Download Lab 1 External Characteristics of Vertebrates

GeneralVertebrateDiversityLab
Lab 1
External Characteristics of Vertebrates
Objectives
1. Listthemajorgroupsofvertebrates.
2. Describethedefiningcharacteristicsofvertebrates.
3. Useexternalcharacteristicstodistinguishbetweenthemajorvertebrategroups.
Introduction
Vertebratesareauniquelineageoforganismsthatdescendedfromacommonancestordating
backtheCambrianover500millionyearsago.Today,allvertebratespossesscertain
characteristicsinheritedfromthatcommonancestor.Overtime,vertebrateshaveevolvedinto
multiplelineages,eachwithuniquederivedcharacters.Asyouworkthroughthislab,observe
thesimilaritiesanddifferencesbetweenthesevertebrategroups.
Jawless Fish - Agnatha
I.
Myxinoidea – Hagfish
Hagfisharejawlessscavengersthatfeedupondyinganddeadfishesandwhales.There
are75knownspeciesofhagfish,allfoundinmarineenvironments.Examinethespecimenof
thehagfishandbeabletolocateandknowthefunctionofthelabeledstructures.
1. Slimeglands,whichoccuroneachside,onepersegment.Slimeglandsareoftenmost
evidentintheposteriorregion(butcanbehardtosee).
2. Externalgillopenings.Gillslitsvaryinnumberfrom1-15pairs.
3. Oraltentaclesorbarbels.Whatmightbethefunctionoftheseoraltentacles?
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GeneralVertebrateDiversityLab
II.
Petromyzontoidea - Lamprey
Theapproximately40speciesofjawlesslampreysrangeinsizefrom25cmtoabout1
meter.Manyspeciesareborninfreshwater,spending5ormoreyearsinalarvalformbefore
theymetamorphoseintoadultformandmigratetomarinehabitats.Somespeciesarefound
exclusivelyinfreshwater.Manyspecies,includingthespecimensinlab,areparasitic.Theycan
beseenattachedtotheoutsideoftheirhosts,whichareoftenotherfishes.
Thebodycanbedividedintothreeregions:
1) Head(extendingthroughthegillarea)
2) Trunk(gillsto)cloaca),
3) Tail(posteriortocloaca).
Observethetwodorsalfinsandcaudalfin.Atthefrontofthehead,observethebuccal
tunnelthatisfringedwithpapillaeandlinedwithhornyteeth.Asingle,mediannostrilis
locatedfarbackonthetopofthehead.Justbehindthenostrilisthepinealeyeorcornea.Itis
anovalareathatisoftenslightlydepressedandgenerallyalightercolorthantherestofthe
skin.Onthesidesoftheheadisapairoflidlesseyes.Behindtheeyesarelocatedsevenpairsof
externalgillslits.
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Gnathostome – Jawed Fishes
III.
Chondrichthyes-Cartilaginous fish/Sharks
Sharksandrays(Elasmobranchii)andratfishes(Holocephali)aremembersofthetaxon
Chondrichthyes,whichincludesover900species.Allbut28speciesarefoundinmarine
habitatsandmostarepredatorycarnivores(thoughseveralfeedonplankton).Examinethe
dogfishsharkspecimensandthemicroscopeslidestoidentifyandlearnthegeneral
functionofthelabeledstructures.Thebodyisdividedintothehead,trunk,andcaudal
regions.
Ontheheadlocate:
1)
2)
3)
4)
Themouth,
Theeyes,
Thespiracles,
Thenostrils(eachofwhichis
partiallysub-dividedbyaflap
ofskinthatSeparatesthe
streamofwaterflowinginto
andoutofthenostril)
Onthetrunkofthesharklocate
5) TheampullaeofLorenzini
6) Externalgillslits,Formingthe
divisionbetweenthehead
andtrunkarethe.Howmany
pairsofgillslitsdoesthe
dogfishsharkpossess?
7) Thepairedpectoralfins
8) Pelvicfins.Thepelvicfinswillvarybetweenthemalesandfemales.Maleswill
havestiff,groovedcopulatoryorganscalledclaspersonthemedialsidesofthe
pelvicfins.AllChondrichthyeshaveinternalfertilizationanddevelopment.
