Bio171-F08-lec26 - Lecture 26: Monday, November 3, 2008...

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Unformatted text preview: Lecture 26: Monday, November 3, 2008 Biology 171 Todays Topic: History of Life on Earth & Fossil Record Announcements This Week in Discussion: Bacterial Diversity - Your Gut Flora Text Reading Lec 26: 2 nd ed: Chapter 26 (561-578) 3 rd ed: Chapter 27 (548-564) Lec 27: 2 nd ed: Chapter 27 (582-604) 3 rd ed: Chapter 28 (566-590) Phylogenetics (concluded) Age of the Earth Pre-Cambrian Life Concordance of Evidence Cambrian Explosion Post-Cambrian Diversification Mass-Extinction events How Old Is the Earth? Meteorites formed 4.58 Ga (billions of years ago), and the Moon formed 4.51 Ga. Earth must be about the same age, but no direct radiometric dating is How Old Is the Earth? Meteorites formed 4.58 Ga (billions of years ago), and the Moon formed 4.51 Ga. Earth must be about the same age, but no direct radiometric dating is possible because Earth was initially. Events at plate boundaries. At some plate boundaries, such as oceanic ridge, the plates separate, and molten rock wells up in the gap. The rock solidifies and adds crust symmetrically to both plates, causing seafloor spreading. At subduction zones, where plates move toward each other, the more dense plate dives below the less dense one, forming a trench. Samples of the earth's oldest rocks are extremely rare because rock is constantly recycled or sinks to the hot mantle of the Earth. MYA Zircon crystals with ages >4000 Ma have been found in these rocks, including a 4,404 +/- 8 Myr zircon. The rocks themselves are younger (3800 Ma). The oldest dated material on Earth. Using the Fossil Record The fossil record is the only source of direct evidence about what prehistoric organisms looked like, where they lived, and when they existed....
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This note was uploaded on 01/30/2012 for the course BIO 171 taught by Professor Josephinekurdziel during the Fall '08 term at University of Michigan.

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Bio171-F08-lec26 - Lecture 26: Monday, November 3, 2008...

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