Transcript vertebrates
VERTEBRATE ZOOLOGY (VZ Lecture03 – Spring 2012 Althoff - reference PJH Chapters 1,2 & 7) DIVERSITY, CLASSIFICATION & EVOLUTION PART III 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 ______________________ 1 _______________ “migrating” to branchial arches chicken embryo I – migrates to form mandible II—migrates to form hyoid apparatus III & IV—migrate to form outflow tract of heart 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 2 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 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 O2 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 O2 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 nonamniote 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) 3 4 2 1 5 Aquatic nonamniote tetrapods Fig. 7-5 p165 PJH Terrestrial nonamniote tetrapods