9) Anteriordorsalfin.Thedorsalfinhasalargespineinfrontofit,whichis
defensive.
10) Thelaterallineisfoundalongthesidesofthebodylookforafine,light-colored
stripethatis.
11) Placoidscales.Notetheroughnessoftheskinwhenyourunyourfingersfrom
theposteriortotheanteriorend.Howdoesthestructureofthescalesofshark
resembleatooth?
14) Thetailendsinthelarge
heterocercalcaudalfin.Note
howthebodyaxisturnsup
intothedorsallobeofthe
caudalfin.
Onthetailendofthesharklocate
12) Thecloacaformsthedivision
betweenthetrunkandtailof
theshark.
13) Onthedorsalsideofthetail
istheposteriordorsalfin
withaspine.
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12.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
Anteriordorsalfin
DorsallobeofCaudalfin
Endolymphaticpores
Excurrentapertureofnaris
Externalgillslits
Externalnaris
Externalspiracularpore
Eye
lncurrentapertureofnaris
Lateralline
Lowereyelid
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
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MucousporesofAmpullaeof
Lorenzini
Nasalflap
Pectoralfin
Pelvicfin
Placoidscales
Posteriordorsalfin
Eye
Snout
Spineofdorsalfin
SpiracularvalvewithPseudo-branch
onposteriorwall
Uppereyelid
VentrallobeofCaudalfin
GeneralVertebrateDiversityLab
IV. Osteichthyes - Bony fish
Osteichthyesisthemostdiversegroupofvertebrates(ca.26,000-30,000species)andincludes
twomajorgroups:Actinopterygii,theray-finnedfishes,andSarcopterygii,thelungfishesand
thecoelacanth.InlabwewillfocusontheActinopterygii.Actinopterygianfisheshavefinsthat
aresupportedentirelybydermalfinrays.ThedifferentgroupsofActinopterygianfishesare
differentiatedbyanumberofexternalcharactersincludingtypeofcaudalfin(heterocercalor
homo-cercal)andtypeofscale(ganoid,ctenoid,cycloid).Ingeneral,themoreprimitive
Actinopterygiipossessaheterocercaltailandganoidscalesandthemorederivedlineages
possesshomocercaltailsandcycloidorctenoidscales.Examinethespecimensandmicroscope
slidestolocateanddescribethegeneralfunctionofthelabeledstructures.
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.).Observethe
perchspecimens.Thebodyisdividedintothehead,trunk,andtail.
Nostril
Spinydorsalfin
Operculum
SoftDorsalFin
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Onthehead,locatethepositionof
3)
4)
5)
6)
Themouth.
Thenostrils
Eyes(notehowtheyprotrudefromthesidesofthefish).
Theoperculum.
Onthetrunkofthefishlocate
7) thepairedpectoralfins
8) Pelvicfins.
9) Theanteriorandposteriordorsalfins.
10) Thelateralline.
11) Thetrunkendsatthecloaca.
12) Thecaudalfinthatislocatedattheendofthehomocercaltail.Thevertebralcolumn
doesnotextendintotailcaudalfin.
13) Themoreadvancedbonyfisheshaveeithercycloidorctenoidscales.Thesearethinand
flexibleandarearrangedinoverlappingrows.Examinetheexamplesofcycloidand
ctenoidscalesunderthemicroscope.
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GeneralVertebrateDiversityLab
Cycloidscalesaretypicallycircularinnature.Thescalesgrowinconcentriclayersandhavea
smoothoutermargin.Theyarefoundinthemorederivedray-finfish,theteleost.
Cycloidscalesarefoundoftenfoundinfishwithsoftrays,includingthisRiverCarpsucker(Carpoidescarpio).
Ctenoidscalesareoftenfoundinfishwithspinyfinrayslikethisgreensunfish(Lepomiscyanelis)
Ctenoidscalesresemblecycloidscales,excepttheyhavesmallteethontheirouteredges.
Similartocycloidscales,theyalsogrowinconcentriclayersandarefoundinteleost
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GeneralVertebrateDiversityLab
GanoidScalesaretypicallythickandnotoverlappingandconnectedbypeg-and-socketjoints.
