BI111 Lecture Notes - Lecture 14: Polyphyly, Paraphyly, Mosaic Evolution

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17 Feb 2016
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Lecture 14 – Wednesday February 3, 2016
Ancestral and Derived Structures
Individuals show evidence of Mosaic evolution
Combination of ancestral and derived characters in evolutionary
lineage
Derived characters determined from fossils and embryos
Derived characters appear later in development
Outgroup comparison for derived characters
Cladistic Phylogenies Based On
Principle of Monophly
oAll groups in a clade includes a common ancestor and all of
its descendants
Principle of Parsimony
oSimples explanation most likely to be correct
oAll phylogenetic trees are hypotheses that attempt to
accurately re!ect historical events
Principle of Monophyly
Principle of Parsimony
Principle of parsimony (Occam’s razor)
oSimplest explanation most likely to be correct
oUnless other data suggest more complicated explanation
Evolutionary change is an unlikely event
oEvolution of character twice is extremely unlikely
oEvolutionary trees with derived characters appearing once
are most parsimonious
A phylogenetic tree is a hypothesis
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