studentsanalyzecharacteristicsofsixpterosaurstodeterminetheroleof
adaptiveradiationintheirevolutionfromacommonancestor.
Forthecompleteactivitywithmediaresources,visit:
http://www.nationalgeographic.org/activity/adaptive-radiation/
Program
DIRECTIO NS
1.Discussconvergentanddivergentevolution.
Reviewthedifferencebetweenconvergenceanddivergence.Ontheboard,
sketchpathscomingtogether(convergence)andonepathsplittingintwo
directions(divergence).Tellstudentsthataspartofevolution,speciescan
convergeanddivergeovertime.Justasspeciesthatarenotcloselyrelated—
suchasbirds,bats,andpterosaurs—canovertimedevelopcharacteristicssuch
aswingstohelpthemsurvive,speciescanalsodiverge.Anewspeciesof
pterosaurcanbreakofffromapopulation,asnewfeaturesevolvethatset
speciesapartfromoneanother.Allowstudentstoaskanyquestions.Then
explainthat,inthisactivity,studentswillexplorewhathappensaspartof
divergentevolution.Thentheywillusepresentationsoftwaretocreatea
summaryslideabouthowdivergentevolutionrelatestopterosaurs.
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2.Analyzepterosaurskullstructure.
Dividestudentsintopairs.Giveeachpairthetwo-pagePterosaurSpecies
handout.Havethemglanceatthepicturesofthepterosaurheadsbriefly.Ask:
Whatdoyounoticeabouttheheads?Acceptavarietyofideasanddescriptions,
andguidestudentstothesimplerealizationthattheseanimalsarebothvery
similarandverydifferent.Askstudentstorelatethecharacteristicsoftheskulls
toeachanimal'slikelyfoodandhabitat.Notethatthebeaksvary;somehave
teeth,arepointed,areduck-like,orarerounded.Guidestudentstorecognize
thatdifferentmouthsenableaccesstodifferentfoods;notethatTapejaracould
likelyscoopfromastreamandPterodaustrowouldhavehadafoodfiltering
ability,whilethetoothedpterosaurswerelikelyabletotearatpreyor
vegetation.Thisvariationinformistheresultofenvironmentalselection,where
animalshaveovertimeadaptedtodifferentenvironmentalconditions,including
foodsources.
3.Determinehowcloselyrelatedthepterosaursare.
Nexthavestudentsdeterminehowcloselythesedifferentanimalsarerelated,
bythinkingaboutwhethertheseanimalsseemtohaveevolvedfromacommon
ancestor,orwhethertheyaremoredistantlyrelated.Havestudentscompare
descriptionsoftheskeletalstructureoftheshoulders,wings,andtailinthe
Anatomycolumn.Ask:Whatcharacteristicsdothepterosaurshaveincommon?
(Thefirstfourhavethesamefixedshoulder,longpalm,andnotail;the
differenceisinthewingspan.Thelasttwohavenotailandashorttail,
respectively.)
4.Analyzeimagesfromthegalleryforcommoncharacteristics.
Showstudentsthesiximagesinthegallery,andhavethemlookcloselyatthe
wings.Ask:Whatcharacteristicdoalloftheseshare?(Studentsshouldrecallthat
allsixhaveanelongatedfourthfinger.)What'sthefunctionofthislongfinger?
(Withthemembraneattached,thepterosaurscouldextendtheirwingstoglide
andfly.)Explainthatthisisakeycharacteristicthatshowsacommonancestry
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amongpterosaurs.
5.Considerthedifferencesamongthegalleryimages.
Havestudentsdiscusswiththeirpartnershowtheymightgroupthese
pterosaurs.Guidestudentstoseethatallbutoneoftheanimalscanbeplaced
inonegroupwithfixedshoulder,longpalm,andeithernotailorashorttail.
Thesefivelivedfrom160millionyearsago(mya)to71mya.Thisgroup,
however,hasatremendousvarietyinskullform,andtheylivedmuchlaterthan
Dimorphodonfrom200mya,withitslooseshoulder,shortpalm,andlongtail.
6.Considerthegeographyofadaptiveradiation.
Explainthatadaptiveradiationisatermthatdescribeswhenmanyorganisms
resultingfromoneearlierancestoraresubjectedtodifferentenvironmental
selectionastheyspreadoverabroadarea.Havestudentslookinthehabitat
columnatthegeographicdistributionofthesepterosaurs.Ask:What
environmentalpressuresmayhaveresultedinthesepterosaursspreadingacross
severalcontinents?PointoutthatbecauseofPangaea,thepositionofthe
continentsvariedoverthetimethatpterosaurslived,soconsiderthatdistances
traveled,thoughfar,werenotasfarasapresent-dayglobewouldrepresent.
