Phylogenetic tree: visual representation of the hypothesized evolutionary relationships between different species or groups over time

Phylogenetic Tree Components Nodes (branch points): represent common ancestors

Phylogenetic Tree Components Branches: represent the relationship between nodes/species

Phylogenetic Tree Components Branches: represent the relationship between nodes/species Note: truncated branches represent extinctions

Further reading: https://www. khanacademy

Phylogenetic Tree Components Nodes (branch points): represent common ancestors Branches: represent the relationship between nodes/species Derived traits: traits different from the ancestor of the group or species; mapped directly onto branches Time branch node derived trait

Phylogenetic Tree Components Practice: For C and E: Where is their common ancestor? What traits do they share? What trait(s) differentiate them? Are whiskers in B and E homologous or analogous?

Phylogenetic Tree Components Derived traits: traits different from the ancestor of the group or species; mapped directly onto branches Clade (monophyletic group): group of species including one ancestor and all its descendants Time

Phylogenetic Tree Components Derived traits: traits different from the ancestor of the group or species; mapped directly onto branches Clade (monophyletic group): group of species including one ancestor and all its descendants The “one-snip” rule

Phylogenetic Tree Components Practice: What clades can you form that include C? Do C and D make a monophyletic group? Why or why not?

Cladogram Activity Steps: Can you come up with a different tree? Brainstorm important traits Make data table Make tree, adding one trait at a time Can you come up with a different tree? Which tree is most parsimonious?

Ingroup and Outgroup Ingroup: clade of interest Outgroup: “group of organisms not belonging to the group whose evolutionary relationships are being investigated” (Wikipedia)

Parsimony (Occam’s razor) Bigfoot (new species of manlike ape) or man in a costume?

Parsimony (Occam’s razor) The simplest explanation is most likely to be correct… Unless evidence is given otherwise

Parsimony (Occam’s razor) Most parsimonious tree Has fewest appearances or disappearances of traits Most probable

Parsimony (Occam’s razor) The more traits you map, the more certain you can be that your tree is accurate. Modern genetic analysis  unlimited traits!

Vocabulary so far Phylogenetic tree Node Branch Common ancestor Homologous trait Analogous trait Derived trait Clade (monophyletic group) Ingroup Outgroup Parsimony