1. Lecture 9: Evolution & Classification Because of how evolution occurs: Hierarchical, nested classification is natural There is ONE TRUE PHYLOGENY Based on interrelationships Life started at one point & diverged Origin Speciation

2. Study of Evolutionary History Taxonomy: classification (naming) Systematics: describes evol’nry relationships Assume: similarity in heritable characters signifies closeness of relationship Use characters to deduce relationships & classify

3. Types of Taxonomy Phenetic: Groups species by phenotypic similarity May use physical, immunological, or genetic traits Phylogenetic: Use evolutionary relationships How recently shared common ancestor Phenetic & phylogenetic taxonomy often give similar results More on this next class

4. Terminology Evolution occurs in two ways: 1.Anagenesis: directional change in a lineage 2.Cladogenesis: branching by speciation Rate & pattern of anagenesis + branching pattern True Phylogeny

5. Reconstructing Phylogenies Use: 1.Ancestral Character (Plesiomorph): Primitive Inherited with little or no change from ancestor 2.Derived Character (Apomorph) Recently changed Only CHARACTERS are PRIMITIVE, not SPECIES

6. Reconstructing Phylogenies Use Shared Characters: Because of PARSIMONY (smallest number of changes in phylogeny) Change takes time Change is unlikely Shared characters usually indicate close relationships

7. Shared Characters 1.Ancestral Homologies Character found in both taxa Character found in common ancestor Character not in all descendants 2.Derived Homologies Character found in both taxa Character found in common ancestor Character in all descendants of common ancestor

8. 3. Analogies: Characters have no common history Characters are not in common ancestor Characters developed independently CONVERGENCE May be evolutionary reversals to ancestral state - cause loss of info about relationships

9. A A A A A A A A A A A A A A Derived Homology Ancestral Homology Analogy - character A- character A - character A

10. More realistic example abcdef abcdefabcdef abcdef abcdef abcdef a b c d e f a= ancestral a= derived

11. Phylogenetic Groupings 1.Monophyletic Shared derived homologies Contains all the descendants of a common ancestor e.g. all birds 2.Paraphyletic Shared ancestral homologies Species with derived characters not included Some but not all descendants of a common ancestor e.g. fish; reptiles – missing birds, mammals

12. 3. Polyphyletic Analogies Common ancestor not in group Shared characters evolved independently e.g. vultures

13. Groupings A A A A A A A A A A A A A Monophyletic Paraphyletic Polyphyletic

14. Phylogenetic Reconstruction: Whales Sea-dwelling ~ 53.5 mya Descendants of Artiodactyla (even-toed ungulates) Rudimentary & vestigial characters common to land mammals (pelvic girdle, diaphragm, sensory structures) Intermediary fossils: Ambulocetus – the walking whale (47 mya)

15. Whale Phylogeny continued Paraxonic foot symmetry: characteristic of artiodactyla (axis passes b/w 3 rd /4 th digits) Molecular studies: closest to artiodactyla out of 48 mammals Not just related to artiodactyls they ARE artiodactyls Geochemical studies: move from FW to SW in tooth oxygen ratios

16. Recent evidence: hippos more closely related to whales than other artiodactyla Previous viewpoint Recent viewpoint