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1.A.4 Evidence of Evolution Biological evolution is supported by scientific evidence from many disciplines, including mathematics. Warm-Up 1. Compare and contrast natural selection vs. artificial selection. 2. What are the key ideas of natural selection? Warm-Up 2. Define and give an example for the following: • Homologous structure • Vestigial structure • Analogous structure Scientific evidence of biological evolution uses information from geographical, geological, physical, chemical and mathematical applications. Molecular, morphological and genetic information of existing and extinct organisms add to our understanding of evolution. Fossils show change over time. How rocks and fossils are dated Relative dating: dating a fossil relative to other fossils, without knowing its actual age. • Strata at one location correlated to strata at another location Dating fossils using the relationships within phylogenetic trees Absolute dating: Determining a Fossil’s Age in Years • Radiometric Dating • Mathematical Calculations Radiometric dating – dating using decay of radioactive isotopes • Radioisotopes have a half-life: the number of years it takes for 50% of the original sample to decay. • Incredibly reliable method for dating; only 1% error rate! How Radiometric Dating Works: Carbon-14 is a very important radioisotope • An organism accumulates some carbon-14 in its body when it is alive • When the organism dies, the carbon-14 will start decaying to become nitrogen-14 C-14 is used to date fossils up to 75,000 years old • For older fossils, radioisotopes with longer half-lives are necessary • Can also date the rocks that fossils are found in Mathematical calculations can take into account information from chemical properties and/or geographical data. Graph of Uptake of Trace Elements by Diffusion of a Fossil Magnetic reversals can be used to date rocks when other methods fail. ― Occur when the earth’s north and south magnetic poles reverse. Morphological homologies represent features shared by common ancestry. Homologous Structures: arisen from common ancestor. • Same structure, but different function Analogous Structures: no recent common ancestor; due to convergent evolution. • Same function, but different structure What do all of these organisms have in common? Vestigial structures are remnants of functional structures, which can be compared to fossils and provide evidence for evolution. Vestigial Structures in Humans: • Tailbone • Wisdom teeth • Vomeronasal organ (secondary sense of smell found in some animals) • Ear-orienting muscles • Goosebumps Biochemical and genetic similarities, in particular DNA nucleotide and protein sequences, provide evidence for evolution and ancestry. Example: Analysis of sequence data sets The universal genetic code: implies that all life on earth ultimately descends from a common ancestor. Mathematical models and simulations can also be used to illustrate and support evolutionary concepts: ex) Hardy-Weinberg Equilibrium. Example: Graphical analyses of allele frequencies in a population Biogeography: geographic distribution of species • Closely related species are usually found in the same geographic region Comparative embryology: embryos of vertebrates share many anatomical homologies