1. Chapter 25 Phylogeny and the Tree of Life

2. Chapter focus
Shifting from the process of how evolution works to the pattern evolution produces over time.

3. Phylogeny Phylon = tribe, geny = genesis or origin
The evolutionary history of a species or a group of related species.

4. Systematics The study of biological diversity and classification.
Uses evidence from the fossil record and other sources to reconstruct phylogeny.

5. Systematics fuses:
1. Phylogeny- tracing of evolutionary relationships.
2. Taxonomy- the identification and classification of species.

6. Taxonomy Natural to humans.
Modern system developed by Linnaeus in the 18th century.

7. Scientific names Composed of Genus and species.
Written in Latin and shown in italics or underlined.
Governed by a set of rules and procedures.

8. Linnaeus Taxonomy
1. Binomial Nomenclature – two names for each organism.
Ex - Homo sapiens
2. Hierarchical System – arranges life into groups Ex - Kingdom  Species

10. Goal of Systematics
To have Taxonomy reflect the evolutionary affinities or phylogeny of the organisms.

11. Phylogenetic Tree
Branching diagram showing evolutionary relationships between organisms.

12. Phylogenetic tree - Example

13. Trees show: Ancestral lineage Branch points or nodes
Length of branch point suggests “time” and degree of closeness.

14. Phylogenetic tree - Example
Branch point
Ancestral Lineage

15. Question?
How to group taxa so that the phylogenetic relationships are correct ?

16. Ideal Situation
Monophyletic Grouping - a single ancestor gave rise to all species in the taxon.

18. Other Possibilities
Polyphyletic - grouping where members are derived from two or more ancestral forms.
Paraphyletic - grouping that does not include all members from an ancestral form.

20. Problem Not all “likeness” is inherited from a common ancestor.
Problem is of homology vs analogy.

21. Homology and Analogy
Homology – likeness attributed to shared ancestry.
Ex: forelimbs of vertebrates
Analogy – likeness due to evolution solution for the same problem.
Ex: wings of insects and birds

22. Convergent Evolution
When unrelated species have similar adaptations to a common environment. A specific example of Analogy.
Ex: Sharks and dolphins

23. Only 1 is a mole

24. Only one is a cactus

25. Need Methods to group organisms by similarities and phylogenies.
One possible method is Molecular Systematics.

26. Molecular Systematics
Compares similarities at the molecular level.
Ex: DNA, Proteins

27. DNA patterns
If similar DNA – more closely related, more recent common ancestor.
If different DNA – less closely related, less recent common ancestor.

29. Making a Phylogenetic Tree
May use morphology, genetic and other data.
Typically “rooted” in a common ancestor.
Uses statistical analysis looking for “best fit”.

30. Best Fit Maximum parsimony – requires fewest DNA base changes.
Branch lengths – suggest the closeness of the relationships and the time of branch points.

31. Evolutionary History Is in the organism’s genome.
Note – taxonomic relationships can be changed based on what the DNA tells us.

33. Result
Taxonomy will become Genealogies, reflecting the organism’s "Descent with Modification“.

34. Kingdom Highest Taxonomic category Old system - 2 Kingdoms 1. Plant
2. Animal

35. 5 Kingdom System R.H. Whittaker - 1969
System most widely used, but is changing.

37. Main Characteristics Cell Type Structure Nutrition Mode
Problems in Kingdom Monera and Protista

38. Current Views
Multiple Kingdoms – split life into as many as 8 kingdoms.
Domains – a system of classification that is higher than kingdom.

39. 3 Domain System
Based on molecular structure for evolutionary relationships.
Prokaryotes are not all alike and should be recognized as two groups.

40. 3 Domains 1. Bacteria – prokaryotic.
2. Archaea – prokaryotic, but biochemically similar to eukaryotic cells.
3. Eucarya – the traditional eukaryotic cells.

44. Summary What is Phylogeny? What is a phylogenetic tree?
How is molecular data used in phylogeny?
Know the Domains and the Tree of Life.