Bio171-F08-lec29 - Lecture 29: Monday November 10, 2008...

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Unformatted text preview: Lecture 29: Monday November 10, 2008 Biology 171 Todays Topic: Origins of Eukaryotes; Diversity of Protists Announcements This Week in Discussion: Pandemic Influenza Exam III, Monday, November 17 Covers Lectures 20-29 Review Sunday Nov. 16th 4-6pm Room: TBA Endosymbiotic Origins of Eukaryotes Protist Diversity - New Molecular Perspectives Photosynthesis & 2ndary Endosymbioses Malaria Trypanosomes Text Reading Lec 29: 2 nd ed: Chapter 28 (607-634) 3 rd ed: Chapter 29 (593-623) Lec 30: 2 nd ed: Chapters 31-33 (Sponges; Protostomes; Deuterostomes) 3 rd ed: Chapters 32-34 Animal Eukaryotic Cell Prokaryotic Cell. Eukaryotic Cells represent a quantum leap in size and complexity. How did they evolve? Prof. Lynn Margulis (University of Massachusetts, Amherst) In 1967, she proposed an endosymbiotic hypothesis for the origin of mitochondria : these organelles evolved from free-living bacteria that long ago entered into a symbiosis with ancestral eukaryotes . Similar proposals had previously been made for chloroplasts . She was criticized as a radical, and her scientific work was rejected by mainstream biology for many years. Her work has more recently received widespread support and acclaim. Her hypothesis that the eukaryotic cell is a symbiotic union of primitive prokaryotic cells has been hailed as one of the great achievements of twentieth-century evolutionary biology Richard Dawkins A model of the origin of eukaryotes through serial endosymbiosis. Evolution of Eukarya Mitochondria and chloroplasts are about the size of an average bacterium. Both organelles replicate by Fssion, as do bacteria, and have their own ribosomes to manufacture their own proteins. Both organelles have double membranes, consistent with the engulFng mechanism. Mitochondria and chloroplasts have genes that code for the enzymes needed to replicate and transcribe their own genomes. Do the Data Support the Endosymbiosis Theory? These lines of evidence are highly suggestive, but not conclusive. Margulis predicted that organelles of endosymbiotic origin would have their own DNA that would differ from the DNA of the rest of the cell - she was proven to be correct in the case of mitochondria and chloroplasts ....
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Bio171-F08-lec29 - Lecture 29: Monday November 10, 2008...

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