1. Systematics and the Phylogenetic Revolution
Chapter 23

2. Systematics The Study of Evolutionary Relationships
Bases relationships of similarities
Does similarity always imply relation?

3. Cladistics
Makes relationships based on shared derived Characteristics NOT ancestral!
Ancestral vs Derived
Derived- Hair in mammals, because all mammals have it but not amphibians etc
Ancestral- Lungs all mammals have it but then so do some amphibians

4. How to construct a Cladogram
Step 1- Create a chart listing all organisms in question and traits that you would like to look at.
Trait
Dog
Fish
Human
Legs
Hair
BiPedal

5. Step 2- Mark off Traits that exist in each species
Dog
Fish
Human
Legs X
Hair
BiPedal

6. Step 3 – Construct Cladogram Using the traits you marked
Step 3 – Construct Cladogram Using the traits you marked. Animal with the most traits will be at the top of the Cladogram, animal with the least will be at the bottom.
Humans
Dog
Fish

7. Is it that Simple?
Nope!
Homoplasy- a shared character that has not been inherited from a common ancestor – can occur due to convergent evolution or evolutionary reversal
Frogs- Lack a tail but does that mean they are more closely related to humans than salamanders?

8. How do we draw our cladogram for the Frog?
Parsimony- draw the cladogram that requires the least number of changes

9. Creating a Phylogenetic Tree

10. Types of Phyla
Monophyletic-Consists of the most recent common ancestor and all of its descendants
Paraphyletic- Consists of the most recent common ancestor and some of its descendants.
Polyphyletic- Does not contain the most recent common ancestor of the group

11. Homologous vs Analagous Structures