Theyarefoundinnon-teleostray-finnedfish(gars,bichirs,bowfins,andsturgeons,and
paddlefish).Ingars,thescalesaregreatlyenlargedtoformarmorplates.
PlacoidscalesarefoundintheChondrichthyesorcartilaginousfishincludingthesharks,
skates,andrays.Placoidscalesarebasicallyminiatureteeth,possessingpulpsuppliedbyblood
vessels,surroundedbyalayerofdentine.Asthefishgrowsinsize,morescalesareadded.
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GeneralVertebrateDiversityLab
Tetrapods
V. Amphibia-Amphibians
Amphibiansareanancientlineagedatingbackto370millionyearsago.Allmodernamphibians
areclassifiedastheLissamphibia,whichincludesabout7,000extantspeciescomprising3main
groups:Gymnophiona(caecilians),Anura(frogs),andUrodela(salamanders).Sharedexternal
characteristicsforthesegroupsinclude1)skinthatisspecializedforgasexchangeandpossess
poisonglands,and2)forelimbswith4digits(frogsandsalamanders).Inlab,wehavespecimens
offrogs,salamanders,andcaecilians.
Gasexchangethroughtheskinisveryimportantforamphibiansallowingthemtoremain
submergedforextendedperiodsoftime.Itsfunctionisdependentupontheproximityofblood
capillariestothesurfaceandamoistskinsurface.Moistskinismaintainedbythepresenceof
manymucousglandsintheskin.Poisonglandsintheskinproducenoxiousortoxicsubstances
usedindefenseagainstpredation.
Theeggsofamphibianslackshellsandmustdevelopinamoistenvironment.Many(butnotall)
amphibiansgothroughalarvalstage.Someamphibiansretainlarvalfeaturesintosexual
maturity;thisiscalledneoteny.Observethegillsofthemudpuppy
Amphibiansarethemostprimitiveofthelivingtetrapods.Observe4)forelimbswith4digits
(fingers)oneachand5)thehindlimbs.Observethedifferencesinlimbstructurebetweenthe
salaman-dersandfrogs.Howhavethelimbsofthelatterbeenmodified?Observe6)thetailof
themudpuppy(Necturus).Anuranslackatail.Alltetrapods(aswellasthelungfish)possess
choanaeorinternalnares.Usingtheprobepro-vided,gentlyexaminethe7)nostrilsofthefrog.
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GeneralVertebrateDiversityLab
Observetheeyesofthefrogandlocatetheclear8)nictitatingmembrane.Behindtheeye,
locatetheround9)tympanicmembrane.Doesthemudpuppyhaveanictitatingmembraneor
tympanicmembrane?
Amniotes
VI. Testudinata-Turtles
Testudinataincludesabout327speciesofextantturtlesthatarefoundinterrestrial,
freshwater,andmarinehabitats.Therearetwogroupsofturtles:Cryptodiraincludesabout200
speciesandPleurodiraabout50species.Thegroupsaredistinguishedbythewaytheyretract
theirheadsintotheirshells.Cryptodiresretracttheirheadsintotheirshellsbybendingtheir
necksinaverticalS-shape;pleurodiresretracttheirheadsbybendingthenecklaterally.
CryptodiresaretheonlyturtlesinNorthAmerica.Turtlesareuniqueinthatthepelvicand
pectoralgirdlesarelocatedbehindtheribcage.
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GeneralVertebrateDiversityLab
Examinethespecimenoftheturtle.Theshelloftheturtleisdividedintothedorsal1)carapace
andtheventral2)plastronThecarapaceandplastronareconnectedby3)thebridge.
VII. Lepidosauria-Squamata-Lizards/Snakes
Squamataincludestheapproximately9,000speciesoflizardsandsnakes.Onesharedcharacter
oflizardsandsnakesisthepresenceofhemipenes(dualcopulatoryorgans)inmales.Although
snakeslackexternalpairedappendagestheyareconsideredtetrapodsbecausetheirancestors
possessedlimbsandbecausetheskeletonsofsomesnakesstillhavevestigial(veryreduced)
girdles.Limbreductionhasevolvedrepeatedlyamonglizards,perhapsasmanyas62times.As
youexaminethespecimensofthelizardsandsnakesobserveboththesimilaritiesand
differences.
