ZoologyExercise#21–Chordates–Birds(Pigeon)LabGuideAdaptationsinstructureandfunctionforflightThefeatheristheuniquehallmarkofbirds.Theforelimbsaremodifiedaswings.Hindlimbsareadaptedforwalking,swimmingorperching.Allbirdshavehorny,keratinizedbeakmoldedaroundabonyjawandlayeggs.Thereare4majortypesoffeather:
1. Contourfeathers:provideflightandformforthebird.(ex.Flightfeathers)2. Downfeathers:foundundercontourfeathersandinsulatethebird.3. Filoplumefeathers:hair-likefeatherswhicharedegeneratefeatherswithaweakshaftandtuftofshortbarbs.4. Powder-downfeathers:foundinheronsandegretsanddisintegratetoreleasetalc-likepowdertowaterproofthe
feathers.Abouthalfofallbirdspeciesmigrate.Usuallymovingbetweensouthernwinteringgroundsandnorthern,summerbreedinggrounds.Thismigrationallowsbirdstoexploitseasonalchangesinabundanceofinsectsandavoidbirdpredators.Migrationexpandslivingspaceandreducesaggressiveterritorialbehavior.Italsoallowsbirdstoavoidclimaticextremesandfoodshortages.Toflythefollowingadaptationsmustbemet:
1. Wings:support/propulsion2. Respiratorysystem:mustmeethighoxygendemandsandcoolthebody3. Bones:mustbelightbutrigid
a. Theyarelacedwithaircavities(pneumatizedbones),butverystrongb. Thebirdskullislighterandfusedintoonepiecewiththebraincaseandorbitsverylargetoholdalarger
brainandeyec. Legbonestendtobeheavierwhencomparedtomammalstolowerthecenterofgravityd. Thevertebralcolumnisveryrigidandfusedexceptforcervicalvertebraee. Ribsaremostlyfusedwiththevertebrae,pectoralgirdle,andsternumf. Thesternumhasalarge“keel”toanchorflightmusclesg. Mostcaudalvertebraearefusedintoa“pygostyle”
4. Digestion/circulation:meethigh-energydemandsforflight5. Nervoussystem:havesuperbsensorysystemsforhighvelocityflight
Birdbeakswilloftenrevealtheirfoodhabits(seedeater,insecteaters,etc.).Duetoaveryhighmetabolicrate,birdsneedquiteabitoffoodwhencomparedtotheirbodyweight.Hummingbirdscaneat100%oftheirbodyweighteachday,whilechickenseatabout3.4%eachday.Birddigestivesystemshaveveryefficientdigestionwhichcandigestfoodrapidly.Ashrikecandigestamousein3hoursandaberrycanpassthroughthedigestivetractofathrushinjust30minutes.
INTEGUMENTARY/BODY-Modificationforflight:FEATHERSprovidelift;arestreamlinedfordecreasedairresistance;insulateagainstheatlossSKINisverythinsoitweighsless
BirdsaretheonlyanimalswithFEATHERS.FeathersaremodifiedscalesmadeofKERATIN.TheirfunctionistoPROVIDELIFTinflyingandPRESERVEBODYHEAT.Feathersalsoprovidecolorationtoattractamateandhidefrompredators.Examineafeathercarefully:Thestructureofafeathercombinesmaximumstrengthwithminimumweight.HollowquillsgrowfromtinypitsintheskincalledFOLLICLES.TwoVANESdeveloponoppositesidesofacentershaftcalledtheRACHIS.Each(rachis)vanehasmanybranchescalledBARBS.Thebarbsarezippedtogether“likeVelcro”bymicroscopichookscalledBARBULES.
BirdsstraightenandcarefortheirfeathersbyrubbingthemwithoilsecretedbyaPREENGLANDatthebaseoftheirtail.Thiszippingtogetherofthebarbulesiscalled“preening”.BirdsperiodicallyMOLTorshedtheirfeathersandgrownewones.Thishelpstoavoidbarespots.Flightandtailfeathersarelostinpairs(oneoneachside)tomaintainbalance.Somebirdswillmoltcontinuouslysoflightisnotimpaired.Somewaterbirdsmaybegroundedforashorttimesincetheirfeathersmaybemoltedallatonce.Birdslivingintemperateclimatesusuallyreplacetheirflightfeathers(calledaMAJORMOLT)duringlatesummerafternestingseason.Mostonlymoltonce.
