1. Phylogeny and Systematics (Part 6)
Phylogeny and Systematics (Making “Trees of Life”) AP Biology Ms. Day

2. Macroevolution
studies focus on change that occurs at or above the level of species
The origin of taxonomic groups higher than species level
How does this occur?
Evolution of new traits (novelties)
mass extinctions
Open adaptive zones (divergent evolution)

3. Intro to Phylogenetics
/student_view0/chapter23/animation_- _phylogenetic_trees.html

4. Phylogeny What is phylogeny?
The evolutionary history of a group of organisms
Systematics attempts to reconstruct phylogeny, by analyzing evolutionary relatedness
Use morphological and biochemical similarities
Molecular systematics uses DNA, RNA and proteins to infer evolutionary relatedness.
Different tools are used to reconstruct phylogenies called phylogentic trees.

5. Making Evolutionary “Trees”: Illustrating Phylogeny  2 Methods
Cladistics = BRANCHES NOT TIME RELATED
sorts primitive and shared derived characteristics
based on evolutionary relationships
Makes cladograms

6. Let’s review in groups…

7. Cladograms have clades
A clade within a cladogram
a group of species that includes an ancestral species and all its descendants
Cladistics
the study of resemblances among clades

8. Cladistics Each branch is called a clade

9. WHY?
WHY?

11. 2. Phenetics = BRANCHES ARE TIME RELATED
based on overall similarity (morphology) without regard for evolutionary relationships
based on how similar organisms look
REMEMER:
Organisms can develop similar features through converent evolution
**Creates phylograms

12. Represents the divergence of two species
Each branch point
Represents the divergence of two species
Leopard
Domestic cat
Common ancestor

13. “Deeper” branch points
Represent progressively greater amounts of divergence; more closely related
Leopard
Domestic cat
Common ancestor
Wolf

14. length of a branch reflects # of genetic changes that have taken place in a particular DNA sequence in that lineage
More changes here

15. Currently, scientists use
Morphological (anatomy), biochemical, and molecular comparisons to show evolutionary relationships in “trees”
Obtained through fossil studies, DNA technology and current organisms

16. Molecular systematics

17. Not all Similarities Represent Common Ancestry
Homologous structures indicate shared common ancestry
Homologous structures are therefore evidence of divergent evolution
Analogous structures are similar in function but not in evolutionary history
Analogous structures are evidence of convergent evolution
It is not always easy to sort homologous from analogous structures

18. Analogous Structures

19. How to Make a Trees: Hypotheses

20. A shared primitive character
ms/Open-This-File.swf
A shared primitive character
a homologous structure that is shared by all groups you are trying to define
A shared derived character
A new evolutionary trait unique to a particular clade(s)/branch

21. Outgroups vs. Ingroups Outgroup
Species or group of species that is closely related to the ingroup
Distinguishes between shared primitive and shared derived characteristics
Closely related to ingroup
Ingroup
the various species we are studying

24. What is the shared primitive characteristic? Notochord
A Cladogram
What is the shared primitive characteristic? Notochord

25. http://www.cengage.com/biology/discipline_co ntent/animations/cladogram_construction.html
lution/ch/04/animations.aspx

26. Which is the most parsimonious tree?
Phylograms and cladograms trees are JUST hypotheses
Which is the most parsimonious tree?
the best hypothesis which requires fewest evolutionary changes
Parsimony does not always work, nature does not always take the simplest course