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Bio Midterm Study Guide October 3 2014 1 Chapter 23 Evolutionary Patterns a Reading a Phylogenetic Tree i Introduction 1 Phylogeny history of descent with branching 2 Node last common ancestors indicated by the point on the tree where they ii Phylogenetic trees provide hypothesis of evolutionary relationships branch off 1 Taxonomy a Def classification of organisms b Provides us with hierarchal classifications of species in more and more inclusive groups c Order 2 Phylogenetics domain i Species genus order class phylum kingdom a Aims to discover the pattern of evolutionary relatedness among groups of species or other groups by comparing their anatomical or molecular features and depict relationships as phylogenetic tree b Phylogenetic tree a hypothesis about the evolutionary history or phylogeny or a species group of organisms i The informal name at the end of each branch represents a iii The search for sister groups lies at the heart of phylogenetics ii Provides evolutionary information evolutionary relationships 1 2 species or a groups of species are closest relatives if they share a common ancestor not shared by any other species or group 2 Sister groups groups that are more closely related to each other than either of them is to any other group a A phylogenetic tree is simply a set of sister group relationships because the simplest phylogenetic questions is which 2 or any 3 species are more closely related to each other than the 3rd i Closeness of relationship is determined by looking at the tree and seeing how recently the two groups share a common ancestor 1 Shared ancestry is indicated by a node a Can be rotated without changing the evolutionary relationship Information about evolutionary relationship therefore lies in the order of nodes over time not in the order of groups along the tips iv A monophyletic group consists of common ancestor and all its descendants b 1 Taxon all species in a taxonomic entity such as family or genus 2 Monophyletic all members that share a single common ancestor not shared with any other species or group of species 3 Paraphyletic includes some but not all of the descendants of a common ancestor a If in order to separate the group from the rest of the phylogenetic tree you only have to make 1 cut monophyletic b If in order to separate the group from the rest of the phylogenetic tree you have to make 2 cuts paraphyletic 4 Polyphyletic groupings that don t include the last common ancestor of all members 5 Monophyletic groups are the main goal of phylogenetics because they include all descendants of a common ancestor and only the descendants of that common ancestor a Monophyletic groups alone show the evolutionary path of a given group has taken since its origin v Taxonomic classifications are information storage and retrieval systems 1 Genus closely related species are grouped into a genus a Genus family order class phylum kingdom domain b Building a Phylogenetic tree i Homology is similarity by common descent i The domains are Eukarya bacteria archaea 1 Characters the anatomical physiological or molecular features that make up organisms a Phylogenetic trees are inferred by comparison of character states shared among different groups of organisms b To be useful must vary among but not within species and have a genetic basis 2 All species contain some character states that are shared with other members of their groups some that are shared with members of other groups and some that are unique 3 Character states can be similar for 2 reasons a b It was present in the common ancestor of the two groups and retained over time common ancestry homology Independently evolved in the 2 groups as an adaptation to similar environments convergent evolution analogy ii Shared derived characters enable biologists to reconstruct evolutionary history 1 Homologies are useful in constructing phylogenetic trees because they are a result of common ancestry and analogies are not a Synapomorphies shared derived characteristics that are shared by some but not all members of the group i Cladistics phylogenetic reconstruction on the basis of synapomorphies iii The simplest tree is often favored among multiple possible trees 1 The least amount of changes 2 This is because they provide the simplest explanation for the data a Parsimony choosing the simpler of 2 hypothesis to account for a given set of observations i Each change corresponds to a mutation in an ancestral species and the more changes we propose the more independent mutations will also need to be hypothesized 3 Multiple diverging groups indicate that we lack the data to choose unequivocally among several different hypothesis of relationships iv Molecular data complement comparative morphology in reconstructing phylogenetic history 1 Tree reconstruction relies on molecular data also c The Fossil Record i Introduction a The amino acids at a particular position in the primary structure of a protein and the nucleotides at a specific positions on a strand of DNA can be used 2 Comparative morphology the study of structures and forms in different taxa 3 Different way of reconstruction distance rather than synapomorphies a Descendants of a recent common ancestor will have had relatively little time to evolve differences whereas the descendants of an ancient common ancestor have had a lot of time to evolve differences 1 Branches toward the base of the tree occurred earlier than those near the top and characters change and accumulate along the path from the root to the tips ii Fossils provide unique information 1 Fossils allow researchers to calibrate phylogenies in terms of time 2 They provide the only record or extinct species 3 They place evolutionary events in context of Earth s dynamic environmental history iii Fossils provide a selective record of past life 1 Fossils the remains of once living organisms provided through time in sedimentary rocks 2 Requires burial or else the remains are recycled by biological and physical processes so no fossil would be produced 3 Fossil record of marine life is more complete than in land dwelling creatures because marine habitats are more likely than those on land to be places where sediments accumulate and become rock 4 Biological factors contributing to fossil production a Mostly preserve the hard part of the organism b The environment 5 Trace fossils tracks and trails that burrow into sediments 6 Molecular fossils sometimes they leave behind molecular information lipids and


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UConn BIOL 1108 - Bio Midterm Study Guide

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