Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22EVOLUTION OVERVIEWIn talking about the fossil past, we need tounderstand that the world did not alwayslook the way it does nowIn particular, the continents used to be in different locations, with different climates and vegetationThe significance for us is that the environment was changingA changing environment means there wasnatural selection, resulting in variationVocabulary:bya = billion years agomya =million years agoya = years ago Scientific notation:Genus is always capitalizedSpecific epithet is never capitalizedBoth are italicized when typed/printed;when handwritten, they are underlinedGenus may be abbreviated when understood.Homo sapiens H. sapiensEstimate age of universe about 15 billion yearsFormation of earth about 4.5 byaFirst life on earth 3.6 bya – organic moleculesBy 2.4 bya, oxygen in atmosphereAround 1 bya, the beginning of sexual reproduction530 mya first vertebrates425 mya fish, complex land plants, land animals235 mya dinosaurs220 mya true mammalsTheory of Plate Tectonics:the Earth’s outermost layer is fragmented into a dozen or more plates that move We call this movement continental drift(http://www.ucmp.berkeley.edu/geology/tecmech.html; Feb. 22, 2005)The main features of plate tectonics are: •The Earth's surface is covered by a series of crustal plates. •The ocean floors are continually, moving, spreading from the center, sinking at the edges, and being regenerated. •Convection currents beneath the plates move the crustal plates in different directions. •The source of heat driving the convection currents is radioactivity deep in the Earth’s mantle.(http://www.ucmp.berkeley.edu/geology/tecmech.html; Feb. 22, 2005)TYPES OF PLATE MOVEMENT: Convergence, Divergence, and Lateral Slipping(http://www.enchantedlearning.com/subjects/astronomy/planets/earth/Continents.shtml;22 Feb. 2005)(http://www.ucmp.berkeley.edu/geology/tecmech.html; Feb. 22, 2005)New oceanic crust formsalong a mid-ocean ridgeSubduction occurs where aheavier oceanic plate meetsand goes under a continental plateWhere two oceanic plates meet, volcanoes may formWhere two plates collide and move laterally(sideways) to each other: earthquakesWhere two continental plates meet, mountains may form(http://www.enchantedlearning.com/subjects/astronomy/planets/earth/Continents.shtml;22 Feb. 2005)The original large landmass was Pangaea,which existed during the Permian throughJurassic periods, 235 - ca. 200 mya(http://pubs.usgs.gov/publications/text/historical.html#anchor4833509;21 Feb 2005)At the time of Pangaea (235-200 mya):The earth was tropicalThe first “primitive” dinosaurs appearThe very first mammals appearThese earliest mammals weretiny and probably nocturnalSo, in thinking about spread of mammals,the earliest mammals were present whenthere was just one large landmassBy the end of the Triassic/beginning of theJurassic (200 mya), Pangaea was splitting into twolarge landmasses, Laurasia and GondwanalandLaurasia: North America, EurasiaGondwanaland: South America, Africa, Australia, Antarctica, and India(http://pubs.usgs.gov/publications/text/historical.html#anchor4833509; 21 Feb 2005)At about 200 mya, when Pangaea was splitting into Laurasia and Gondwanaland(end of the Triassic & beginning of the Jurassic period):The Triassic period ended with a mass extinction accompanied by huge volcanic eruptions about 208-213 mya Most of the early, primitive dinosaurs went extinct, but other, more adaptive dinosaurs evolved in the Jurassic. Possible causes for this late Triassic extinction: global cooling or an asteroid impact.This extinction allowed the newer dinosaurs to expand into many niches that were now unoccupied. Dinosaurs would become increasingly dominant, abundant and diverse, and remained that way for the next 150 million years. Early mammals were roaming the forest floors and the first birds (150 mya) had also appeared.About 140 mya, the first floweringplants appear (beginning of Cretaceous period)These are to become important food sourcesfor mammals and early primatesThe Cretaceous period, 146-65 mya, was the heyday of dinosaurs. Mammals and flowering plants were developingThe Cretaceous ended 65 mya with massiveworld-wide extinctions, including the extinctionof dinosaurs except for birds (asteroid impact?!)This marks the end of the Mesozoic Era,The beginning of the Cenozoic Era, andbeginning of the Tertiary period,one period of main interest to us in this class(Kottak 2004:146)Pangaea is tropical;dinosaurs; 1st mammalsSplitting: Laurasia/Gondw.Mass extinctionsDinosaurs! 1st flowering plantsAsteroid: extinctions!end of dinosaursOur main periodsof interestSUMMARY prior to 65 myaContinents have moved, climate has changedTheory of Plate Tectonics explains how continents have moved: continental driftWhile Pangaea was the only landmass,and when Laurasia and Gondwanaland pullingapart, prior to 65 mya, there were a lot ofdinosaursMammals were small, nocturnalFlowering plants developed: food source for mammalsHuge change at 65 mya -- asteroid hit earth!All dinosaurs (except birds) went extinctEnd of Cretaceous, beginning of Tertiary period(end of Mesozoic, beginning of Cenozoic Era) 65 myaAt that time, North America was connected toEurasia, but not to South AmericaMost landmasses were tropical or subtropicalNow that dinosaurs are extinct, there is amajor mammal radiationERA Period Epoch65 mya55 mya36 mya24 mya1.7 mya(http://www.ucmp.berkeley.edu/cenozoic/cenozoic.html;22 Feb 2005)5 myaGeologic Time ScaleTo summarize the Era of most interest to us:Within the Cenozoic Era, Tertiary Period (65 mya - 1.7 mya)Quaternary Period (1.7 mya – now)Within the Tertiary Period, from oldest tomost recent, the geological epochs are:Paleocene, Eocene, Oligocene, Miocene, Pliocene(remember PEOMP)Within the Quaternary Period, from oldest tomost recent, the geological epochs are:Pleistocene (1.8 mya - 10,000 ya), Holocene (10,000 ya -
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