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Phylogenetics

Uploaded: 4 years ago
Contributor: Unique Salonga`
Category: Biology
Type: Lecture Notes
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Filename:   Phylogenetics.ppt (4.25 MB)
Page Count: 27
Credit Cost: 5
Views: 23
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Supot  may ari ng website putangina
Transcript
Phylogeny and the Tree of Life Systematics Taxonomy (classification) Phylogenetics (evolutionary history) Systematics: classifying organisms and determining their evolutionary relationships Tools used to determine evolutionary relationships: Fossils Morphology (homologous structures) Molecular evidence (DNA, amino acids) Animals and fungi are more closely related than either is to plants. Who is more closely related? Taxonomy: science of classifying and naming organisms Binomial nomenclature (Genus species) Naming system developed by Carolus Linnaeus. REMEMBER!! Dear King Philip Came Over For Good Spaghetti Dear King Philip Crossed Over Five Great Seas Dear King Philip Came Over From Germany Stoned Your own??? Phylogenetic Tree Branching diagram that shows evolutionary history of a group of organisms The topology is the branching structure of the tree. Tips represent groups of descendent taxa known as the tips or external nodes. Internal nodes occur at the points where more than one branch meet and represent the (usually inferred) ancestral sequences.  Root is a very important internal node representing the most recent common ancestor of all sequences in the phylogeny. Clade = group of species that includes an ancestral species + all descendents Shared derived characteristics an evolutionary novelty unique to a clade. Shared ancestral characteristics a character that originated in an ancestor of the taxon. Turtle Leopard Hair Amniotic egg Four walking legs Hinged jaws Vertebral column Salamander Tuna Lamprey Lancelet (outgroup) Cladogram NESTED CLADES University of California Museum of Paleontology's Understanding Evolution Monophyletic (from the Greek, meaning “single tribe”) consists of an ancestral species and all of its descendants Paraphyletic (“beside the tribe”) consists of an ancestral species and some, but not all, of its descendants Polyphyletic (“many tribes”) includes distantly related species but does not include their most recent common ancestor Monophyletic, paraphyletic, and polyphyletic groups Constructing a phylogenetic tree A 0 indicates a character is absent; a 1 indicates that a character is present. An outgroup is a species or group of species from an evolutionary lineage that is closely related to but not part of the group of species that we are studying (the ingroup) Branch lengths can represent genetic change Branch lengths can indicate time Draw a phylogenetic tree based on the data below. Draw hatch marks on the tree to indicate the origin(s) of each of the 6 characters. Answer: Interpreting patterns of relatedness Unrooted tree Circular (rooted) tree Rooted tree Various tree layouts Principle of maximum parsimony: use simplest explanation (fewest DNA changes) for tree – “keep it simple” Molecular clocks: some regions of DNA appear to evolve at constant rates Estimate date of past evolutionary events Maximum Parsimony (MP) choose tree that minimizes number of changes required to explain data Maximum Likelihood (ML) under a model of sequence evolution, find the tree which gives the highest likelihood of the observed data Tree of Life 3 Domains: Bacteria, Archaea, Eukarya SYSTEMATICS Biological diversity taxonomy Identification of species binomial Genus, species D K P C O F G S phylogeny classification cladistics Homologous similarities fossils molecular morphology focuses on

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