BIOL 2200 Lecture 10: 2-08 Lecture Notes

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Lecture 10 Notes
Introduction to Phylogenetics
Classic Classification System
o Binomial Nomenclature, started by Carolus Linnaeus
Tree thinking
o Phylogeny: a visual hypothesis of the evolutionary history of a group of species,
populations or genes
Connecting classification and phylogeny
o Phylogeny shows how organisms are related based off of change in
characteristics (evolution)
Genealogy family trees
o Close relation to sister, the relatedness comes from parent (common ancestor)
Parts of the phylogenetic tree
o Tip on the left is the root, the common ancestor that all of the organisms share
o Branches
o Nodes/ Branching points point where branches are split into more branches
o Clades A-C, B-C, A-F
o B and C are sister taxa, closest relative
o Polytomy when there is no yet known evolutionary relationship between taxa
o Ancestral --------------------------- Derived species (with traits that have emerged
more recently)
Rooted vs. Unrooted
o Unrooted tree the origin is unclear
Relationships are not linear
o Each branching point can be points of rotation
3 Key Points about Phylogeny
o Shows pattern of descent, not similarity
o Order of branching tells us relative age only
o But some phylogenetic trees estimate time since divergence
o Proximity of two taxa does not mean one originated from the other
Different Groups of Species
o Clade (monophyletic group) group of taxa that includes an ancestor and all of
its descendants (Group 1)
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