ThefleshybitofskinthatliesoverthebeakiscalledtheCERE.FindtheNICTITATINGMEMBRANE,theEAROPENING,BEAK,andEXTERNALNARES.
Birdsseeincolorandhavekeenvisionwhichisimportantintakingoff,landing,spottinglandmarks,hunting,andfeeding.MosthaveeyesonthesidesoftheirheadwhichgivesabirdawiderangeofvisionThisarrangementismostoftenseeninbirdswhichmaybepreyofotheranimalssotheycanwatchforpredatorsmoreeasily.
BirdswithbotheyesonthefrontoftheirheadhavebetterBINOCULARvision(DEPTHPERCEPTION)anecessityforhunting.Thisarrangementismostoftenseeninbirdsthatarepredatorssuchasowls,hawks,andfalcons.
Hearingisimportanttosongbirdsandinnocturnalbirdsthatmusthuntforpreyinthedark.BirdslackobviousexternalearsandhavetheirTYMPANICMEMBRANEinside.Birdsdonothearatveryhighfrequencies,butareveryadeptatdistinguishingdifferenceinpitchandintensities.Senseofsmellispoorexceptinflightlessbirds,ducksandvultures
NERVOUSModificationforflight:LargeBRAINforbodysize=“intelligence”BiggerCEREBRUMallowsmorecomplexbehavior(problemsolving;learning;navigation;nesting;nestbuilding;caringforyoung)BiggerCEREBELLUMforequilibrium/musclecoordinationduringflightBiggerOPTICLOBESforbettervision;colorvision;eyesarelargeandalmostimmobile(birdsofpreyhaveeyesdirectedforwardtoprovidedepthperception
ConcentrationofIRONinthebrainofmigratingbirdsisthoughttobeusedtodetectmagneticfields(actslikeacompass)SKELETALModificationforflight:Bones=thin&HOLLOW;ManybonesareFUSEDforstrength;AIRSACSfromlungsextendintosomebonesmakingthemlessdensePYGOSTYLE(fusedlowervertebrae)supporttailforlift&brakingduringflight; FURCULA(fusedcollarbones)stabilizeshouldersduringflight; STERNUM(largebreastbone)toattachflightmuscles
Birdbonesarehollowtomakethemlessdensethanbonesofnon-flyinganimals.Somebones(FURCULA,PYGOSYTLE)arefusedtomakethemstronger. MUSCULARModificationforflight:BEGIN,byremovingfeathersfromtheventralsideofthepigeon.Now,withyourscalpel,makeamidventralincisionfromtheuppernecktothecloaca.UsingtheBLUNTendofaprobe,separatetheskinandfeathersfromtheunderlyingmusculatureoftheneck,breast,andabdomen.BECAREFULintheneckregionnottodamagethecrop.Thiscropliesjustbeneaththeskinatthebaseoftheneck.Cutawaytheloosenedskin
fromthebreastmusculaturedowntothewinginsertionandfromtheabdomen.Itisnotnecessarytoremovetheskinandfeathersfromthehead,back,wings,legs,andtail.Continuetodissectawaythebreastmusclesfromthekeel,baseofthesternum,andcoracoid.Usecaretopreventdamagetotheunderlyingorgans.Cutthroughtheribs,anteriorendofthesternum,andcoracoidonbothsidesandremovetoexposetheviscera.Removeanyremainingskinfromtheventralsideoftheabdomenasfarposteriorlyasthecloaca.LargePECTORALISMAJORmusclesattachtosternum(keel)anddepressthewingsduringflight.Abird’spectoralmusclecanmakeupoverathirdofitsbodymass.TheSUPRACORACOIDEUSmusclesisalsoattachedtothesternum(keel)andwillraisethewing.Itwillpullthewingupfrombelowbywayofa“ropeandpulley”typeofarrangement.Toe-lockingmechanismsareusedtopreventaperchingbirdfromfallingwhileasleep.
