Lab 1 - External Characteristics - POELABGeneral Vertebrate Diversity Lab 1 Lab 1 External...

GeneralVertebrateDiversityLab

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Lab 1

External Characterist ics of Vertebrates

Objectives 1. Listthemajorgroupsofvertebrates.2. Describethedefiningcharacteristicsofvertebrates.3. Useexternalcharacteristicstodistinguishbetweenthemajorvertebrategroups.

Introduction VertebratesareauniquelineageoforganismsthatdescendedfromacommonancestordatingbacktheCambrianover500millionyearsago.Today,allvertebratespossesscertaincharacteristicsinheritedfromthatcommonancestor.Overtime,vertebrateshaveevolvedintomultiplelineages,eachwithuniquederivedcharacters.Asyouworkthroughthislab,observethesimilaritiesanddifferencesbetweenthesevertebrategroups.

Jawless Fish - Agnatha

I. Myxinoidea – Hagfish Hagfisharejawlessscavengersthatfeedupondyinganddeadfishesandwhales.There

are75knownspeciesofhagfish,allfoundinmarineenvironments.Examinethespecimenofthehagfishandbeabletolocateandknowthefunctionofthelabeledstructures.

1. Slimeglands,whichoccuroneachside,onepersegment.Slimeglandsareoftenmostevidentintheposteriorregion(butcanbehardtosee).

2. Externalgillopenings.Gillslitsvaryinnumberfrom1-15pairs.3. Oraltentaclesorbarbels.Whatmightbethefunctionoftheseoraltentacles?


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II. Petromyzontoidea - Lamprey Theapproximately40speciesofjawlesslampreysrangeinsizefrom25cmtoabout1

meter.Manyspeciesareborninfreshwater,spending5ormoreyearsinalarvalformbeforetheymetamorphoseintoadultformandmigratetomarinehabitats.Somespeciesarefoundexclusivelyinfreshwater.Manyspecies,includingthespecimensinlab,areparasitic.Theycanbeseenattachedtotheoutsideoftheirhosts,whichareoftenotherfishes.

Thebodycanbedividedintothreeregions:

1) Head(extendingthroughthegillarea)2) Trunk(gillsto)cloaca),3) Tail(posteriortocloaca).

Observethetwodorsalfinsandcaudalfin.Atthefrontofthehead,observethebuccaltunnelthatisfringedwithpapillaeandlinedwithhornyteeth.Asingle,mediannostrilislocatedfarbackonthetopofthehead.Justbehindthenostrilisthepinealeyeorcornea.Itisanovalareathatisoftenslightlydepressedandgenerallyalightercolorthantherestoftheskin.Onthesidesoftheheadisapairoflidlesseyes.Behindtheeyesarelocatedsevenpairsofexternalgillslits.


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Gnathostome – Jawed Fishes

III. Chondrichthyes-Cartilaginous fish/Sharks Sharksandrays(Elasmobranchii)andratfishes(Holocephali)aremembersofthetaxon

Chondrichthyes,whichincludesover900species.Allbut28speciesarefoundinmarinehabitatsandmostarepredatorycarnivores(thoughseveralfeedonplankton).Examinethedogfishsharkspecimensandthemicroscopeslidestoidentifyandlearnthegeneralfunctionofthelabeledstructures.Thebodyisdividedintothehead,trunk,andcaudalregions.

Ontheheadlocate:

1) Themouth,2) Theeyes,3) Thespiracles,4) Thenostrils(eachofwhichis

partiallysub-dividedbyaflapofskinthatSeparatesthestreamofwaterflowingintoandoutofthenostril)

5) TheampullaeofLorenzini6) Externalgillslits,Formingthe

divisionbetweentheheadandtrunkarethe.Howmanypairsofgillslitsdoesthedogfishsharkpossess?

Onthetrunkofthesharklocate

7) Thepairedpectoralfins8) Pelvicfins.Thepelvicfinswillvarybetweenthemalesandfemales.Maleswill

havestiff,groovedcopulatoryorganscalledclaspersonthemedialsidesofthepelvicfins.AllChondrichthyeshaveinternalfertilizationanddevelopment.

