Dating Fossils

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Dating Fossils. http://www.uwo.ca/biology/images/undergraduate/trilobite.jpg. How old are fossils?. Oldest fossils 3.5 byo prokaryotes 1 st life forms are probably older What is evolution? The scientific theory that explains how species change over time - PowerPoint PPT Presentation

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  • http://www.uwo.ca/biology/images/undergraduate/trilobite.jpg

  • Oldest fossils 3.5 byo prokaryotes1st life forms are probably older

    What is evolution? The scientific theory that explains how species change over timeToday, species have changed both structurally & physiologically from what they were.

  • Remains/traces of once living organisms that no longer exist.Usually found in sedimentary rock the formation process is quick, preventing bacteria from decaying the organism.Usually consists of hard parts of the organism.Minerals may replace remains, preserving microscopic structures.

  • Freezing i.e. MammothsImprints film of carbon left after decayCasts sediments fill mold of organismKinds of fossils =- Whole organisms, bones, plants; feathers; pollen grains

    http://images.google.com/imgres?imgurl=http://notexactlyrocketscience.files.wordpress.com/2007/01/800px-microraptor_fossil1.jpg&imgrefurl=http

  • Relative age position in layers of sedimentary rocks.Absolute age radioisotopes w/unstable nucleii & a constant (known) rate of decayHalf-life length of time it takes of radioactive material to decay

    http://razd.evcforum.net/Pictures/CvE/carbon14decay.jpg

  • Atom with a different # of neutrons12C and 13C= 6P, 6N (7N) and are stable14C = 6P & 8N, unstable, life = 5730 yrsHow does dating work?1) ratio of 14C production/decay in atmosphere is constant2) organisms take in 12C & 14C at a constant rate

  • 3) organism dies 12C & 14C in atmosphere remain constant14C in organism decays12C : 14C ratio in organism changes4) compare 12C : 14C ratio in organism to atmospheric ratio5) scientists can date organisms up to 50K years using carbon dating.

  • Use different isotopes i.e. 40K (potassium 40), life = 1.28 billion yearsSo.How is all of this information applied to fossils we find in the dirt?http://images.usatoday.com/tech/_photos/2006/11/07/fossil472.jpg

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