Chapter 34 Vertebrates

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Chapter 34 Vertebrates

• Barbara Musolf
• Clayton State University
• AS Building G 110-G
• 678-466-4851

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Objectives

• Know the chordate characteristics
• Notocord
• Dorsal hollow nerve cord
• Pharyngeal basket
• Post-anal tail

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Fig. 34.2)
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Origin of backbones

• A slender 2 cm slender marine organism gave rise
  to vertebrates 500 million years ago
• Vertebrates were restricted to the ocean for 200
  million years
• 360 million years ago they moved to land
• Vertebrates gave rise to the largest and heaviest
  organisms (plant-eating dinosaurs) to walk on
  land and the largest that exists in the ocean
  (Blue whale).
• Vertebrates produced an organism with language,
  complex tool-making skills and symbolic thinking.

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Chordata (Fig. 34.4)

• Bilaterian deterostomes
• Derived characteristics
• Presence of a notocord
• Dorsal hollow nerve cord
• Pharyngeal gill slits
• Muscular post-anal tail

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Cephalochordata

• Lancelet adults have all 4 chordate
  characteristics
• Segmentation appears as somites
• Feed by swimming up into the water column and
  then trap plankton in their pharynx as they sink.

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Urochordata

• Tunicates descend from the earliest branch of the
  chordate tree.
• Characteristics of chordates are evident in the
  larva
• Adult tunicates are sessile and lack chordate
  structures such as notocord and tail
• Protect themselves by shoot a jet of water from
  its excurrent siphon.

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Urochordatetunicate (Fig. 34.4)
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Early chordate evolution (Fig. 34.6)

• The Hox genes in lancelet that organize the
  anterior-posterior development of the nervous
  system are similar to vertebrates