9) Anteriordorsalfin.Thedorsalfinhasalargespineinfrontofit,whichisdefensive.

10) Thelaterallineisfoundalongthesidesofthebodylookforafine,light-coloredstripethatis.

11) Placoidscales.Notetheroughnessoftheskinwhenyourunyourfingersfromtheposteriortotheanteriorend.Howdoesthestructureofthescalesofsharkresembleatooth?

Onthetailendofthesharklocate

12) Thecloacaformsthedivisionbetweenthetrunkandtailoftheshark.

13) Onthedorsalsideofthetailistheposteriordorsalfinwithaspine.

14) Thetailendsinthelargeheterocercalcaudalfin.Notehowthebodyaxisturnsupintothedorsallobeofthecaudalfin.


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1. Anteriordorsalfin2. DorsallobeofCaudalfin3. Endolymphaticpores4. Excurrentapertureofnaris5. Externalgillslits6. Externalnaris7. Externalspiracularpore8. Eye9. lncurrentapertureofnaris10. Lateralline11. Lowereyelid

12. MucousporesofAmpullaeofLorenzini

13. Nasalflap14. Pectoralfin15. Pelvicfin16. Placoidscales17. Posteriordorsalfin18. Eye19. Snout20. Spineofdorsalfin21. SpiracularvalvewithPseudo-branch onposteriorwall22. Uppereyelid23. VentrallobeofCaudalfin


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IV. Osteichthyes - Bony fish Osteichthyesisthemostdiversegroupofvertebrates(ca.26,000-30,000species)andincludestwomajorgroups:Actinopterygii,theray-finnedfishes,andSarcopterygii,thelungfishesandthecoelacanth.InlabwewillfocusontheActinopterygii.Actinopterygianfisheshavefinsthataresupportedentirelybydermalfinrays.ThedifferentgroupsofActinopterygianfishesaredifferentiatedbyanumberofexternalcharactersincludingtypeofcaudalfin(heterocercalorhomo-cercal)andtypeofscale(ganoid,ctenoid,cycloid).Ingeneral,themoreprimitiveActinopterygiipossessaheterocercaltailandganoidscalesandthemorederivedlineagespossesshomocercaltailsandcycloidorctenoidscales.Examinethespecimensandmicroscopeslidestolocateanddescribethegeneralfunctionofthelabeledstructures.

Onthegarspecimen,whichrepresentsamoreprimitivegroupofActinopterygii,observethe

1) Heterocercalcaudalfinandthepositionofthemouth.2) Theganoidscalesunderthemicroscope.Ganoidscalesarecomposedofenamel

(ganoin)ontheuppersurfaceandboneonthelower.

ThemostdiversegroupofActinopterygiiistheTeleosti,whichincludesmostofthefamiliarfish(e.g.,eel,perch,herring,pike,salmon,trout,guppy,flounder,tuna,sunfish,etc.).Observetheperchspecimens.Thebodyisdividedintothehead,trunk,andtail.

Nostril

Spinydorsalfin

Operculum

SoftDorsalFin


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Onthehead,locatethepositionof

3) Themouth.4) Thenostrils5) Eyes(notehowtheyprotrudefromthesidesofthefish).6) Theoperculum.

Onthetrunkofthefishlocate

7) thepairedpectoralfins8) Pelvicfins.9) Theanteriorandposteriordorsalfins.10) Thelateralline.11) Thetrunkendsatthecloaca.12) Thecaudalfinthatislocatedattheendofthehomocercaltail.Thevertebralcolumn

doesnotextendintotailcaudalfin.13) Themoreadvancedbonyfisheshaveeithercycloidorctenoidscales.Thesearethinand

flexibleandarearrangedinoverlappingrows.Examinetheexamplesofcycloidandctenoidscalesunderthemicroscope.


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Cycloidscalesaretypicallycircularinnature.Thescalesgrowinconcentriclayersandhaveasmoothoutermargin.Theyarefoundinthemorederivedray-finfish,theteleost.