DIGESTIVEToexaminetheoralcavity,cutthroughtheangleofthejawswithscissors.Befamiliarwithalllabeledparts.SKETCH(ORALCAVITY)Modificationforflight: 2partstomachtospeedfoodthroughsystem;Cropforstorageallowsbirdstoeatwhenstomachisfullsofoodisalwaysmovingthroughdigestivesystem;Foodfuelshighmetabolism(ENDOTHERMIC)forenergyforextendedactivitysuchasflyingExcessfoodstoredasFATforenergyduringlongflights(migration)LongSMALLINTESTINEtoabsorblotsofnutrientsShortLARGEINTESTINEtogetridofdigestivewastefaster SKETCH(DIGESTIVESYSTEM)
Thelargeamountofenergyneededtoflyandregulatebodyheat(ENDOTHERMIC)isobtainedbyaquickandefficientdigestivesystem.BirdshaveNOTEETHtochewtheirfoodbeforeitpassesdownthelong,muscular,ESOPHAGUSintotheCROPwhichstoresfoodwaitingtobedigested.BirdshaveaTWOPARTSTOMACHtospeeddigestion.Inthefirstchamber,thePROVENTRICULUS,secretesacidanddigestiveenzymesbeginbreakingdownthefood.ThesecondmuscularportioncalledtheGIZZARDcontainssmallrocksthebirdhasswallowedwhichhelpinGRINDINGthefood.FoodisthenpassedintotheverylongSMALLINTESTINEwheredigestioniscompletedandnutrientsareabsorbed.TheshortLARGEINTESTINEabsorbswaterfromandconcentratesdigestivewaste.TheCOLICCAECAarefoundatthejunctionofthesmallandlargeintestine.Thesesmallpouchescontainbacteriathataidindigestingplants.DigestivewasteismixedwithurinecontainingURICACIDintheCLOACAbeforeexitingthroughtheVENT.TheLIVERandPANCREASstillprovidedigestiveenzymes.Birdsofprey,suchasowls,willformapelletofindigestiblematerialintheproventriculusandejectit.
ENDOCRINEModificationforflight:THYROIDmaintainsHIGHMETABOLISM(burnsglucose)toprovideenergyforflightPANCREAS(makesINSULIN&GLUCAGON)regulatesbloodsugarlevelssofuelisavailabletopowerflightmusclesENDOTHERMICmetabolismprovidesenergyforextendedactivity(flight)CIRCULATORYModificationforflight:
1. Heartlargeforsizeofbody2. 4chamberheart(SEPTUMtotallyseparatesventricleinto2)=most
efficient/faster,2loopsystemwhichisfaster/givesextrapushtobloodgoingtobody
3. Rapidheartratemovesoxygen/nutrientstobodyfasterBirdshaveaCLOSEDCIRCULATORYSYSTEMwith2LOOPS(PulmonaryandSystemic)justlikeamphibians&reptiles.ThedifferenceinbirdsistheCOMPLETESEPARATIONoftheventriclebyaSEPTUMintoa4CHAMBERHEART(2atriaand2ventricles).Thesinusvenosusandconusarteriosushavedisappeared.Thebrachialandpectoralarteriestowingsandbreastareunusuallylarge.ThelargestveinreturningtotheheartistheVENACAVA.ThelargestarteriescarryingbloodawayfromtheheartarethePULMONARY(tolungs)andtheAORTA(tobody).Comparedtoreptilesandmostothervertebrates,birdshaveaRAPIDHEARTBEAT.LikeamphibiansandreptilestheSPLEENstillmakes,stores,andrecyclesredbloodcells.Likereptilesandamphibians,birdredbloodcellsHAVENUCLEI.HumanRBC’sdon’t.
RESPIRATORYModificationforflight:
1. SuperEfficientrespiratorysystemtomeetHIGHOXYGENDEMAND2. AIRSACSallowoxygenatedairinlungsduringbothINHALEandEXHALEtoprovidemoreoxygenduringhighactivity
(flight)3. AIRSACSfromlungsextendintothethorax,abdomenandbonestodecreasedensity4. ALVEOLIinlungsincreasesurfaceareaformoregasexchange.
