9_PhylogeneticSyst - Phylogenetic Systematics 25.1-25.3 Molecular systematics is revealing surprises 2 More surprises Eukarya Archaea Bacteria 3 Some

9_PhylogeneticSyst - Phylogenetic Systematics 25.1-25.3...

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Phylogenetic Systematics 25.1-25.3
2 Molecular systematics is revealing surprises!
3 More surprises! Eukarya Archaea Bacteria
4 Some definitions… Phylogeny = the evolutionary history of a species or group of related species Systematics = study of the diversity and relationships of organisms Taxonomy = the science of classifying living things Phylogenetic systematics = classification of organisms by their order of branching on an evolutionary tree
5 Phylogenies are based on common ancestries inferred from various types of evidence including: Fossils Morphology Molecules (DNA and protein)
6 Fossils reveal ancestral characteristics and the timing of events
7
8 Morphological and Molecular Homologies In addition to fossils, phylogenetic history can be inferred from morphological and molecular similarities in living organisms Organisms with very similar morphologies or similar DNA sequences are likely to be more closely related than organisms with vastly different structures or sequences
9 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
Homologous structures
11 Analagous (convergent) structures
12 Analogous structures or molecular sequences that evolved independently are also called homoplasies
1 2 1 2 Deletion Insertion 1 2 1 2 Computer alignments are used to find homologous DNA regions

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