Ctenoidscalesresemblecycloidscales,excepttheyhavesmallteethontheirouteredges.Similartocycloidscales,theyalsogrowinconcentriclayersandarefoundinteleost

Cycloidscalesarefoundoftenfoundinfishwithsoftrays,includingthisRiverCarpsucker(Carpoidescarpio).Ctenoidscalesareoftenfoundinfishwithspinyfinrayslikethisgreensunfish(Lepomiscyanelis)


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GanoidScalesaretypicallythickandnotoverlappingandconnectedbypeg-and-socketjoints.Theyarefoundinnon-teleostray-finnedfish(gars,bichirs,bowfins,andsturgeons,andpaddlefish).Ingars,thescalesaregreatlyenlargedtoformarmorplates.

PlacoidscalesarefoundintheChondrichthyesorcartilaginousfishincludingthesharks,skates,andrays.Placoidscalesarebasicallyminiatureteeth,possessingpulpsuppliedbybloodvessels,surroundedbyalayerofdentine.Asthefishgrowsinsize,morescalesareadded.


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Tetrapods

V. Amphibia-Amphibians Amphibiansareanancientlineagedatingbackto370millionyearsago.AllmodernamphibiansareclassifiedastheLissamphibia,whichincludesabout7,000extantspeciescomprising3maingroups:Gymnophiona(caecilians),Anura(frogs),andUrodela(salamanders).Sharedexternalcharacteristicsforthesegroupsinclude1)skinthatisspecializedforgasexchangeandpossesspoisonglands,and2)forelimbswith4digits(frogsandsalamanders).Inlab,wehavespecimensoffrogs,salamanders,andcaecilians.

Gasexchangethroughtheskinisveryimportantforamphibiansallowingthemtoremainsubmergedforextendedperiodsoftime.Itsfunctionisdependentupontheproximityofbloodcapillariestothesurfaceandamoistskinsurface.Moistskinismaintainedbythepresenceofmanymucousglandsintheskin.Poisonglandsintheskinproducenoxiousortoxicsubstancesusedindefenseagainstpredation.

Theeggsofamphibianslackshellsandmustdevelopinamoistenvironment.Many(butnotall)amphibiansgothroughalarvalstage.Someamphibiansretainlarvalfeaturesintosexualmaturity;thisiscalledneoteny.Observethegillsofthemudpuppy

Amphibiansarethemostprimitiveofthelivingtetrapods.Observe4)forelimbswith4digits(fingers)oneachand5)thehindlimbs.Observethedifferencesinlimbstructurebetweenthesalaman-dersandfrogs.Howhavethelimbsofthelatterbeenmodified?Observe6)thetailofthemudpuppy(Necturus).Anuranslackatail.Alltetrapods(aswellasthelungfish)possesschoanaeorinternalnares.Usingtheprobepro-vided,gentlyexaminethe7)nostrilsofthefrog.


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Observetheeyesofthefrogandlocatetheclear8)nictitatingmembrane.Behindtheeye,locatetheround9)tympanicmembrane.Doesthemudpuppyhaveanictitatingmembraneortympanicmembrane?

Amniotes

VI. Testudinata-Turtles Testudinataincludesabout327speciesofextantturtlesthatarefoundinterrestrial,freshwater,andmarinehabitats.Therearetwogroupsofturtles:Cryptodiraincludesabout200speciesandPleurodiraabout50species.Thegroupsaredistinguishedbythewaytheyretracttheirheadsintotheirshells.CryptodiresretracttheirheadsintotheirshellsbybendingtheirnecksinaverticalS-shape;pleurodiresretracttheirheadsbybendingthenecklaterally.CryptodiresaretheonlyturtlesinNorthAmerica.Turtlesareuniqueinthatthepelvicandpectoralgirdlesarelocatedbehindtheribcage.


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Examinethespecimenoftheturtle.Theshelloftheturtleisdividedintothedorsal1)carapaceandtheventral2)plastronThecarapaceandplastronareconnectedby3)thebridge.

