Lecture2 - Observations about Life Observations for...

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Observations for Evolution Bio 370 S.Hedtke September 1, 2009 Observations about Life • Life on earth is OLD • Diversity changes through time • Hierarchical structure of life on earth • Organisms fit their environment (adaptation) Any theory of life must be consistent with our observations. The Earth is Really, Really Old Our solar system was formed about 4.6 billion years ago, according to radiometric dating of meteorites and moon rocks. The Earth is the same age, but because of geological processes such as the subduction of crust, the oldest known rocks on earth date from only about 4.06 billion years ago. Life is OLD Oldest known fossils: stromatolites ~ 3.5bya Cyanobacteria/bacteria colonies The oldest fossils of multicellular animals are about 575 million years old. Life is OLD Stratigraphic record Photo: M. Elrick Life is OLD
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Trilobite ribs over 3-million year stratigraphic section Changes in “form” through time • Diversity Changes Through Time Stickleback morphology over 110,000 yrs Gradual and punctuated change! Changes in form through time Diversity Changes Through Time Burgess Shale fossils Diversity Changes Through Time We can’t know the full extent of how many species there used to be, how they’ve changed through time, or even how many there are now! • This is because: – The fossil record is incomplete – Current diversity is not completely surveyed – Current diversity is going extinct! Diversity Changes Through Time The Diversity of Life , E.O. Wilson ~ 5-10 million species, only 1.5 million named http://www.sp2000.org/ Extinction events frequent – at least five biggies Of the species that have existed, 99% extinct
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The distributions of some species makes no sense unless they have arisen from a common ancestor. Plate tectonics
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This note was uploaded on 10/03/2009 for the course BIO BIO taught by Professor Mueller during the Fall '09 term at University of Texas.

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Lecture2 - Observations about Life Observations for...

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