bio 108 topic 26: intro to chordates

What’re chordates

• bilaterian animals that belong to clade deuterostomia

• Bilaterally symmetrical coelomates with segmented bodies

• Most have vertebral backbone

Shared derived traits of chordates

1. Notochord

2. Dorsal, hollow nerve cord

3. Pharyngeal slits or clefts

4. Muscular post anal tail

Expand on notochord

• longitudinal flexible rod bw digestive tube and nerve cord Pharyngeal slits

• Skeletal support

• Forms during embryogenesis

What is the shared derived traits of dorsal, hollow cord

• Nerve cord of chordate embryo developed from a plate of ectoderm that rolls inward to form a neural tube, which is dorsal to notochord

What’re pharyngeal slits or clefts and 3 functions

• grooves in pharynx in chordates

• Allows water entering mouth to exit through slits

• Suspension feeding

• Gas exchange

What is the trait of muscular post-anal tail

• common in most adult chordates

• Tail contains skeletal elements and muscle

• Tail is greatly reduced during embryonic development

Lancelets

• marine suspension feeders that retain traits of the chordate body plan as adults

  • Wriggle backwards into sand

  • Water exits body thro atropore

• Subphylum Cephalchordata

Tunicates

• subphylum Urochordata

• closely related to other chordates than are to lance let’s

• Most resemble chordate body plan during larval stage

• As adults tunicate draws in water thro siphon

• Sessil

• Sea squirts (shoot water) when attacked

• Can reproduce asexually by budding