Chapter 26 Notes
Chapter 26 Notes Life103
Popular in Biology of Organisms-Animals and Plants
Popular in Entomology
This 3 page Class Notes was uploaded by Courtney Potter on Friday September 4, 2015. The Class Notes belongs to Life103 at Colorado State University taught by Shane Kanatous; Graham Peers in Summer 2015. Since its upload, it has received 59 views. For similar materials see Biology of Organisms-Animals and Plants in Entomology at Colorado State University.
Reviews for Chapter 26 Notes
Report this Material
What is Karma?
Karma is the currency of StudySoup.
Date Created: 09/04/15
Chapter 26 Phylogeny And the Tree of Life 0 Phylogeny hierarchal structure showing how every life form is related through evolution Systematicsclassifying organisms and determining their evolutionary relationships 0 Molecular systematics using genetic data to infer evolutionary relationships 0 Problems 1 So many different ways to organize a tree based on large amounts of data sets and genomes for each species various combinations Phylogenies Show Evolutionary Relationships Taxonomy how organisms are classi ed and named Binomial Nomenclature 18th century Carolus Linnaeus published a taxonomic system based on resemblances between species 0 A two part scienti c name was formed 1 Genusgroup in which species belongs 2 Species Hierarcha Classi cation 0 Domain Kingdom Phylum Class Order Family Genus Species o Taxon taxonomic unit at any level of hierarchy Linking Classi cation and Phylogeny o Phylogenetic treebranching diagram that represents the evolutionary history of a group of organisms 0 Problems 1 A species gets placed in a genus not most closely related over evolution a species loses key feature shared by relatives 2 Tells us nothing about evolutionary relationships between groups 0 Sub Levels of Phylogenetic Trees 0 Branch points divergence of two evolutionary lineages from a common ancestor 0 Sister taxa groups of organisms that share an immediate common ancestor Rooted ancestral lineage found at beginning branch point 0 Basal taxon lineage diverging early in a group lies on branch originating from shared ancestor doesn t mean it hasn t evolved O o Polytomy branch point in which more than two descendant groups emerge Systematic Trees class order etc but NO ancestor just groups What We Can and Cannot Learn From Phylogenetic Trees 1 Intended to show evolutionary descent not phenotypic similarity 2 Branching sequence doesn t always show actual ages of particular species 3 Do not assume taxon on tree evolved from taxon next to it Phylogenies Inferred From Morphological And Molecular Data 0 Homologiesphenotypic and genotypic similarities due to shared ancestry 0 Degree of homologyhow closely genomes are related 0 Analogy similarity between organisms due to convergent evolution 0 Due to natural selection and environments producing similar adaptations in organisms from different evolutionary lineages 0 Look similar but internal anatomy is different 0 Homoplasies independently developed analogous structures Molecular Homologies align DNA sequences to see if species are closely or distantly related Shared Characters Help Construct Phylogenetic Trees Cladistics common ancestry used to classify organisms o Cladeancestral species and ALL its descendants 1 Monophyletic CLADE ancestral species and ALL its descendants 2 Paraphyletic GROUP ancestral species and some descendants 3 Polyphyletic GROUP distantly related species but NOT recent ancestor Shared Ancestral And Derived Characters 0 Shared ancestral character originates in the ancestor of the taxon Shared Derived Character not found in ancestor but found in clade o Outgroup group or species from evolutionary lineage that diverged before other in lineage Phylogenetic Trees With Proportional Branch Lengths Just because a group evolved over a larger period of time does not mean it hasn t evolved Max Par50m y and Max Likelihood 0 Max Parisomyinvestigate simplest explanation consistent with facts 0 Max Likelihood given set of DNA based on probability on how DNA sequence changes over time Genomes Document Organism39s Evolutionary History 0 DNA changes relatively slowly and can be used for investigating relationships in taxa 100000000 years ago Mitochondrial DNA evolves rapidly and is used to explore recent evolutionary relationships Gene Duplications And Gene Families 0 Duplication increases the number of genes in genome providing more opportunity for evolutionary change Orthologous genes homology occurs between genes found in different species 0 Only diverge after speciation Paralogous genes homology results from gene duplication with the same system Genome Evolution 1 Orthologous genes are shared by lineage that diverged long ago 2 Number of genes in a species doesn t increase through duplication at same rate as phenotypic complexity Molecular Clocks Measuring absolute time of evolutionary changes based on observation that some genes and genomes evolve at constant rates 0 Number of nucleotide substitutions in orthologous genes is proportional to time elapsed since they diverged from ancestor Paralogous number of substitutions is proportional to time since ancestral gene was duplicated New Data Changes Tree of Life 0 Horizontal gene transfergenes transferred from one genome to another through 1 Exchange of transposable elements and plasmids 2 Viral Infection 3 Fusions of organisms