VII. Lepidosauria-Squamata-Lizards/Snakes Squamataincludestheapproximately9,000speciesoflizardsandsnakes.Onesharedcharacteroflizardsandsnakesisthepresenceofhemipenes(dualcopulatoryorgans)inmales.Althoughsnakeslackexternalpairedappendagestheyareconsideredtetrapodsbecausetheirancestorspossessedlimbsandbecausetheskeletonsofsomesnakesstillhavevestigial(veryreduced)girdles.Limbreductionhasevolvedrepeatedlyamonglizards,perhapsasmanyas62times.Asyouexaminethespecimensofthelizardsandsnakesobserveboththesimilaritiesanddifferences.

Allsquamatespossess1)epidermalscales.Examinethedifferentlizardandsnakespecimenstoseehowtheshapesandsizesoftheepidermalscalescanvary.Examinethe2)eyesofthelizardsandsnakes.Mostlizardshavemoveableeyelidswhereastheeyesofsnakesarecoveredwithatransparentcap.Lookbehindtheeyesofboththesnakeandthelizard,onwhichonedoyousee3)anexternalearslit?


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VIII. Crocodilia-Alligators/Crocodiles Thereare23speciesofcrocodiliansinthreegroups(Alligatoridae,Crocodylidae,Gavialidae).Thesegroupsaredistinguishedbythesnoutshape.

Examinethealligatorskullandobservetheelongatesnoutwith1)nostrilsonthedorsaltipofsnout.Thenostrilsonthedorsaltipofthesnoutcombinedwithacompletesecondarypalate(likemammalshave)allowcrocodilianstobreathewhenthemouthisunderwater(orfulloffood).Lookattheskulltoseethe2)secondarypalate.Alsolookontheskulltoobservethe3)laterallycompressedteeth.Theteethofcrocodiliansareverysimilartothoseofthedinosaurs.Crocodiliansarealsocharacterizedby4)atriangulareyeorbit.Crocodilianshaveepidermalscalesthatappear"armor-like"duetothepresenceofosteoderms(adermalbonelocatedunderandsupportinganepidermalscale-butnotpartofthescaleitself).


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IX. Aves-Birds Avesisadiversegroupthatincludesmorethan9,700species.Mostspeciesarespecializedforflight,andeventhosethathaveabandonedflightforstrictlyaquaticorterrestriallifestylesretainthosecharactersthatreadilydistinguishabirdfromothervertebrates.

Birdsaretheonlyvertebratestopossess1)feathers.Onthebodyofthebirdsobserve2)thecontourfeathersthatformthecontourorout-lineofthebird'sbody.Thesefeathershavebeenvariouslymodifiedtoservedifferentfunctions.On3)thewings,thereareseveraltypesoffeathersthatservedifferentpurposes.Observethewingmountstodistinguish4)theprimaryfeathersfrom5)thesecondaryfeathers.Thebases(closetothebone)ofboththeprimaryandsecond-aryfeathersarecoveredby6)thewingcoverts.Whatfunctionsdothesedifferentfeathersserve?Onthetailofthebird,observe7)theretrices.Whatroledotheretricesplayinflight?Howdothetailfeathersofdifferentbirds(e.g.,woodpecker,pheasant)compare?Dependinguponthespecies,timeofyear,andageofthebird,8)downfeatherscanbefoundunderneaththecontourfeathers.Observethedownfeathersondisplay.Whatfunctionsdodownandcontourfeathersserve?

Birdslackteethandhave9)hornybeaksofdifferentsizesandshapes.Birdsarebipedal(walkontwohindlegs).Observetheelongated10)tarsusthatiscoveredwith11)epidermalscales.


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a) Claw–foundinmostamniotes.b) Fingernail–Foundinprimates,includinghumans.c) Hoof–Thetipofthetoefoundinungulates.

X. Mammalia-Mammals Theapproximately5488speciesofmammalsrangeinsizefrom15mlto30m.Mammalsaredividedinto3maingroups:Monotremata(echidnaandplatypus),Marsupialia(marsupials),andEutheria(NewBeast).Thereareseveraldefiningcharacteristicsofmammals,includingthepresenceofmammaryglandsinfemalesthatproducemilkfortheiryoung.

