Phylogeny & Systematics Chapter 25

What you need to know! The taxonomic categories and how they indicate relatedness. How systematics is used to develop phylogenetic trees. The three domains of life including their similarities and their differences.

Phylogeny Phylogeny – evolutionary history of a species or group of species Sources of evidence: 1. Fossil Record 2. Systematics – classifying organisms and evolutionary relatedness A.Morphological homology B.Molecular homology

Systematics A. Morphological Homology –similarities due to shared ancestry (homologous structures) –determined by how two organisms appear Analogous structures can be misleading (convergent evolution NOT relatedness) B. Molecular Homology –Similarities in the DNA base sequences –Most accurate –20 billion + base pairs sequenced so far (1,000’s of species) – BLAST Lab

Taxonomy Carolus Linnaeus ( ) Mostly morphological (grouping, separating organism due to body plans) Latin based binomial nomenclature: Each species is ID’d by genus (capital letter) and species (lower case) –Canis familiaris, Canis lupus, Felix domestica, Homo Sapien

All organisms classified in a hierarchy TaxonMemoryWolf Domain (broad)DidEukarya KingdomKingAnimalia PhylumPhilipChordata ClassComeMammalia OrderOverCarnivora FamilyFromCanidae GenusGermanyCanis Species (specific)SingingLupus

Phylogenetic Trees

Cladistics Grouping organisms according to their phylogenetic (evolutionary) relationship Using comparative morphology (taxonomy), and DNA analysis Ancestral species placed on the bottom, with new features leading to novel descendents Displays divergent evolution by showing new characteristics and old shared characteristics

Cladogram

Evolutionary History in Genomes DNA changes over time (mutation) Different parts of the DNA molecule change at different rates: Genes for ribosomes changes slowly –Shows relatedness over 100’s of millions of years Genes for mitochondrial DNA evolves rapidly –Expresses recent evolutionary events

Molecular Clock Mutations occur at regular intervals based on probability and time Number of mutations (or differences) between the genes of species provides a time for when those species diverged

Domains – Universal Tree of Life