BIOL 1521 Lecture Notes - Lecture 1: Synapomorphy, Paraphyly, Ribosomal Rna
Phylogenetic Trees
Constructing Phylogenetic Trees
• Morphological data
o Structural features
o Organs
o Skeletal arrangements
o Developmental features
• Homology
o Similarity due to common ancestry
o Synapomorphies
• Traits shared by all descendants (and common ancestor)
• Define monophyletic groups
• Genetic data
o Mitochondrial DNA
o Ribosomal RNA
o Lots of different genes
• Parsimony
o The most likely pattern is the one requiring the fewest changes
• Trees are revised as we acquire more and better data
• An evolutionary lineage is a sequence of species that form a line of descent from a
common ancestor
Phylogenetic Groups
• Monophyletic group
o Group includes the most recent common ancestor of all those organisms (and no
others)
o All the descendants of that most recent common ancestor
• Paraphyletic group
o Omits some of the descendants of the most recent common ancestor
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