Bio171-F10-Lec 26 - Biology 171 Friday, November 12, 2010...

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Unformatted text preview: Biology 171 Friday, November 12, 2010 Lecture 26: History of Life on Earth & Fossil Record Announcements Text Reading Lecture 26 : 4 th : Chapter 27 (479-492) 3 rd : Chapter 27 (548-564) Lecture 27 : 4 th : Chapter 27 (496-516) 3 rd : Chapter 27 (566-590) Phylogenetics (concluded) Age of the Earth Pre-Cambrian Life Concordance of Evidence Cambrian Explosion Post-Cambrian Diversification Mass-Extinction events 1 Next week in Discussion: Reconstructing Phylogeny Exam 3 Wed. Nov. 17 8-10PM Exam covers lectures 20-27 Discussions 6-8: (Genetics Problems, Evolution/Pop. Genetics, Sexual selection/speciation) Step 4 Use the relative numbers of synapomorphies to infer branching pattern 22 Using the parsimony principle , the frst cladogram is preFerred because it provides the simplest explanation For the observed pattern. Step 4 Use the relative numbers of synapomorphies to infer branching pattern 22 Using the parsimony principle , the frst cladogram is preFerred because it provides the simplest explanation For the observed pattern. ig. 27.4 How might we construct an inferred phylogenetic tree for all life on the Planet? In other words, how do we go from Darwins sketch to a meaningful tree of life? Identify a homologous character set found in all life forms that also shows variation that can be separated into plesiomorphic and apomorphic changes to yield synapomorphies throughout the tree. 23 Proteins carry out cellular functions. 24 Ribosomes are the universal ribonucleoprotein particles that translate the genetic code into proteins. Typical bacterial ribosomes consist of 57 different molecules ( 3 rRNAs and 54 proteins) and can dissociate into a small and a large subunit. Each subunit has a structural RNA backbone that is homologous among all life forms that can be sequenced, aligned and analyzed for plesiomorphic and synapomorphic states. Model of Bacterial Ribosome subunits 25 (Unrooted no outgroup) Tree of Life based on Ribosomal RNA sequences. 3 Domains Root is the hypothetical position of the common ancestor of all life forms What minimal attributes must it have possessed?...
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Bio171-F10-Lec 26 - Biology 171 Friday, November 12, 2010...

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