DIVERSITY, CLASSIFICATION & EVOLUTION PART III VERTEBRATE ZOOLOGY (VZ Lecture03 – Spring 2012 Althoff - reference PJH Chapters 1,2 & 7)

Two Embryonic Features that may account for difference between vertebrates and other chordates  In vertebrates: development of tissue called ______________. Forms many new structures found only in vertebrates  Duplication of the ______________________

chicken embryo I – migrates to form mandible II—migrates to form hyoid apparatus III & IV—migrate to form outflow tract of heart _______________ “migrating” to branchial arches 1

Neural Crest Cells Originally thought that neural crest was derived from ectoderm germ layer Recently (Hall 2000) proposed that neural crest actually is a truly “independent germ layer”—not part of ecto-, endo-, or mesoderm. If true…. Vertebrates are the only animals that have __ germ layers making them ____________ Helps explain significant advancement in variety of structures in “true” vertebrates 1

Hox gene complex = Homeobox genes that characterize animals Don’t code for specific features, but regulate expression of the hierarchy of other genes that control the shape of the body Jellyfishes – 1 or 2 Hox genes Echinoderms & Nonvertebrate Chordates —7 up to 13 vs. Vertebrates which have undergone ___________ of entire Hox complex 2

Hox gene complex…con’t So, what is the minimum number of Hox genes in vertebrates? Likely ____ Mammals appear to have ____ such genes Bottomline: “More complex animals usually have a greater amount of genetic material…and it is thought that the ________ of this gene sequence at the _______ of vertebrate evolution made possible the evolution of a more complex type of animal” Pough, Janis, & Heiser 2005

Early History & Vertebrate Evolution Vertebrates first appeared in the early Paleozic, about 540 MYA….earth at the time was mostly water covered, extensive continental movements, and an O 2 rich atmosphere formed as a result of ________________________ of autotrophs Movement of land masses and climatic differences/changes resulted in major evolutionary effects on vertebrates. WHY?

Early History: PALEOZOIC Vertebrates first appeared in the early Paleozoic, about ~________….earth at the time was mostly water covered, extensive continental movements, and an O 2 rich (in relative terms) atmosphere. 490 MYA  443 MYA many shallow seas appeared, allowed for major radiation among marine animals, followed by first appearance of primitive vertebrates—primarily _____________, followed by _______________

Early History: PALEOZOIC…con’t 443  417 MYA vascular plants and arthropods just starting to appear, Jawless fishes continued to radiate and jawed fishes (including sharklike forms) appeared 417  354 MYA major freshwater basins appeared with first tetrapods. End of this period marked by disappearance of ________________ ____________ (ostracoderms) 354  290 MYA major glaciation. First appearance of ___________ and modern types of jawless fishes. Extensive radiation of non- amniote tetrapods. First __________ appeared.

Early History: PALEOZOIC…con’t 290  251 MYA Single continent (Pangea) formed near end of this period. -largest non-amniote tetrapods declined -amniotes radiated  modern reptiles mammal-like reptiles first known ___________ tetrapods Largest known ______________ event occurred at end of period—impacting both land and sea fauna: THE END OF THE PALEOZOIC

MESOZOIC 251  206 MYA Single continent high, few shallow seas, no evidence of glaciation mammal-like reptiles declined archosaurian reptiles (including dinosaur ancestors) diversified all large nonamniote tetrapods now aquatic forms true mammals appear dinosaurs, pterousaurs, marine reptiles, crocodiles, lepidosaurs, frog-like amphibians, and teleost fishes appear 206  144 MYA Continent breakup. Modern sharks and rays appear. _________________________________

PALEOZOIC (late Carboniferous Period) Aquatic nonamniote tetrapods Terrestrial nonamniote tetrapods Fig. 7-5 p165 PJH