Allsquamatespossess1)epidermalscales.Examinethedifferentlizardandsnakespecimensto
seehowtheshapesandsizesoftheepidermalscalescanvary.Examinethe2)eyesofthe
lizardsandsnakes.Mostlizardshavemoveableeyelidswhereastheeyesofsnakesarecovered
withatransparentcap.Lookbehindtheeyesofboththesnakeandthelizard,onwhichonedo
yousee3)anexternalearslit?
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GeneralVertebrateDiversityLab
VIII. Crocodilia-Alligators/Crocodiles
Thereare23speciesofcrocodiliansinthreegroups(Alligatoridae,Crocodylidae,Gavialidae).
Thesegroupsaredistinguishedbythesnoutshape.
Examinethealligatorskullandobservetheelongatesnoutwith1)nostrilsonthedorsaltipof
snout.Thenostrilsonthedorsaltipofthesnoutcombinedwithacompletesecondarypalate
(likemammalshave)allowcrocodilianstobreathewhenthemouthisunderwater(orfullof
food).Lookattheskulltoseethe2)secondarypalate.Alsolookontheskulltoobservethe3)
laterallycompressedteeth.Theteethofcrocodiliansareverysimilartothoseofthedinosaurs.
Crocodiliansarealsocharacterizedby4)atriangulareyeorbit.Crocodilianshaveepidermal
scalesthatappear"armor-like"duetothepresenceofosteoderms(adermalbonelocated
underandsupportinganepidermalscale-butnotpartofthescaleitself).
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GeneralVertebrateDiversityLab
IX. Aves-Birds
Avesisadiversegroupthatincludesmorethan9,700species.Mostspeciesarespecializedfor
flight,andeventhosethathaveabandonedflightforstrictlyaquaticorterrestriallifestyles
retainthosecharactersthatreadilydistinguishabirdfromothervertebrates.
Birdsaretheonlyvertebratestopossess1)feathers.Onthebodyofthebirdsobserve2)the
contourfeathersthatformthecontourorout-lineofthebird'sbody.Thesefeathershavebeen
variouslymodifiedtoservedifferentfunctions.On3)thewings,thereareseveraltypesof
feathersthatservedifferentpurposes.Observethewingmountstodistinguish4)theprimary
feathersfrom5)thesecondaryfeathers.Thebases(closetothebone)ofboththeprimaryand
second-aryfeathersarecoveredby6)thewingcoverts.Whatfunctionsdothesedifferent
feathersserve?Onthetailofthebird,observe7)theretrices.Whatroledotheretricesplayin
flight?Howdothetailfeathersofdifferentbirds(e.g.,woodpecker,pheasant)compare?
Dependinguponthespecies,timeofyear,andageofthebird,8)downfeatherscanbefound
underneaththecontourfeathers.Observethedownfeathersondisplay.Whatfunctionsdo
downandcontourfeathersserve?
Birdslackteethandhave9)hornybeaksofdifferentsizesandshapes.Birdsarebipedal(walk
ontwohindlegs).Observetheelongated10)tarsusthatiscoveredwith11)epidermalscales.
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GeneralVertebrateDiversityLab
X. Mammalia-Mammals
Theapproximately5488speciesofmammalsrangeinsizefrom15mlto30m.Mammalsare
dividedinto3maingroups:Monotremata(echidnaandplatypus),Marsupialia(marsupials),
andEutheria(NewBeast).Thereareseveraldefiningcharacteristicsofmammals,includingthe
presenceofmammaryglandsinfemalesthatproducemilkfortheiryoung.
Hair,auniquefeatureofmammals,isanepidermalstructurethathasbeenmodifiedtoserve
differentfunctions,includingthermalregulation.Examinethemammalspecimensandcompare
thelengthandtextureofhairs.Onthecoyoteorfoxspecimen,findthe1)underfur,2)guard
hairs,and3)vibrissae.Howdothefunctionsofthesehairtypesdiffer?
