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LONG-TERM EVOLUTIONARY EXPERIMENTS CHAPTER 6 http://natsci.edgewood.edu/wingra/Student%20Projects%2 02008/E.%20Coli/default.htm ADAPTIVE RADIATION STUDIES PROVIDE LIMITED INFORMATION AS TO WHY IT HAPPENED AND WHAT OTHER POSSIBILITIES MAY HAVE BEEN POSSIBLE. http://news.nationalgeographic.com/news/bigphotos/83795719.html CLASSICAL STUDIES: GALAPAGOS FINCHES, AFRICAN CICHLIDS, STICKLEBACKS THE THEORY OF EVOLUTION BY NATURAL SELECTION PROVIDES A CAUSE-AND-EFFECT FRAMEWORK (EVEN MATHEMATICALLY) BUT NOT THE MECHANISMS. SHORT-TERM SELECTION VERSUS • Long-term studies are LONG-TERM STUDIES SHORT-TERM • limited number of generations • Can lead to erroneous inferences regarding genetic correlations LONG-TERM • Association of organism and environment is open-ended • Direct investigation of why an adaptation happened (causality) • Model organisms - insects (Drosophila) or microbes (E. coli) able to study the importance of chance impacts on adaptation www.nature.com http-//louisproyect.wordpress.com CLONAL INTERFERENCE MAINTAINS DIVERSITY Periodic selection : natural selection recurrently purges diversity within a bacterial population Recombination in bacteria is rare Diversity is generally transient Larger populations (possible via long-term studies) >> multiple beneficial mutations>> diversity persists 3 ways ( Dr. Bennett) http-//www.nature.com/nrg/journal/v4/n6/box/nrg1088_BX2 ADAPTIVE RADIATION: Trade-off between resource breadth and competitive ability • Organism may be good at using one resource and not another>>>leads to co-existence of species http://natsci.edgewood.edu/wingra/Student%20Projects%202008/E.%20Coli/default.htm SUMMARY Long-term studies • direct observation of adaptation • mechanisms of adaptation • evaluation of environmental and genetic factors • causality of evolutionary change References • • • • • • http://abcnews.go.com/Technology/DyeHard/climate-change-find-tiny-sticklebackfish-evolved-temperatures/story?id=11368797 http://www.plosbiology.org/ http://www.biomedcentral.com/1471-2148/10/11 http://beaker.biology.washington.edu/research/pubs/2002/Bohannan_et_al2002.pdf http://www.hhmi.org/genesweshare/e120.html http://www.nature.com • http://www.nanobugs.com/ • • http://www.ncbi.nlm.nih.gov http://news.nationalgeographic.com/news/bigphotos/83795719.html http://www.plosbiology.org/article/info:doi%2F10.1371%2Fjournal.pbio.1000250