Decoding Life's Origins: Understanding Phylogeny and Evolutionary Patterns

1. Chapter 26Phylogeny 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. • Are subject to changes.

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

9. Modern System

10. Goal of Systematics • To have Taxonomy reflect the evolution or phylogeny of the organisms.

11. Phylogenetic Tree • Branching diagram showing evolutionary relationships between organisms. • Recreation of Darwin’s Tree of Life.

12. Phylogenetic tree – Ex.

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

14. Phylogenetic tree – Ex. Ancestral Lineage Branch point

15. Question? • How to group taxa so that the phylogenetic relationships are correct ? • Use evidence to date, but the relationships (and trees) will change as new data is obtained.

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 or evolutionary events (Occam’s razor). • Branch lengths – suggest the closeness of the relationships and the time of branch points.

31. Assignments • Read Chapter 26 or 16 in Hillis • Friday – today • Monday – Chapter 26 • Exam 3 -Tuesday

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

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

35. Kingdom • Highest Taxonomic category in the Linnaeus system. • Old system - 2 Kingdoms 1. Plant 2. Animal

36. 5 Kingdom System • R.H. Whittaker - 1969 • System most widely used, but is changing.

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

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

40. 3 Domain System • Based on molecular structure for evolutionary relationships. • Prokaryotes are not all alike and should be recognized as two groups.

41. 3 Domains 1. Bacteria – prokaryotic. 2. Archaea – prokaryotic, but biochemically similar to eukaryotic cells. 3. Eucarya – the traditional eukaryotic cells.

43. Tree of Life

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