BirdshavetheMOSTEFFICIENTrespiratorysystemofanyterrestrialvertebrate.Rapidmetabolismrequiresanabundantsupplyofoxygen.Yetsomebirdsmigratethousandsofmilesathighaltitudes(upto23,000ft)whereoxygenlevelsareverylow.AirentersthroughEXTERNALNARESatthebaseofthebeakandmovesintotheTRACHEAthroughtheGLOTTISopeninginthebackofthemouthcavity.TheairmovesdowntheTRACHEAandbranchesintotwoBRONCHI(sing.
BRONCHUS).Fromtheresomeoftheairentersthelungs.However,about75%oftheairbypassesthelungsandflowsdirectlyintothePOSTERIORAIRSACSthatextendfromthelungsandoccupyalargeportionofthebird’schestandabdominalcavity.Thesesacsalsoextendintosomeofthelongbones,alsoREDUCETHEDENSITYofthebird.GASEXCHANGEDOESNOTOCCURINTHEAIRSACS.TheirfunctionistoSTOREAIR.WhenthebirdexhalestheLOWOXYGENAIRfromitslungsmovesintotheANTERIORAIRSACSandtheHIGHOXYGENAIRfromtheposteriorairsacsmovesintothelungs.Thisway,thebirdhashighoxygenairinitslungsatalltimes...bothontheinhaleandontheexhaleALVEOLIinthelungsincreasesurfaceareaforgreatergasexchange.Itwilltake2respiratorycyclesforasinglebreathofairtopassthroughthesystem.TheSYRINX(voicebox),whichproducessound,isadiamondshapedorganlocatedwherethetracheasplitsintothe2bronchi.Byregulatingtheflowofairbirdscanproducesongsofgreatrangeandcomplexity.Malebirdssingtowarnawayothermalesandtoattractfemales.
SKETCH(CIRCULATORY/RESPIRATORYSYSTEM)EXCRETORYModificationforflight:NoUrinarybladder=lessweightNitrogenwasteeliminatedasURICACID(needstheleastwatertodilute); Wasteeliminatedasmade/NourinestorageTheavianexcretorysystemislightweightandefficient.TheexcretoryorgansinbirdsisrepresentedbytheMETANEPHRICKIDNEYS.Theseelongatedbrownishorgansarelocatedalongthebackbodywallunderthereproductiveorgansoneithersideofthespinalcord.ThekidneysREGULATEION/WATERBALANCEofbloodandtissuesandREMOVENITROGENWASTE.Unlikeothervertebrates,birdsDONOTSTOREURINE…thereisNOURINARYBLADDER!ThekidneysfilternitrogenwastefromthebloodintheformofURICACID.Thisformistheleasttoxicandrequirestheleastamountofwatertodilute.ConcentrateduricacidwastemovesthroughductscalledURETERStotheCLOACA,whereanyremainingwaterisre-absorbed.ItmixeswithdigestivewasteandiseliminatedthroughtheVENT.Birddroppingsareamixtureoffecesanduricacid(thewhitecoloredmaterialyouseein“birdpoop”).Somemarinebirdswillalsoexcretelargeamountsofsaltviaglandsaboveeacheye.Thisisduetotheirdietanduptakeofseawater.Saltsolutionwillalsorunoutofthenostrils. REPRODUCTIVEModificationforflight:FemaleshaveanOVARYandOVIDUCTononly1side.Normallyontheleft.(lessweight)Therightovaryandoviductdegenerate.Ovaryenlargesduringbreedingseason;shrinksinsizerestofyearOVIPARITY=Layeggsoutside(lessweightifeggNOTkeptinbody)InmalesspermisproducedintheTESTESnearthekidneys.Testesremainverysmalluntilthebreedingseason.Thentheycanenlargeupto300times.SpermpassesthroughasmalltubecalledVASDEFERENS(plural:VASADEFERENTIA)intotheCLOACA.But,maybestoredinagreatlyenlargedSEMINALVESICLE.
