L20. Basal Chordata

Chordata: origins and body plan

Basic Chordate Body Plan4 major features of Chordata

notochorddorsal hollow nerve

pharyngeal slits post-anal tail

Basic Chordate Body Plan4 major features of Chordata

notochorddorsal hollow nerve

pharyngeal slits post-anal tail

These are synapomorphies for chordates

Urochordata: tunicates

Urochordates show chordate characters in the larva

1. Notochord2. Dorsal hollow nerve3. Pharyngeal slits

Urochordate Larvae

very young larva

late larvalstage

Cephalochordata:lancelets

notochord dorsal hollow nerve

many pharyngeal slits

Cephalochordatatail cross-section

dorsal hollow nerve

notochord

Hemichordata

Hemichordate

1.

2.

3.

1. Pharyngeal slits2. Dorsal hollow nerve, notochord3. Postanal tail, neural crest cells, vertebrae

Major Groups of chordates we will visit in coming lectures Trends in early Chordate & Vertebrate Evolution

1. Increased cephalization2. Increased activity levels3. Increased tendency toward predatory life-style

Lamprey Larval Lamprey

Vertebrate Body Plan

1. Notochord2. Dorsal hollow nerve, brain, eyes3. Paired kidneys4. Pharyngeal slits5. Heart, aortic arches, dorsal aorta6. Segmented body organization

Vertebrate Body Plan

Lamprey: bloodsucking basal vertebrate!!

-No bone, no jaws-Has pharyngealslits, notochord,dorsal hollow nerve,post-anal tail

Hagfishes: scavengers on dead animal carcasses

-No bone, no jaws-Has pharyngeal slits, notochord,dorsal hollow nerve, post-analtail