chapter21.5 - Dakotah Forell Chapter 21 9-13-10 Evidence...

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Chapter 21 9-13-10 Evidence from the fossil record -If the theory of evolution is valid, then there is a temporal relationship between the appearance of fossil remains and age of geological formations. Radioactive Decay -Determining the age of sediments and fossils -Radioactivity = isotopes 12 C 14 C 14 C 14 N -Radioactive dating: half-life = time for ½ atoms to disintegrate -Half-life for 238U to 206Pb is 4.5 billion years (b.y.) Radio Active Elements Common dating methodologies ½ LIFE U Pb direct decay 4.5 b.y. (AGE OF EARTH) K Ar direct decay 1.25 b.y. Ru Sr direct decay 48.8 b.y. 14 C 12 C C to N decay 5,730 y Reliability of dating methods 1. Test for constant decay 2. Test against samples of unknown ages 3. Cross-checking methods ( most powerful technique in science) 4. Compare dates and strata levels Why do imperfections exist in the fossil record? 1. Most organism don’t fossilize -- soft tissues and stable environment 2.
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This note was uploaded on 07/26/2011 for the course BIO 200 taught by Professor Herreid during the Fall '07 term at SUNY Buffalo.

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chapter21.5 - Dakotah Forell Chapter 21 9-13-10 Evidence...

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