7.Summarizeideasabouttherelationshipbetweenthesixpterosaurs.
Havepartnersworktogetheronacomputertodevelopapresentationslide
explainingadaptiveradiationusingpterosaursasanexample.Havestudents
includeatleastthreekeyideasaboutadaptiveradiationandtherelationships
amongthesixpterosaurs.Allowstudentstousetheinformationinthechart,the
imagegallery,andnotesfromthediscussionasreference.
InformalAssessment
Assessstudents'completedpresentationslidesbasedonwhatpointstheychose
toincludeontheslideandhowtheydescribesimilaritiesanddifferences
betweenthesixpterosaurs.Studentscanrefertothesimilaritiesofthesix
pterosaurs'bodystructurestoillustratetheircloseevolutionaryrelationshipand
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thedifferencesintheirskullstructuretoillustratetheirdivergentevolutionand
adaptiveradiation.
ExtendingtheLearning
Havestudentsrevisittheimagesofthesixpterosaursbeforewatchingthefilm
FlyingMonsters3D.Askthemtoconsidertheirownquestionsthatmaybe
answeredinthefilm,suchas"WhydoesTapejarahavesuchalargehead
crest?"Asstudentswatchthefilm,havethemnotedifferenthypothesesforwhy
pterosaursmayhavedevelopeddifferently.
O BJECTIVES
Subjects&Disciplines
Science
Biologicalandlifesciences
Ecology
Paleontology
LearningObjectives
Studentswill:
analyzecharacteristicsofspeciestodeterminehowcloselyrelatedtheyare
explainthemeaningof
TeachingApproach
Learning-for-use
TeachingMethods
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Discussions
Informationorganization
Visualinstruction
SkillsSummary
Thisactivitytargetsthefollowingskills:
CriticalThinkingSkills
Analyzing
Applying
Understanding
NationalStandards,Principles,and
Practices
N AT I O N A L S C I E N C E E DU C AT I O N S TA N DA RDS
•(9-12)StandardA-2:
Understandingsaboutscientificinquiry
•(9-12)StandardC-3:
Biologicalevolution
PREPARATIO N
WhatYou’llNeed
M AT E RI A LS YO U P RO V I DE
Paper
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Pens
RE Q U I RE D T E C H N O LO G Y
InternetAccess:Optional
TechSetup:1computerpersmallgroup,Presentationsoftware,Projector
Plug-Ins:Flash
P H Y S I C A L S PA C E
Classroom
G RO U P I N G
Large-groupinstruction
Small-groupinstruction
RE S O U RC E S P RO V I DE D: H A N DO U T S & W O RK S H E E T S
PterosaurSpecies
RE S O U RC E S P RO V I DE D: I M A G E S
PterosaursGallery
BACKGRO U ND & VO CABU L ARY
BackgroundInformation
Theearlierpterosaurshadlongtailsandflightmembranes,calleduropatagia,
connectingthetailswiththehindlegs.Thisarrangementgavethepterosaurs
stabilityinflight,butitalsomeantthattheycouldn’twalkverywell.Accordingto
thefossilrecord,theseearlypterosaursvariedrelativelylittleintheirdesigns:
size,teeth,andheadcrests.ThissituationchangedoncethePterodactyloids
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evolvedinthemiddleJurassicPeriod.Theseanimalshadnotailsandthusno
membraneconnectingtothehindlegs.Theycouldthereforewalkmuchbetter.
Inaddition,theirwingstructure,thoughitmadeflightmoreunstable,alsomade
itmoremaneuverable.Consequently,thePterodactyloidswereabletobemore
flexibleintheirlifestylechoices,andtheyevolvedtofillmanymorenichesthan
theirforebearerscould.Pterosaurdesignstookoffinmanydirections,leading
toastunningvarietyofanimals.
PriorKnowledge
["evolution","classification","convergentevolution"]
RecommendedPriorActivities
ExploringVertebrateClassification
Vocabulary
Term
Partof
classificationnoun
evolution
Definition
Speech
noun
groupingbasedonphysicalandgenetic
characteristics.
changeinheritabletraitsofapopulationovertime.
ForFurtherExploration
Websites
NationalGeographicEntertainment:FlyingMonsters3D
©1996–2017NationalGeographicSociety.Allrightsreserved.
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