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Change Through Time
Evidence of change through time ` Central tenet of the Theory of Special Creation is that species, once created, are immutable. Microevolution fEvolutionary changes on the small scale, such as gene frequencies within a population Macroevolution fEvolution on the grand scale; events above the species. Change Through Time ` Direct observation of change of a species Soapberry bug evolved a shorter beak within 20 years of switching host plants 2 Change Through Time Evidence from living species ` Vestigial structures ` Can be identified at structural, developmental, and genetic levels ` Vestigial Organs ` A functionless or rudimentary version of a body part that has an important function in other, closely related species Vestigial Organs 3 Change Through Time ` Evidence from fossil record Fossils are unlike species living today Used to think that if we looked hard enough we would find those fossilized species alive somewhere Extinction eventually became known as a fact Special creationists asserted that extinct species were killed by biblical flood Change Through Time ` Evidence from fossil record Law of Succession shows extinct species are ancestors of living species f Did not die in flood leaving no descendants Pygmy Armadillo Fossil Glyptodont 4 Irish Elk (Cuvier) Change Through time Transitional forms fDarwin was concerned that no transitional forms had been found the first Archaeopteryx was found fIn 1860 Environmental change fMarine organism fossils found in deep deserts and on high mountains Transitional forms ` A. Archaeopteryx (140(140-150) ` B. Sinosauropteryx ` C. Dromaeosaurid Confusciousornis (modern(modern-looking bird) Primitive feathers Primitive feathers ` D. Modern feathers 5 Tree Thinking ` ` ` Species not independently created Darwin invented technique to illustrate how species are related by descent with modification Species form the Tree of Life 6 Relatedness of Life Forms ` Comte de Buffon, Buffon, Erasmus Darwin, JeanJeanBaptiste Lamarck had already proposed evolution by compiling evidence Homology fSimilarity due fComparative to common ancestry anatomy and comparative embryology fStructural, developmental, genetic 7 Genetic code Pseudogenes Functional genes = exons, exons, introns, introns, promoters ` Processed Pseudogenes =non=non-functional ` Arise from reverse transcription of mRNA ` Resulting DNA is inserted at another locus Newly created gene lacks introns, introns, promoter Pseudogenes 8 Relatedness of Life Forms Homology must be caused by relatedness ` Why else would the exact same underlying structures exist in very different organisms that have different ecologies? ` Evidence that all species are derived from each other ` Relatedness of Life Forms ` Galápagos Islands Darwin visited on HMS Beagle Impressed by similar but distinct species on each of the islands Mockingbirds Then, finches and tortoises A population must have arrived from South America on one island and spread to others fSpecies diverged separately on each island 9 Age of the Earth ` ` By the time of Darwin’s work, evidence was mounting that the earth is ancient Principle of Uniformitarianism James Hutton and Charles Lyell Same processes we see today have always been acting f Volcanoes, erosion, earthquakes, etc. Opposed principle of catastrophism f Geology result of catastrophic events The biblical flood Age of the Earth ` Geologists measured rockrock-forming processes and erosion rates Earth is unimaginably old Used relative dating ` Constructed geological time scale ` ` Assume that deepest rock layers are oldest http://www.enchantedlearning.com/subjects/Geologi http://www.enchantedlearning.com/subjects/Geologi ctime.html Each division is associated with a distinct fossil biota ` Absolute dates later added ` 10 Radiometric Dating ` ` Absolute dating of rocks Unstable isotopes decay at a constant rate Rate not affected by temperature or moisture ` Know halfhalf-life of isotope and measure amount of original and daughter isotope in rock sample Gives age of rock Radiometric Dating Radiometric Dating Different isotopes have appropriate halfhalflives for dating different time scales ` Some can be used to date the earth ` Because earth was molten at beginning, measure age of meteorites or moon rocks fBecause solar system started at same time Earth is 4.6 billion years old Life is 3.7 billion years old fFirst fossil life 11 Correspondence Among Data Sets ` Data in this chapter contradict three propositions of special creation Species created independently Species are immutable Earth is young ` If several data sets agree, we have even stronger evidence 12 Correspondence Among Data Sets Theory of Plate Tectonics ` Radiometric dating ` Magnetic field of earth ` Magnetic field frozen in rocks when they reach the crust so we know the direction of magnetic field at that time ` Combined with the fossil record, we have multiple lines of evidence Correspondence Among Data Sets ` History of marsupials Once lived only in North America Spread to Central and South America Spread to Antarctica, Europe, Africa, and Australia Spread to Asia Now only occur in the Americas and, especially, Australia Australia lacks placental mammals 13 Conclusions ` Darwin and others found evidence against Special Creation ` ` Homology Vestigial structures Direct observation Fossil record Geology Correspondence among data sets Created phylogenetic trees using parsimony Defeated special creation with evolution 14
