1. PHYLOGENY and the TREE of LIFE Chapter 26

2. Phylogeny and Systematics • Phylogeny -- Evolutionary history of a species or group of related species; attempts to trace macroevolution. • Macroevolution – Origins of broader groups of organisms; studied in relation to major events of environmental change. • Systematics -- Study of biological diversity in an evolutionary context. • Current biological diversity reflects past episodes of speciation and macroevolution. • Taxonomy – Component of systematics which includes identification and classification of species.

3. Taxonomy and Classification • System used today was developed by Carl Linnaeus in the 18th century. • Two main features: 1) sort and name separate species, and 2) organize them into categories based on relationships. • Binomial nomenclature:Two-part Latin name unique to each species. • Ex: Genus Felis includes many species of related organisms (cats). • Species Felis silvestris; Felis lynx; Felis leo.

4. Broader categories of classification • Kingdom • Phylum (phyla, plural) • Class • Order • Family • Genus (genera, pl) • Species • Animalia • Chordata • Mammalia • Carnivora • Canidae • Canis • Canis familiaris

5. Kingdoms • 5 kingdom system • Monera (bacteria) • Protista (algae and protozoans) • Fungi • Plantae • Animalia • 6 kingdom system • Archaebacteria • Eubacteria • Protista • Fungi • Plantae • Animalia

7. Tools of Taxonomy • Outward similarities; embryonic development; life cycle stages. • Homology – similarities due to common ancestry. • But superficial features don’t always reflect evolutionary relationships. • Analogy -- Similarities due to convergent evolution, not common ancestry. • Convergent evolution -- Similar characteristics due to sharing similar ecological roles; natural selection shapes adaptations.

8. Homologous Structures

9. Convergent Evolution

10. Other Methods • Phenetics: makes no evolutionary assumptions. • Comparison is made of as many phenotypes as possible. • If enough characteristics are compared, homology will overshadow analogy.(?) • Overall phenotypic similarity is not a reliable indicator of phylogeny.(?) • This may be more useful for analyzing DNA sequence data.

11. Phenetics

12. DNA Sequencing

13. Other Methods continued • Cladistics: classifies organisms according to phylogeny. • Cladogram -- a branching “family tree”. • Each species in the cladogram has a mixture of primitive characters that existed in the common ancestor and characters that evolved more recently. • A major difficulty in cladistics is finding appropriate categories for each branch point.

14. Cladogram