Classification and phylogeny

1. Classification and phylogeny

2. Announcements • Assignment from lab 1 is due today in lab • Assignment for lab 2 include p23,24,27,28 and MacClade exercise (do it on data from exercise 2).

3. Classification and phylogeny • Concepts and terms • Why to study phylogeny • Constructing phylogentic tree (cladogram) • Classification • MacClade

4. Concepts and terms • Phylogeny. evolutionary history of a group of organisms (taxa) • Systematics study biological diversity of organisms and their evolution • Phylogenetic tree (Cladogram, dendrogram, phylogram). phylogeny of a group of organisms portrayed in a tree

5. Concepts and terms • Classification attaching names to organisms and group of organisms that may or may not reflect their phylogeny • Homology similarity b/c of having a common origin • Analogy similarity b/c of having a common function

6. Why to study phylogeny • Helps to deal with practical problems • Supply us with evolutionary information about -organisms -traits -when they evolved and their sequence -how many time they evolved (happened) -related species

7. Constructing Cladogram • Cladogram in P 15 & P18 • Derived character (1) derived (arose) within a group lineage • Ancestral character trait found in common ancestor (0) • Outgroup closely related but outside of the group of interest • Tree length sum of the number of evolutionary steps (events)

8. Constructing Cladogram Sister groups Sister groups B A C Other beetles dimples Short antennae Large size Eye spots on elytra Modified anal glands

9. Constructing Cladogram • Topology branching pattern of a phylogenetic tree • Characters conflicts due to homoplasy (trait evolved more than once) or evolutionary reversal • Cladistic approach (evolutionary path) and Maximum parsimony method (p 18) minimum number of steps to generate the phylogenetic tree

10. Constructing Cladogram • P 17 • Monophyletic (clade) common ancestor with all its descendants • Paraphyletic common ancestor with some but not all its descendants • polyphyletic unconnected species

11. Constructing Cladogram Paraphyletic Monophyletic polyphyletic

12. Constructing Cladogram • Good character is 1-Variable between species but not within a species 2-Easily measured and unambiguous 3-Shared derived characters is the key for a cladogram Example: page 23

13. Classification • Taxonomy :grouping and classification of organisms • Binominal or linnaean system ( E.coli ) • Species :group of organisms reproductively isolated from others • Genus :group of related species • Other categories (kingdom, phylum, class, order, family, genus, species) and any of this is called taxon

14. What to do • Look for the homologous shared derived character that you can use to construct a clade • Try more than one tree shape until you get the most parsimonious • Try different topologies (straw model)

15. Exercise 1 Characters or traits 1-head shape 2-head width 3-tip point 4-head notch 5-spiral thread 6-shank width 7-tight spiral

16. MacClade