Maleslackapenis,soduringmatingthemalepresseshiscloacaagainstthefemale’scloacaandreleasessperm.Rememberseeingalltheeggsinfish,frogs,andturtles…eggsareheavy!Havingasingleovarylightenstheloadforflying!Birdslayamnioticeggs.TheOVARYproducestheeggs,theinfundibulum(firstpartoftheoviduct)receivestheeggsandspecialglandsaddthealbumenasittravelsdowntheOVIDUCT.Theshell/shellpigmentsareaddedfartherdowntheoviduct,justlikeinaturtle.Fertilizationwilltakeplaceintheupperoviduct.EggspassthroughtheCLOACAandVENTtotheoutside.CALCIUMCARBONATEmakestheshellhardsobirdscansitontheeggstokeepthemwarm.Spermcanremainaliveforseveraldaysafterasinglemating.SKETCH(EXCRETORY/REPRODUCTIVESYSTEM)
Over90%ofbirdspeciesaremonogamous(onlymatewithonepartnerduringeachbreedingseason).Some(swans/geese)mateforlife.Inmonogamousrelationships,bothpartnerssharetheparentalcareequally.Malebirdswillestablishterritoriesandsingtoannouncehispresencetofemalesanddriveawayothermales.Femaleswillwanderabouttoselectthemalewhichoffersthebestchanceatreproductivesuccess.Mostbirdslayeggsinnests.Nestsholdeggs,concealyoungbirdsfrompredators,provideshelterfromtheweather,andsometimesattractamate.Oneorbothparentsincubate,(WARM)theeggsbysittingonthem.Athickened,featherlesspatchofskinontheabdomencalledaBROODPATCH,allowsskintoeggcontactformorewarmth.Mostsongbirdeggswillhatchafter14days.
InbirdsintheorderColumbiformes(pigeons&doves)thecropinbothmalesandfemalessecretesanutritiousmilk-likefluidcalledCROPMILKtofeedtheyoung.BirdsthatlayeggsinnestsonornearthegroundwheretheyaremorevulnerabletopredatorshavePRECOCIALYOUNG(babiesthatcanwalk,swim,andfeedthemselvesshortlyafterbirth).Thisallowsthebabybirdstobemobilesoonerandincreaseschancesforsurvivalbybetterescapingpredators.Birdsthatlayeggsinnestshigherupintreesorplaceswherepredatorscan’treachaseasilyhaveALTRICIALYOUNG(babiesthatarefeatherless,blind,andhelplesswhichmustbefedandcaredforbytheparents).Thiskindofbabywouldquicklybeeatenifitwaslaidinanestontheground!Hatchingthiskindofbabiesuphighprotectsthemuntiltheyaremoremature.
Analysis1.Whatdoyoubelievehasshapedtheformandfunctionofbirds?2.Birdshavemanydifferentkindsoffeathers.Dosomeresearchandlistatleast5differentkindsoffeathersandexplaintheirfunctioninthatbird.3.Theskeletalstructureofbirdsisverydifferentwhencomparedtomanyothergroupsofanimals.Whatadaptationshavehadtooccurinorderforthisgroupofanimalstobesuccessful?4.Theseskeletalpartsareextremelyimportanttothebirdinregardstoflight.Explaintheirimportance. a.Pygostyle: b.Furcula: c.Sternum:5.Therearemanymusclesattachedtotheskeletalsystemthatassistinflight.Describethemusclesinvolvedandhowthismechanismofflightisaccomplished.(Besuretodiscusstheupwardanddownwardstrokesasflightoccurs)6.Thetongueofabirdispoorlysuppliedwithtastebuds.Ifthat’sso,whatisitbeingusedfor?7.Birdsareconsidered“negativepressurebreathers”likemammals,buttheylackadiaphragm.Explainhowairiscirculatedthroughouttheanimal.
8.Abouthalfofallbirds“migrate”.Explainwhatmigrationisandthenexplainhowscientistsbelievemigrationoccursphysiologicallywiththebird.9.Birdspractice“oviparity”.Explainhowthisprocessoccursinbirds.10.Birdsareknownfortheirfastreactions,balance,coordinationandinstinctivebehavior.Birdbrainsarerelativelylargerthanthoseofreptilesbutsmallerthanthoseofmammals.Whatdoyouthinkthisindicatesabouttheirabilitytoreasonandlearn.(Becompleteinyouranswerbyusingexamplesfromyourresearch)11.Birdsareoftendescribedas‘glorifiedreptiles”.Whywouldsomeonemakethisstatement?Makecomparisonsbetweenthosecharacteristicsseenandreptilesandthoseseeninbirds.Whathavestayedthesameandwhathaschanged?Pleasemakesureyouhavedonesomeresearchpriortoansweringthisquestions.Beabletosupportyourstatements.
