Chordates Name:_________________________________________Class:__________Date:____________Vocabulary

Term Definition

chordate Animalwithanotochord,dorsalhollownervecord,post-analtail,andpharyngealslitsduringatleastsomestageofitslife.

dorsal hollow nerve cord Hollowcordabovethenotochord;sometimesincludesabrainandspinalcord.

notochord Supportrodthatrunsalongtheback.pharyngeal slit Organthataidsinfilter-feeding.post-anal tail Tailthatisoppositetheheadandextendspasttheanus.

What do these two animals have in common with you? Noticetheorangefish.Aroundhimisanothertypeofanimal,atunicate,inblue.Tunicates,fish,andhumansseemverydifferentfromoneanother,buttheydohavesomethingsincommon.Theyareallchordates.Chordates Didyouknowthatfish,amphibians,reptiles,birds,andmammalsareallrelated?

Theyareallchordates.Chordatesareagroupofanimalsthatincludesvertebrates,aswellasseveralcloselyrelatedinvertebrates.Chordates(phylumChordata)arenamedafterafeaturetheyallshare,anotochord.Anotochordisahollownervecordalongtheback.Characteristics of the Chordates Chordatesaredefinedbyasetoffourcharacteristicsthataresharedbytheseanimalsatsomepointduringtheirdevelopment.Insomechordates,allfourtraitsarepresentintheadultanimalandserveimportantfunctions.However,inmanychordates,includinghumans,sometraitsarepresentonlyduringtheembryonicstage.Afterthat,thesetraitsmaydisappear.Allchordateshavefourmaintraits:

1. Post-analtail:Thetailisoppositetheheadandextendspasttheanus.2. Dorsalhollownervecord:"Dorsal"meansthatthenerve

cordrunsalongthetopoftheanimal.Insomeanimals,thenervecorddevelopsintothebrainandspinalcord.

3. Notochord:Thenotochordliesbelowthenervecord.Itisarigidstructurewheremusclesattach.

4. Pharyngealslits:Pharyngealslitsareusedtofilteroutfoodfromwaterbysomesimplechordates.Inmostchordates,however,theyareonlypresentduringtheembryonicstagesandservenoapparentpurpose.

Classification of the Chordates Thechordatesaredividedintonineclasses.Fiveoftheclassesarethefish,amphibians,reptiles,birds,andmammals.Thereareactuallyfiveclassesofmarinechordates(forexample,sharksarecartilaginousfishwhicharedistinctfrombonyfish),andthesewillbediscussedinadditionalconcepts.Thechordatephylumisbrokendownintothreesubphyla:

• Urochordata:Thetunicates,picturedintheintroduction,makeupthisgroup.Theurochordatesaresessile(non-moving)marineanimalswithsack-likebodiesandtubesforwatermovement.Urochordateshaveanotochordandnervecordonlyduringthelarvalstage.

• Cephalochordata:Cephalochordatesincludethelancelets,fish-likemarineanimalsoftenfoundhalf-buriedinthesand.Cephalochordateshaveanotochordandnervecordbutnobackbone.

• Vertebrata:Humansandothermammals,alongwithfish,amphibians,reptiles,andbirds,fallinthiscategory.Invertebrates,thenotochordistypicallysmallerandsurroundedbyabackbone.

Summary

• Chordatesareanimalsthathaveanotochord,post-analtail,dorsalhollownervecord,andpharyngealslits.

• Chordatesincludeallvertebratesandsomeinvertebrates. Review

1. Whatisthemaincommonfeatureofallchordates?

2. Nameanddescribethreeexamplesofchordates.

3. Listandexplainthreecharacteristicsofchordates.

4. Whatisthedorsalhollownervecord?