Thedistalendsofthedigitsofmostmammalspossesseither4)nails,5)claws,or6)hooves.All
arecomposedofafibrousproteincalledkeratin,butdifferinstructureandplacement.Examine
thedifferentspecimens(andyourownfingers)todistinguishbetweennails,claws,andhooves.
a) Claw–foundinmostamniotes.
b) Fingernail–Foundinprimates,includinghumans.
c) Hoof–Thetipofthetoefoundinungulates.
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GeneralVertebrateDiversityLab
Theteethofmostmammalsarehighlymodifiedandveryefficientatgrinding,shearing,and
chewingfood.Observetheskullofthecoyoteandthemonkeytodistinguishtheincisors,the
canines,andthemolars.Thetopandbottomteethofmammalsarecloselyaligned,allowing
thejawstoclosebringingtheteethtogether.
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GeneralVertebrateDiversityLab
Theskullsofmanyungulates(hoofedmammals)areadornedwitheitherantlersorhorns.
Examinetheskullsofthedeerandpronghornaswellastheothermammalheadsinlabto
observeantlersandhorns,respectively.Howdohornsandantlersdifferwithrespectto
permanency(shedannu-allyversuspermanent)andstructure?
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GeneralVertebrateDiversityLab
Lab Assignment 1: (10 pts)
DichotomousKeytoVertebrateGroups-ExternalFeatures
Eachvertebratelineagepossessesuniquefeaturesthatcanbeusedtoidentifythem.
Dichotomouskeysareusefultohelpbiologistsidentifyunfamiliarorganismsandunderstanding
theirevolutionaryrelationships.Usingthekeyexternalcharacteristicsthatdistinguishthe
differentvertebrategroupsobservedinlab,constructadichotomouskeytothefollowing
vertebrategroups.
I.
Myxinoidea
VI.
Testudinata
II.
Petromyzontoidea
VII.
Squamata
III.
Chondrichthyes
VIII.
Crocodilia
IV. Osteichthyes
IX.
Aves
V.
Amphibia
X.
Mammalia
Youcanbeginbyusingthelistofcharactersprovided.NOTE:ThislistofcharactersisNOT
exhaustive;youwillhavetoincludeothercharacterstodistinguishthevertebrategroupsin
yourkey.
Characters:
lowerjaw
dermalscales
epidermalscales
placoidscales
ctenoid
cycloidscales
heterocercalcaudalfin
choanae
feathers
bonyoperculum
tympanum
Adichotomouskeyisbasicallyaseriesofpaired,unambiguousquestionsthatcanbeusedto
subdivideagroupoforganisms(orobjects)intouniqueentities.Thetitleofakeywillfirstlimit
thegroupoforganismstobeidentified.Forexample,akeytothereptilesinNorthAmerica
wouldincludeamuchlargergrouptobeidentifiedthanakeytothereptilesofBernalillo
County.Asyouconstructyoukey,visualizeaprocessdividingtheentiregroupintosmallerand
smallerdivisionsuntileachdivisioncontainsonlyoneentity.Forexample,ifyouhad8objects
of4shapes,differentsizes,andtwocolorsyourkeycouldlooklikethis:
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GeneralVertebrateDiversityLab
Itoftenhelpstoconstructadatatableoftheexternalfeaturesthatyouareusing.Belowisan
exampleforthegroupsyouarestudyingtoday.
Hagfish
Lamprey
Chondrichthyes
Osteichthyes
Amphibia
Testudines
Squamates
Crocodilia
Aves
Mammals
Gills
Fur
Feathers
Scales
Smooth
Skin
Wings
Four
limbs
Fins
Nameof
animal
Breathing
mechanism
Bodycovering
Lungs
Appendage
Keysaredueattheendofthefirstlab.Yourgradeswillbebasedon
1)completeness(doesyourkeydistinguisheachgroup?),
2)conciselogicofkey(doesyourkeydifferentiatebetweenthedifferentgroupsefficiently?),
3)concisedescriptionsofcharactersused,and
4)presentation(isyourkeyneatandinrequestedformat?).
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