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

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

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

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

6. Further reading: https://www. khanacademy

7. 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

8. 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?

9. 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

10. 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

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

12. 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?

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

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

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

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

17. 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!

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