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Chapter17
Chordata:UrochordataandCephalochordata
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PhylumChordata
• Characteris;cs1. Bilaterallysymmetricaldeuterostomes2. Auniquecombina;onof5characteris;cs:
1. notochord2. pharyngealslitsorpouches3. dorsaltubularnervecord4. postanaltail5. endostyleorthyroidgland
3. Completediges;vetract4. Ventral,contrac;lebloodvessel(heart)
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PhylumChordata
• Notochord- Suppor;ve,flexibleroddorsaltobodycavity- Connec;ve;ssuesheath
• Pharyngealslits- Openingsbetweendiges;vetractandoutsideofbody- Maybeinformofpouches- Filterfeedingor,insome,gillsdevelopforgasexchange
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Figure17.2Chordatebodyplan.
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PhylumChordata
• Tubularnervecord– Dorsaltonotochord– Expandedanteriorlyintobrain
• Postanaltail– Extendsposteriorlybeyondanalopening
• Endostyle(orthyroidgland)– Ventralaspectofpharynx– Secretesmucususedinfilterfeeding– Transformedintothyroidglandinadultlampreysandotherchordates
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SubphylumUrochordata
• Tunicatesorseasquirts– Ascidians(seasquirt)sessileasadults– Appendiculariansandthaliaceansplanktonicasadults
– Thaliaceans(salps)arebioluminescent
• Bodywallcoveredbyconnec;ve-;ssuetunic
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SubphylumUrochordataFigure17.3SubphylumUrochordata.
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Figure17.4TunicateMetamorphosis.
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SubphylumUrochordata• Maintenancefunc;ons
– Nervoussystem• Nervesinbodywall• Singlegangliononpharynx
– Nocomplexsensoryorgans– Feedinganddiges;on
• Ciliary-mucousmechanism• Endostylesecretesmucoussheet• Diges;vewasteexitswithexcurrentwater
– Gasexchange• Pharynx
– Circula;on• Heartatbaseofpharynx• Amoeboidcellsaccumulatenitrogenwaste
– Excre;on• DiffusionandreleasewithexcurrentwaterCopyright©2016McGraw-HillEduca;on.Allrightsreserved.Noreproduc;onordistribu;onwithoutthe
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Figure17.5Internalstructureofatunicate.
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SubphylumUrochordata
• Reproduc;onanddevelopment– Monoecious– Externalfer;liza;onorwithinatrium– Tadpole-likelarvase`lesandundergoesmetamorphosis(figure17.4).
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SubphylumCephalochordata
• Lancelets• Shallowmarinesubstrates• Par;allyburiedfilterfeeders• Notochordextendsintohead• Segmentallyarrangedmusclesoneithersideofnotochord
• Oralhoodwithcirri
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Figure17.6SubphylumCephalochordata.
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SubphylumCephalochordata
• Maintenancefunc;ons– Filterfeeding
• Ciliatedgillbarscreatewatercurrents• Cirrisortfood• Endostylesecretesmucusthattrapsfoodongillbars• Transportedtogut
– Circula;on• Contrac;lewavesinvesselspropelblood
– Excre;on• Excretorytubulesreceivewastefromblood
– Coelomreduced
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SubphylumCephalochordata
• Reproduc;onanddevelopment– Dioecious– Free-swimminglarvaese`leandmetamorphosetoadults
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FurtherPhylogene;cConsidera;ons
• Deuterostomata– Echinodermata,Hemichordata,Chordata– Molecular,morphological,anddevelopmentalevidencepointtothechordatesasmonophyle;c
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Figure17.7OneInterpreta;onofDeuterostomatePhylogeny.
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FurtherPhylogene;cConsidera;ons
• ThirdchordatesubphylumisCraniata– InfraphylumVertebrata• Largestandmostsuccessfulchordates• Bonyorcar;laginousvertebraecompletelyorpar;allyreplacenotochord• Three-partbrain• Skeletonmodifiedintoskullorcranium• Abundantfossilrecord• Chapters18-22
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AnatomicalTerms
• Anterior• Posterior• Dorsal• Ventral• Lateral• Medial• Caudal
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