08-29 - BIO 5099 Molecular Biology for Computer...

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BIO 5099: Molecular Biology for Computer Scientists (et al) Lecture 4: Some eras and their creatures http://compbio.uchsc.edu/hunter/bio5099 [email protected] Housekeeping Problem set answers and discussion (Raphi and Christiaan) Center for Computational Biology Certificate program. Mass Extinction Events Several times in the history of life, large proportions of the species present in the fossil record disappear forever. These are crucially important in the history of life (remember the effects of bottlenecks on allele frequencies) Marine genus-level extinctions
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Causes of mass extinctions Two classes seem to have happened Terrestrial agents Volcanoes Climate change Environmental change Extraterrestrial agents Meteorite impacts Cosmic rays? Periodicity?: Various cycles in extinction data, including with 26M and 60M year periods. Effects of Mass Extinctions Marine and terrestrial species tend to both be effected (since origin of terrestrials). Impact tends to be worse on marine organisms. On the land, plants tend to be more resistant to extinctions than animals Preferential disappearance of tropical forms Some organisms survived more than one Trilobites and ammonoids Hard to quantify microorganism effects Precambrian Extinctions About 2.2Ga (halfway to the origin) the first pollution catastrophe struck: Oxygen. Oxygen is a toxic (to them) waste product of many bacteria. Early atmosphere was less than 1% oxygen. May be related to the origin of Eukaryotes About 650Ma a huge glaciation wiped out about 70% the existing species. At the end of the precambrian, another large extinction wiped out organisms similar to jellyfish, sea pens and segmented worms.
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Permian Extinction The Permian extinction ended the Paleozoic era, about 250Ma. Worst in history. 85% of marine species and 70% of terrestrial species went extinct. Cause was likely volcanism. Eruption at just that time in Siberia covered 4M sq. kilometers in lava (twice the size of Europe). Not just lava, but huge volumes of soot, sulfur dioxide, greenhouse gases, etc. K-T extinction The mesozoic era was ended by the Cretaceous/Tertiary extinction, which killed the dinosaurs. Second largest extinction, eliminating about 80% of all species. Likely cause was a meteor impact, although also significant volcanism at the time Iridium layer at the boundary Large impact site with good timing in Yucatan, Mexico Large eruptions at same time (India/Pakistan border) Anthropogenic mass extinction Broad consensus among biologists, but still some holdouts. UN Environment Program report in May '02:
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This note was uploaded on 09/20/2011 for the course CSC BIO 5099 taught by Professor Prof.larryhunter during the Fall '02 term at University of Colorado Denver.

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08-29 - BIO 5099 Molecular Biology for Computer...

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