Bio 3400 1nd Edition Lecture 16 Outline of Last Lecture I Waterslider selection II Detecting selection at the molecular level III Types of Mutations IV Three spined sticklebacks Outline of Current Lecture I Phylogenetic Trees II Monophyly versus Paraphyly III Homology vs Homoplasy IV Molecular Clocks Current Lecture Statistical Methods Linnean Taxonomy vs Phylogenetic Taxonomy Charles Linneaus phylogenetic trees I Linnean rigid hierarchy kingdom phylum etc a Sub groups for those that don t fit b No room for fossils c Required expert knowledge of groups II Phylogenetic a Phylogeny the course of evolution Basic Premise of Phylogenetics I All life can be grouped into a nested hierarchy by homologous characters a DNA structure is identical b Metabolism basically works the same in all animals c Nucleus organelles chromosomes II Most parsimonious simplest explanation to conclude that there were inherited from a common ancestor III The most closely related taxa should have the most traits in common Tree Terminology I Node points where one species split into two or more descendent species II Root common ancestor of all species on tree III Tips most recent species usually extant IV Sister taxon the hypothesized closest genealogical relative of a taxon exclusive of their most recent common ancestor These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute V Taxon taxa a grouping given a proper name Monophyly vs Paraphyly I Monophyletic group natural clade a Single common ancestor b All of it s known descendants II Paraphyletic group a Single common ancestor b Does not include all descendants c Non avian dinosaurs Homology I Any similarity between species that is due to inheritance from a common ancestor Homoplasy II Similar character states that evolved independently III Examples loss of limbs fish whales snakes lizards streamlined morphology in sharks and dolphins etc All life can be grouped into a nested hierarchy by homologous characters I Types of Data Charcters Traits a Anatomy b Development c DNA RNA mtDNA etc d Behavior e Physiology II Making Trees a Use data to arrange organism by their ordered branching of evolutionary relationships b Goal identification ofmonophyletic groups natural groups or clades c Taxa mammalia canis familiaris are defined by characters d Parsimony i Fewest number of changes ii Maximum parsimony for many characters iii Lowest sum total number of changes e Objective not subjective i Not based on individual bias ii Assumes no a priori hypotheses of relationships III What defines monophyletic groups clades a Synapomorphies Shared derived characters i Ex 5 fingers fur feathers in birds must be unique to group b Must have the same character state c Must be homologous the same characters IV Character Polarity and Outgroups V a Character state any trait value for a taxon b Polarity primitive vs derived directionality of how a character evolved i Jawless primitive jawed derived c Outgroup a more primitive group included to allow character polarity to be assessed all primitive The Molecular Clock a How do we know when things happened i Geological timescale radiometric dating is used to date fossils ii Can we use molecular data to estimate the date of events not documented in fossils b Expected Patterns of Molecular Evolution from i Genetic drift constant rate of substitution that is equal to the mutation rate ii Use molecular traits that change at a steady rate timing and rate of evolution iii Date the common ancestor between two groups iv Date major evolutionary events v Especially useful when the fossil record is poor eg Flatworms viruses c Simple Molecular Clock Model i Changes at the molecular level accumulate at a constant rate ii Know rate iii Know number of changes iv Time v Molecular clocks must be calibrated