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Evidence of Evolution View this in presentation mode and listen to the audio! Dating Rocks • Relative dating: using the position of the rocks in the rock layer to determine which are older (superposition) • Absolute dating: Using the decay of isotopes to determine a more precise age of rocks (radiometric dating) Radiometric dating • Radiometric dating: is a measure of the decay of isotopes •Isotopes decay at a known rate called Half-life. •Half-life is the amount of time need for ½ of a sample of radioactive material to decay •The age of a rock can be calculated using the formula: •time = duration of half-life X # of half-lives that have occurred. Calculating rate of decay • Each isotope has a known half-life. – For example the half-life of Iodine-131 is 8.1 days. • The number of half-lives passed can be calculated by knowing what fraction of the parent isotope is remaining. – ½ remaining = 1 half life, ¼ = 2, 1/8 = 3 etc. test yourself: If there is ¼ of iodine-131 remaining how much time has passed? 2 x 8.1days = 16.2 days Types of evidence • • • • Fossil record Transitional species Homologous structures Vestigial structures •Biological molecules: DNA, RNA, proteins •Embryology •Antibiotic resistant bacteria Fossil record & transition species • Transitional fossils • Darwin predicted they would be found. • Links today’s forms with ancestral form. • Birds/reptiles • Land/sea mammals • Four legged animals with fish. what do you think this fossil is a link to? Homologous Structures • Different shape and function today. • Same evolutionary origin. – Ex: Bones of the forearm of mammals. Vestigial Structures • Structure is coded for in the DNA. • Function has apparently been lost. – Ex: Human appendix? Similar macromolecules – Related species have the same or very similar DNA and proteins. – Distantly related organisms have dissimilar DNA and proteins. – Vital genes and proteins change little over time. (conservative traits) – Universality of genetic code What more closely related a pigeon and a monkey or a pigeon and a bull frog? Similarity in Embryology • Embryos of similar species look the same. • Embryos of related species go through the same steps. Antibiotic resistant bacteria • Evolution is continuous • Bacteria that are resistant to antibiotics will survive when those that are not won’t – Thereby passing on antibiotic resistant genes In your summary answer these questions, pick one cartoon to explain, and explain how antibiotics relate to evolution. 1. What is an homologous structure? 2. How are embryos evidence of evolution? 3. Name a way to show species are closely related.