Phylogeny

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BIOLOGY 3: Biodiversity
LECTURE 7 PHYLOGENY

Objectives: To recognize the characters used in phylogenies, To define homologous, analogous and homoplastic features, To interpret phylogenetic trees

Phylogeny
 refers to the evolutionary descent of taxa
 refers to the relationship between ancestors and descendants and relationships among descendant taxa
 shows the lineage of taxa and can be summarized in a branching diagram called is phylogenetic tree o Phylogenetic trees illustrate the evolutionary relationships among groups of organisms, or among a family of related nucleic acid or protein sequences Phylogeny Applications
 Tree of life – analyzing changes that have occurred in evolution of different organisms  Phylogenetic relationships among genes can help predict which ones might have similar functions (e.g., ortholog detection)  Follow changes occuring in rapidly changing species (e.g., HIV virus)  Phylogeny Packages o PHYLIP, Phylogenetic inference package  Felsenstein o PAUP, phylogenetic analysis using parsimony  Swofford Characters used in Phylogenies  Ancestral characters o states that are inherited unchanged from the ancestor o The character present in the ancestor which is also observed in the descendant taxon is an ancestral character. o Taxa with numerous ancestral characters are described as primitive.  Eg. Turtles (relic)  Derived characters o states that are inherited from the ancestor but already in modified form. A character present in the descendant taxon but has not been observed in the ancestor is derived character. o Taxa with numerous derived characters are described as advanced Determining whether a character is ancestral or derived:  Time element o this refers to the sequence of appearance of the character state o If the time of appearance among comparable character states can be determined, then the earlier evolved…...

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