Lecture 9 - Chapter 25 - Phylogenetic Systematics

Lecture 9 - Chapter 25 - Phylogenetic Systematics - Fig....

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Phylogenetic Systematics the classification of organisms based on their evolutionary history 2 Fig. 26-3a Class: Mammalia Phylum: Chordata Kingdom: Animalia Archaea Domain: Eukarya Bacteria 3 Many recent surprises! Eukarya Archaea Bacteria The three-domain system : biological classification introduced by Carl Woese in 1990 Whole field of systematics is being revolutionized by the recent explosion of molecular techniques 4 Some definitions… • Phylogeny = the evolutionary history of a species or group of related species • The discipline of systematics classifies organisms and determines their evolutionary relationships (use fossil, molecular, and genetic data (DNA) to infer evolutionary relationships and homology) • Taxonomy = the science of classifying living things • Phylogenetic systematics = classification of organisms by their order of branching on an evolutionary tree
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5 Fossils reveal ancestral characteristics and the timing of events Two ways to evaluate… 6 Fossil record substantial but incomplete. • Typically hard fossils (e.g. dinosaur bones or human skull) • Also could be petrified wood, insects or impressions 7 Morphological and Molecular Homologies • In addition to fossils, phylogenetic history can be inferred from morphological and molecular similarities in living organisms • Organisms with similar morphologies or DNA sequences are likely to be more closely related than organisms with different structures or sequences 8 Sorting Homology from Analogy • In constructing a phylogeny, systematists need to distinguish whether a similarity is the result of homology or analogy • Homology is similarity due to shared ancestry • Analogy is similarity due to convergent evolution
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Homologous structures Determined by reconstructing phylogeny using independent characters Homologous structures can look very different. (Note: Often not easy to distinguish homology from analogy.) Pattern of some leaves developing into spines homologous.
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This note was uploaded on 10/03/2009 for the course BISC 120 at USC.

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Lecture 9 - Chapter 25 - Phylogenetic Systematics - Fig....

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