BIOEE 1780 Lecture Notes - Lecture 7: Phylogenetic Tree, Monophyly, Polyphyly
28 Apr 2018
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Lecture 7 – Phylogenetics I
Branches: lineages evolving through time that connect successive speciation or other branching events
Phylogeny: a visual representation of the evolutionary history of populations, genes, or species
• Tree Thinking: using data to construct trees, and reading trees to determine evolutionary
relationships
Extant Organisms: organisms that are still alive (i.e. not extinct)
Nodes: points in a phylogeny where a lineage splits (known as a speciation event)
• Speciation Event: occurs when population becomes subdivided to the point where individuals
between these subpopulations are no longer able to interbreed
Tips: the terminal ends of an evolutionary tree, representing species, molecules, or populations being
compared
Clades: single branches in the tree of life
• Each clade represents a common ancestor and all of its descendants.
The evolution of a new trait is indicated by a vertical line crossing the root of the clade:
Monophyletic Group: a clade (i.e. a common ancestor and all of its descendants)
Polyphyletic Group: a taxon that doesn't include the common ancestor of all members of the taxa
Paraphyletic Group: a group of organisms that share a common ancestor, but the group doesn't include
all of the descendants of that common ancestor
Mammals are monophyletic.
Characters: heritable traits that can be used to determine relationships
• Morphological characters
• Molecular characters
• Behavioral characters
Taxa (singular taxon): groups of organisms that form taxonomic units, such as a species or order
Synapomorphy: a derived trait that is shared by a group of related species; a shared, derived character
• Define clades of organisms
Outgroups: groups of organisms that are outside of the monophyletic group being considered
Homoplasy: a shared trait that isn't due to common ancestry
• Caused by either…
o Convergent Evolution: the independent origin of similar traits in separate evolutionary lineages
o Evolutionary Reversal (or Character Reversal): the reversion of a derived trait to a form
resembling its ancestral state
Document Summary
Branches: lineages evolving through time that connect successive speciation or other branching events. Phylogeny: a visual representation of the evolutionary history of populations, genes, or species: tree thinking: using data to construct trees, and reading trees to determine evolutionary relationships. Extant organisms: organisms that are still alive (i. e. not extinct) Nodes: points in a phylogeny where a lineage splits (known as a speciation event) Speciation event: occurs when population becomes subdivided to the point where individuals between these subpopulations are no longer able to interbreed. Tips: the terminal ends of an evolutionary tree, representing species, molecules, or populations being compared. Clades: single branches in the tree of life: each clade represents a common ancestor and all of its descendants. The evolution of a new trait is indicated by a vertical line crossing the root of the clade: Monophyletic group: a clade (i. e. a common ancestor and all of its descendants)
