Bio 1202 Exam 2 Notes - Bio 1202 Exam 2 Notes Chapter 26...

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Bio 1202 Exam 2 Notes 03/09/2012 ° Chapter 26 Phylogeny and the Tree of Life ° ° Phylogeny – the evolutionary history of a species or group of species ° Systematics – a discipline focused on classifying organisms and determining their evolutionary relationships ° - use data ranging from fossils to molecules and genes to infer evolutionary relationships ° - an organism is likely to share many of its genes, metabolic pathways, and structural proteins with its close relatives ° Taxonomy – the scientific discipline of how organisms are named and classified ° Binomial – the two-part format of the scientific name, instituted by Carrolus Linnaeus ° Genus – first part of a binomial ° Specific epithet – second part of the binomial, which is unique for each species within the genus ° Taxon – the named taxonomic unit at any level of the hierarchy ° Phylogenetic tree – branching diagram that represents the evolutionary history of a group of organisms ° - represents a hypothesis about evolutionary relationships ° PhyloCode – only names groups that include a common ancestry and all of its descendants ° - would change the way taxa are defined and recognized, but the taxonomic names of most species would stay the same ° - species would no longer have “ranks” attached to them, such as family, order, or class ° - commonly recognized groups would become part of other groups previously of the same rank ° Branch points – represents the divergence of two evolutionary lineages from a common ancestor ° Sister taxa – group of organisms that share an immediate common ancestor and are each other’s closest relatives ° Rooted – a branch point within the tree represents the last common ancestor of all taxa in the tree
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° Polytomy – a branch point from which more than two descendant groups emerge ° - sequencing of branching in a tree does not necessarily indicate the actual ages of the particular species ° - cannot assume that a taxon on a phylogenetic tree evolved from the taxon next to it ° Homologies – similarities due to shared ancestry ° Analogy – similarity due to convergent evolution, rather than to shared ancestry (homology) ° - ex: bats vs. birds – seem similar but closer examination reveals that a bat’s wing is far more similar to the forelimbs of cats and other mammals than to a bird’s wing – therefore it is analogous to a bird’s wing ° Homoplasies – analogous structures that arose independently ° - the more points of resemblance that two complex structures have, the more likely it is that they evolved from a common ancestor ° - if genes in two organisms share many portions of their nucleotide sequences, it is highly likely that the genes are homologous ° - if the species are very closely related, the sequences probably differ at only one or a few sites; in contrast, distantly related species usually have different bases at many sites and may have different lengths – this is
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