Phylogenetic tree visual representation of the hypothesized evolutionary

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

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

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

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

Further reading: https: //www. khanacademy. org/science/high-school-biology/hs-evolution/hs -phylogeny/a/phylogenetic-trees

Phylogenetic Tree Components n n n 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: 1) For C and E: a) Where is their common ancestor? b) What traits do they share? What trait(s) differentiate them? 2) Are whiskers in B and E homologous or analogous?

Phylogenetic Tree Components n n 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 n n 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: 1) What clades can you form that include C? 2) Do C and D make a monophyletic group? Why or why not?

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

Ingroup and Outgroup n n 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) n n The simplest explanation is most likely to be correct… Unless evidence is given otherwise

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

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

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