Animals 4 - CHORDATA *Urochordata *Cephalochordata *...

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CHORDATA *Urochordata *Cephalochordata * CRANIATA *Vertebrata Craniate advancements Two clusters of HOX genes Other gene families (that produce signaling molecules and transcription factors) also duplicated Neural crest Neural crest cells give rise to: Teeth Some bones in the skull (e.g., jaw bones) The dermis of the face Several types of neurons Sensory capsules in which eyes and some other sense organs develop See Fig. 34.7
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Hagfishes: craniates, without a vertebral column Fig. 34.2, page 672 Lampreys: jawless craniates, possessing vertebrae KEY innovations
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Fig. 34.13 The evolution of jaws Gnathostomes show additional duplication of HOX and other major regulatory genes; the brain enlarged, esp. giving better senses of smell and sight. The coelacanth, a lobefin fish What assisted the evolution of legs? Freshwater aquatic environments were becoming more varied – rivers, lakes, wetlands Land plants (including aquatic forms) were abundant in freshwater habitats, providing a source of fixed carbon
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Animals 4 - CHORDATA *Urochordata *Cephalochordata *...

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