1. Systematics and Phylogenetic Revolution
Chapter 23
Systematics and Phylogenetic Revolution
I. Systematics
II. Cladistics
Cladogram
III. Classification
Phylogenetic Relationships

2. All living organism share common characteristics
I. Systematics
All living organism share common characteristics
Composed of cells 
Metabolize
Respond
Reproduce
Evolve and adapt to environment

3. However there is tremendous diversity of life forms
Bacteria Whales Sequoia trees Etc.

4. Biologists group organisms based on shared characteristics.
Systematics: study of evolutionary relationships.
Phylogeny: hypothesis about patterns of relationship among species similarities and differences among species

5. Darwin postulated all species descended from single common ancestor depicting the history of life as branching tree - cladogram

6. Darwin called process “descent with modification”
Divergence
Groups after have new derived characters
Evolution
changes that occur over time that makes
life forms more suited for the environment
Common Ancestor
Gives rise to new groups

7. Key to interpreting Phylogeny is tricky. Things to investigate:
How recently do species share common ancestor?
Does the similarity accurately predict evolutionary relationship?
Did oscillating selection occur for a trait? Meaning did a trait evolve in one direction and back the other way?
Did convergent evolution take place?
Did evolution reversal occur? Where the species re-evolves characteristics of the ancestral species.

8. II. Cladistics
Derived character: similarity inherited from most recent common ancestor of an entire group
Ancestral character: similarity or trait that arose prior to common ancestor of group.
Cladistics: only shared derived characters are informative about evolutionary relationship. The variation must be identified as ancestral or derived. Character can be any aspect of phenotype:
Morphology
Behavior
Physiology
DNA sequence
E.g.
Hair coat is a shared derived feature of mammals
Lungs in mammals are an ancestral feature – present in amphibians and reptiles.

9. Lamprey
Shark
Salamander

10. Lizard
Tiger
Gorilla

11. X X X X X X X X X X X X X X X X X X X X X Construction of a Cladogram
Clade: species share common ancestor, indicated by shared derived traits.
Traits:
Organism
Jaws
Lungs
Amniotic Membrane
Hair
No tail
Bipedal
Lamprey
Shark
Salamander
Lizard
Tiger
Gorilla
Human X X X X X X X X X X X X X X X X X X X X X

12. Now the data from this chart is used to create a diagram called a cladogram.
Gorilla
Human
Tiger
Lizard
Bipedal
Salamander
No Tail
Shark
Hair
Lamprey
Amniotic Membrane
Cladograms can be constructed using all kinds of data:
Physical Structures
DNA Sequence
Behavior
Physiology
Lungs
Jaws

14. Classification: how species are placed into taxonomic hierarchy:
III. Classification
Classification: how species are placed into taxonomic hierarchy:
Domain – Kingdom – Phylum – Class – Order – Family – Genus – Species

15. Grouping of organisms based on phylogenetic relationships
Monophyletic group
Most recent common ancestor of group and all descendants (clade)

16. Paraphayletic group
Most recent common ancestor or group but NOT all descendants

17. Polyphyletic group
Does not include most recent common ancestor of all member of the group
NOTE: Taxonomic hierarchies are based on shared traits therefore they should show evolutionary relationships