Lecture_25_DulaiS09_MacroEvolution

Lecture_25_DulaiS09_MacroEvolution - Evolutionary Patterns,...

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Evolutionary Patterns, Rates, and Trends
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Fossils • Recognizable evidence of ancient life – Fossilized hard parts (most common) – Trace fossils (indirect evidence)
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Fossils and the Great Deluge • Fossils of seashells have been found in rock layers high in the mountains • How did they get there? • Initial explanation was that they had been deposited during the biblical flood
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Evidence of Past Life • 1700s • Excavations unearthed similar fossil sequences in distant places • Scholars began to view these findings as evidence of the connection between Earth history and the history of life
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Fossilization • Organism becomes buried in ash or sediments • Rapid burial and a lack of oxygen aid in preservation • The organic remains become infused with metal and mineral ions
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Stratification • Fossils are found in sedimentary rock • This type of rock is formed in layers • In general, layers closest to the top were formed most recently
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What Do Fossils Tell Us? • As a result of mutations, natural selection, and drift, each species is a mosaic of ancestral and novel traits • All species that ever evolved are related to one another by way of descent MOVIE
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Radiometric Dating MOVIE after two half-lives after one half-lives parent isotope in newly formed rock
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Geologic Time Scale • Boundaries based on abrupt transitions in fossil record • Correspond to mass extinctions • Archean eon (oldest interval) • Proterozoic eon • Paleozoic era • Mesozoic era • Cenozoic era (most recent)
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Macroevolution The large-scale patterns, trends, and rates of change among families and other more inclusive groups of species
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Continental Drift • Idea that the continents were once joined and have since “drifted” apart • Initially based on the shapes • Pangea: theoretical supercontinent
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Evidence of Movement • Evidence cited from glacial deposits and fossils • Later was discovered that magnetic orientations in ancient rocks do not align with the magnetic poles • Discovery of seafloor spreading provided a possible mechanism
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Plate Tectonics • Earth’s crust is fractured into plates • Movement of plates is driven by upwelling of molten rock at mid-oceanic ridges • As seafloor spreads, older rock is forced down into trenches
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Forces of Change island arc oceanic crust oceanic ridge trench continental crust subducting plate athenosphere (plastic layer of mantle) hot spot lithosphere (solid layer of mantle)
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Gondwana • Supercontinent preceding Pangea • Same series of glacial deposits, coal seams, and basalt are found in Africa, India, Australia, and South America • Antarctica contains same fossils as other southern continents
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Changing Land Masses 10 mya 65 mya 260 mya 420 mya
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Comparative Morphology • Comparing body forms and structures of major lineages • Guiding principle: – When it comes to introducing change in morphology, evolution tends to follow the path of least resistance
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Morphological Divergence • Change from the body form of a common ancestor • Produces homologous structures that may serve different functions
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Lecture_25_DulaiS09_MacroEvolution - Evolutionary Patterns,...

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