Hair,auniquefeatureofmammals,isanepidermalstructurethathasbeenmodifiedtoservedifferentfunctions,includingthermalregulation.Examinethemammalspecimensandcomparethelengthandtextureofhairs.Onthecoyoteorfoxspecimen,findthe1)underfur,2)guardhairs,and3)vibrissae.Howdothefunctionsofthesehairtypesdiffer?

Thedistalendsofthedigitsofmostmammalspossesseither4)nails,5)claws,or6)hooves.Allarecomposedofafibrousproteincalledkeratin,butdifferinstructureandplacement.Examinethedifferentspecimens(andyourownfingers)todistinguishbetweennails,claws,andhooves.


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Theteethofmostmammalsarehighlymodifiedandveryefficientatgrinding,shearing,andchewingfood.Observetheskullofthecoyoteandthemonkeytodistinguishtheincisors,thecanines,andthemolars.Thetopandbottomteethofmammalsarecloselyaligned,allowingthejawstoclosebringingtheteethtogether.


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Theskullsofmanyungulates(hoofedmammals)areadornedwitheitherantlersorhorns.Examinetheskullsofthedeerandpronghornaswellastheothermammalheadsinlabtoobserveantlersandhorns,respectively.Howdohornsandantlersdifferwithrespecttopermanency(shedannu-allyversuspermanent)andstructure?


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Lab Assignment 1: (10 pts) DichotomousKeytoVertebrateGroups-ExternalFeatures

Eachvertebratelineagepossessesuniquefeaturesthatcanbeusedtoidentifythem.Dichotomouskeysareusefultohelpbiologistsidentifyunfamiliarorganismsandunderstandingtheirevolutionaryrelationships.Usingthekeyexternalcharacteristicsthatdistinguishthedifferentvertebrategroupsobservedinlab,constructadichotomouskeytothefollowingvertebrategroups.

I. MyxinoideaII. PetromyzontoideaIII. ChondrichthyesIV. OsteichthyesV. Amphibia

VI. TestudinataVII. SquamataVIII. CrocodiliaIX. AvesX. Mammalia

Youcanbeginbyusingthelistofcharactersprovided.NOTE:ThislistofcharactersisNOTexhaustive;youwillhavetoincludeothercharacterstodistinguishthevertebrategroupsinyourkey.

Characters:

lowerjawdermalscalesepidermalscalesplacoidscales

ctenoidcycloidscalesheterocercalcaudalfinchoanae

feathersbonyoperculumtympanum

Adichotomouskeyisbasicallyaseriesofpaired,unambiguousquestionsthatcanbeusedtosubdivideagroupoforganisms(orobjects)intouniqueentities.Thetitleofakeywillfirstlimitthegroupoforganismstobeidentified.Forexample,akeytothereptilesinNorthAmericawouldincludeamuchlargergrouptobeidentifiedthanakeytothereptilesofBernalilloCounty.Asyouconstructyoukey,visualizeaprocessdividingtheentiregroupintosmallerandsmallerdivisionsuntileachdivisioncontainsonlyoneentity.Forexample,ifyouhad8objectsof4shapes,differentsizes,andtwocolorsyourkeycouldlooklikethis:


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Itoftenhelpstoconstructadatatableoftheexternalfeaturesthatyouareusing.Belowisanexampleforthegroupsyouarestudyingtoday.

Nameofanimal

Appendage Bodycovering Breathingmechanism

Fins

Four

limbs

Wings

Smoo

th

Skin

Scales

Feathe

rs

Fur

Gills

Lungs

Hagfish Lamprey Chondrichthyes Osteichthyes Amphibia Testudines Squamates Crocodilia Aves Mammals

Keysaredueattheendofthefirstlab.Yourgradeswillbebasedon

1)completeness(doesyourkeydistinguisheachgroup?),

2)conciselogicofkey(doesyourkeydifferentiatebetweenthedifferentgroupsefficiently?),

3)concisedescriptionsofcharactersused,and

4)presentation(isyourkeyneatandinrequestedformat?).

Lab 1 - External Characteristics - POELABGeneral Vertebrate Diversity Lab 1 Lab 1 External...

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