BI111 Lecture Notes - Lecture 12: Phylogenetic Tree, Monophyly, Polyphyly

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1 Feb 2017
BI111- Lecture 12 January 30th, 2017- Biological Diversity and Population
Ancestral and Derived Structures
Individuals show evidence of Mosaic Evolution (Evidence of a common ancestor)
o Past is always changing
Combination of ancestral and derived characters in Evolutionary Lineage
Derived characters determined from fossils and embryos
Derived (Not all derived traits are adaptations, or something different that isn’t found in
the common ancestor) characters appear later in development (Derived traits from
Outgroup comparison for derived characters (Outliers possess traits that did not derive
from focused species)
Cladistic Phylogenies Based on…
Principle of Monophly
o All groups in a clade includes a common ancestor and all of its descendants
o Unless other data suggests that its more complicated
Principle of Parsinomy
o Simplest explanation most likely to be correct
All phylogenetic trees are hypotheses that attempt to accurately reflect historical events
Principle of Monophyly
Monophyletic Taxon- Includes an ancestral species and all of its descendants
Polyphyletic Taxon- Includes species from different evolutionary lineages
Paraphyletic Taxon- Include an ancestral species and only some of its descendants
Principle of Parsinomy (Guiding Principle- Every tree is different because it is a hypothesis)
Occam’s Razor
o Simplest explanation most likely be correct
o Unless other data suggest more complicated explanation
Evolutionary change is an unlikely event
o Evolution of character twice is extremely unlikely
o Evolutionary trees with derived characters appearing once are most parsimonious
A phylogenetic tree is a hypothesis
Convergent Evolution and Parsinomy
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