Bio1B Evolution 10 Last lecture The big 5 mass extinctions Species speciation Hybridization hybrid zones reinforcement hybrid speciation Macroevolution The fossil record extinctions and major transitions Today Fossil record cont Text Pp 521 524 Mass extinctions the Cretaceous Paleogene K T boundary cause consequence Transitional forms Terrestrial vertebrates tetrapods Birds evolution of feathers Evolution of development programs Text Pp 525 530 The eye vertebrate limbs 1 The asteroid impact hypothesis Luiz Walter Alvarez UC Berkeley Evidence from analyses of extinction red and blues diversity or families of marine invertebrates Permian Triassic 96 species extinction 8 27 orders of insects Volcanism in Siberia Cretaceous Paleogene K T 65 Myr demise of dinosaurs large terrestrial animals mammalian 2 radiation Understanding the transition of tetrapod vertebrates from water to land see Science 5th March p1214 Tiktaalik Fig 34 20 Acanthostega Faunal turnover Carbon cycle change Iridium spike 3 4 Modification of existing structures for new purposes ears and feathers Feathers for display or warmth before flight Late Jurassic feathered dinosaur Fig 34 31 Bones of inner ear of modern mammals are derived from jaw joint of ancestors see also Fig 25 6 Recent discovery dinosaur feathers were colored display Molecular homology genes with common ancestry controlling development top right Changes in timing and spatial pattern of expression change in phenotype E g Ubx suppresses leg development in flies but not shrimp 5 Fig 25 22 6 Origin of novelty The eye Origin of novelties The vertebrate limb Are the fish fin and vertebrate limb homologous Very different anatomy yet Similar patterns of Hox gene expression Anatomic differences could be due to modification of timing duration of expression Evolution of developmental genes phenotypic novelty Convergent evolution or descent with modification Shubin et al 2009 Nature 457 818 7 Molecular homology of key genes Pax 6 opsin pathway Subsequent modification of pathways and structures Both in annelids Shubin et al 2009 Nature 457 818 8
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