1. Taxonomy To sort organisms into species To classify species into higher taxonomic levels A taxon is a taxonomic unit at any level; for example “Mammalia” is a taxon at the Class level (taxa = plural)

2. Taxonomy Species that appear to be closely related are grouped into the same genus (e.g., the leopard Panthera pardus; African lion Panthera leo; Tiger Panthera tigris) Similar genus are grouped into the same family, and so on…

3. Domain Kingdom Phylum Subphylum Class Order Family Genus Species Diversification

4. Taxonomy Classification system Domain Eukarya KingdomAnimalia PhylumChordata ClassMammalia OrderPrimates FamilyHominidae GenusHomo speciessapiens

5. Taxonomy The taxonomic system was developed by Linnaeus in the 1750’s Binomial (two part) system; Genus species The scientific name includes the species name Example: Homo sapiens or H. sapiens No 2 organisms can have the same scientific name and this name is the same everywhere in the world!

6. Taxonomy Scientific names are descriptive May describe unique characteristic, region where species is found, etc. Example: Humpback whale Megaptera novaeangliae –Magas = large –Pteron = wing –Novas = new –Angaliae = England

7. Taxonomy Common names can be deceiving… http://www.koala.net/media http://www.ticam.utexas.edu/images/grizzly.jpg “bear” “dolphin”

8. Taxonomy Scientific names may change over time Many hierarchies are being re-examined based on results of molecular analysis Linnaean taxonomy does not take into account evolutionary relationships Enter phylogeny and systematics…

9. Systematics The reconstruction and study of evolutionary relationships Phylogeny – an evolutionary tree; species grouped by how long they’ve shared a common ancestor Evidence for determining these relationships must come from shared homolagous characteristics

10. Phylogeny The evolutionary history of a group is presented graphically in phylogenetic trees In a phylogenetic tree: –Time goes from the bottom up –Read from bottom up, not left to right –Branch length = number of changes –Depicts evolutionary relationships!

11. Time

13. Remember: Read from the bottom up; not left to right!

14. These three versions convey the same information (phylogenies depict evolutionary relationships) Node 1: common ancestor of human and chimp Node 2: c.a. of human, chimp, and gorilla

16. Phylogenetic trees reflect hierarchical classification of taxonomic groups

17. Phylogeny Systematists prefer monophyletic taxa Monophyletic – a single ancestor gave rise to all species in that taxon (and to no species in any other taxa); “single tribe” A monophyletic group consists of a common ancestor and all its descendants

18. Monophyletic group Monophyletic group (indicated in pink) consists of most recent common ancestor and all of its descendents Common ancestor: “Archosaur”

19. Paraphyletic group Paraphyletic group (indicated by pink) consists of the most recent common ancestor and some (not all) of the descendents 1 descendent, the hawk, is excluded

20. Polyphyletic group Polyphyletic group (indicated in pink) does NOT contain the most recent common ancestor Birds and bats can be included because of morphological similarities (convergent evolution)

21. Monophyletic versus Paraphyletic and Polyphyletic groups

22. Old classification system for plants New classification system for plants

23. Phylogeny What evidence is used to reconstruct phylogeny? –Comparative anatomy –Morphology –Embryology –Protein comparisons –DNA comparisons Problems of homology versus analogy

24. Phylogeny Homology (homologous structures) – likeness due to common ancestor Analogy (analogous structures) – also known as “homoplasy”; likeness due to convergent evolution; functional constraint Analogous structures are the result of separate evolution

27. Comparative Biology Elongated canine teeth (saber teeth) evolved separately in different groups of carnivores

28. Cladistics Cladistics – only shared derived characters are used in determining evolutionary relationships Homoplasy (analogy) complicates cladistic analysis Species that share a common ancestor constitute a clade (a monophyletic group is a clade) Clades are hypotheses, just as phylogenetic trees are

29. Time clade

30. Cladistics Principle of parsimony – favors the hypothesis that requires the fewest assumptions (the phylogeny that requires the fewest evolutionary events is the best hypothesis) Simplest is best (Occam’s Razor)

31. Parsimony and Homoplasy Placement of frogs as closely related to salamanders requires that tail loss (in adults) evolved twice (homoplasy); if frogs are closely related to gorillas, then tail loss evolved once, but would also have to lose amniotic membrane and hair

33. Ancestral versus Derived characters Ancestral – dates back to common ancestor (found in common ancestor and all its descendents) Derived – feature of distinct taxon Hair is a shared derived feature of mammals, but so is a backbone; the presence of a backbone cannot help us distinguish mammals from other vertebrates The presence of backbone is a shared ancestral feature (also present in amphibians and reptiles)

36. Recommended Reading Dictionary of Word Roots and Combining Forms; Donald J. Borror Best $15 you can spend Compiled from Greek, Latin and other languages, with special reference to biological terms and scientific names