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Illustrating Evolutionary Relationships Between Organisms



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Biology 18 Spring 2008 Lab 2 Illustrating Evolutionary Relationships Between Organisms Emperor Penguins and Phylogenetic Trees Pre Lab Reference Reading Review pp 542 556 and pp 722 737 in Life by Sadava et al 8th edition 2006 I Introduction The ability to think broadly about the living world is rooted in an understanding of life s diversity However the large number of ways in which various organisms differ from one another can often mask their similarities The diversity and unity of living organisms would seem to be contradictory concepts Recall though that these were the major themes in Darwin s great work in which he asked and answered the following question Since life is so diverse are there any unifying themes at all By looking backwards in time Darwin showed that the answer to this question is a resounding Yes Time Darwin proposed both a pattern invoking common descent as the basis for the unity of life and a mechanism to explain how the relationships between species became fragmented over time resulting in diversity In addition Darwin himself is responsible for the metaphor that is used today to illustrate this shared descent of living organisms the Tree of Life TOL In fact the diagram shown below was the only figure from his book On the Origin of Species by Natural Selection great tree of life with its ever branching and beautiful ramifications C Darwin 1859 The ATOL Assembling the Tree of Life Project represents a collective effort of biologists working on different organisms to understand how the diversity of life fits together Resolving evolutionary relationships that underlie the TOL is unquestionably one of the most important problems in biology today for two major reasons Because it is relevant to all organisms with the tree potentially encompassing the 1 75 million living species characterized to date and an estimated tens of millions more to be discovered not to mention the even larger number of species that existed and are now extinct There are



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