Animal diversity – the chordates

Animal diversity the chordates

Animal diversity the chordates

Chordate CharacteristicsNotochord

Dorsal, hollow nerve cord

Gill slits

Tail Modern Chordate Groups

Invertebrate ChordatesLancelets are the only group of chordates that retains all chordate characteristics as adults.

4Invertebrate ChordatesTunicates have typical chordate larvae, but adults retain only the pharynx with gill slits

CraniatesCraniates have a braincase of cartilage or bone (cranium) that encases the brain, paired eyes, and other sensory structures on the head

Craniates includes fishes, amphibians, reptiles, birds, and mammals

Hagfishes are the only modern craniates that are not vertebratesHagfishes (Class Myxini)Soft bodied, boneless fishes

Squidoo. 2011. http://www.squidoo.com/eelskin-wallets

Squidoo. 2011. http://www.squidoo.com/eelskin-walletsIs that a hagfish purse or an eel-skin purse?

Chordate Family Tree

Vertebrate Traits and TrendsEndoskeletonVertebral columnJawsPaired fins or appendagesGills or lungsClosed circulatory systemOther organ systems

Vertebrates have backbonesEmbryonic notochord eventually replaced by a vertebral columnVertebral column composed of bone or cartilageVertebral column functionsPossess living internal skeleton that has allowed great size and mobilityThe Major Vertebrate GroupsJawless fishesJawed fishesAmphibiansReptiles and birdsMammals

Jawless fishesEarliest vertebrates lacked jawsEarly vertebrates were jawless fishes (extinct) whose bodies were protected by bony armor plates

Jawless fishesLampreys (Class Petromyzontidae)Represents distinct early branch of chordate evolutionary treeHas large round sucker that surrounds mouthSingle nostril on top of headNerve cord of lampreys protected by segments of cartilageMay be parasitic or nonparasiticParasitic-have rasping teeth on tongue which it uses to grasp hostWill burrow through body wall in order to feast on blood and body fluids

Lampreys

Sea lamprey - parasiticFreshwater lamprey - nonparasitic

Jawed fishesHave Jaws! important adaptationEarliest jawed organisms were fishBenefits of jawsAllow to grasp, tear, or crush foodCould exploit more food sourcesGave rise to the cartilaginous fishes, ray-finned fishes, lobe-finned fishes

Early Jawed Fishes - Placoderms

UC Berkeley. 2011. http://www.ucmp.berkeley.edu/vertebrates/basalfish/placodermi.html

BHC. 2009. http://facweb.bhc.edu/academics/science/harwoodr/geol102/Study/Images/Placoderm.jpg