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Evidence of Evolution • Anatomical Structures: – Homologous & Analogous Structures • Embryology & Molecular Similarities: – Early Development • Biogeography: – Geographic Distribution of Living Things • Fossil Record • Phylogeny ANATOMICAL STRUCTURES: Homologous structure: Similar structure and position, but different function Courtesy of Prof. Ken Sytsma http://evolution.berkeley.edu Analogous structure: Similar function, but different origin ANATOMICAL STRUCTURES: Evidence for Evolution • Vestigial Structures – structures that serve no useful function in an organism • Examples: appendix, miniature legs, arms Embryology is the study of organisms in embryonic stages. The embryo is one of the earliest stages of growth and development of both plants and animals. The shared features in the embryos suggests evolution from a distant common ancestor. MOLECULAR: BIOCHEMISTRY All living things have A,T,C,G in their DNA and use the same codon chart to code for the same amino acids. Biogeography “ the study of what organisms live where on earth and why” (from Humphries and Parenti, 1999) • For fossils to form, organisms usually have to be buried in mud, sand, or clay soon after they die. • Most fossils are found in sedimentary rocks. rocks form atfound relatively temperatures and pressures • These Fossils are not usually in otherlow types of rock because of the ways thosemay rocksprevent form. that damage to the organism. • Fossils are evidence of organisms that lived long ago that are preserved in Earth’s rocks. TYPES OF FOSSILS Fossils Types Formation A trace fossil is any indirect evidence Trace fossils Casts left by an animal and may include a footprint, a trail, or a burrow. When minerals in rocks fill a space left by a decayed organism, they make a replica, or cast, of the organism. A mold forms when an organism is Molds Petrified fossils Amber-Preserved or frozen fossils buried in sediment and then decays, leaving an empty space. Petrified-minerals sometimes penetrate and replace the hard parts of an organism At times, an entire organism was quickly trapped in ice or tree sap that hardened into amber. • Relative dating • LAW OF SUPERPOSITION: • This method basically indicates that the fossils found closer to the surface are younger and more complex, and the fossils found in deeper strata are more primitive (older). • Relatively simple & less time consuming Compared to other methods • This method does not give a specific age of the fossil or rock. • To find the specific ages of rocks, scientists use absolute dating, also called Radiometric Dating or Carbon Dating. • In this type of dating scientists use radioactive isotopes to determine the absolute age of objects. As specific atoms decay they emit radiation and lose electrons, which causes them to turn into a different element. So- these atoms change from one thing into something else over time- and they do this at a constant rate. • The half-life of a radioactive atom is the time it takes for half of that atom in a sample to decay and turn into another element. Warm Up • If the decay rate of Carbon-14 is 5730 years: – How many years and half-lives will it take a organism to have less than 1% of Carbon-14 remaining? Warm Up • If the decay rate of Carbon-14 is 5730 years: – How many years and half-lives will it take a organism to have less than 1% of Carbon-14 remaining? – (7 half-lives) X 5730 years/half-life = 40,110 Years – 7 half-lives: 100%/2= 50%/2= 25%/2= 12.5%/2= 6.25%/2= 3.125%/2= 1.6%/2= .78% – How many years and half-lives will it take that same organism to be a little over 6% remaining? Overview: Investigating the Tree of Life • Phylogeny is the evolutionary history of a species or group of related species • The discipline of systematics classifies organisms and determines their evolutionary relationships • Systematists use fossil, molecular, and genetic data to infer evolutionary relationships Constructing a CLADOGRAM: What is Phylogenetics? Phylogenetics is the study of evolutionary relationships Example - relationship among species primates rodents birds crocodiles marsupials lizards snakes crocodiles birds lizards snakes rodents primates marsupials What is Phylogenetics? Phylogenetics is the study of evolutionary relationships Example - relationship among species primates rodents birds crocodiles marsupials lizards snakes crocodiles birds lizards snakes rodents primates marsupials