Phylogeny and Systematics (Part 6)

1. Phylogeny and Systematics (Part 6) Phylogeny and Systematics (Making “Trees of Life”) AP Biology Ms. Day

2. Macroevolution • studies focus on change that occurs at or above the level of species • The origin of taxonomic groups higher than species level How does this occur? • Evolution of new traits (novelties) • mass extinctions • Open adaptive zones (divergent evolution)

3. Intro to Phylogenetics • https://highered.mheducation.com/sites/9834092339/student_view0/chapter23/animation_-_phylogenetic_trees.html

4. Phylogeny What is phylogeny? • The evolutionary history of a group of organisms • Systematicsattempts to reconstruct phylogeny, by analyzing evolutionary relatedness • Use morphological and biochemical similarities • Molecular systematics uses DNA, RNA and proteins to infer evolutionary relatedness. • Different tools are used to reconstruct phylogenies called phylogentic trees.

5. Making Evolutionary “Trees”: Illustrating Phylogeny  2 Methods • Cladistics = BRANCHES NOT TIME RELATED • sorts primitive and shared derived characteristics • based on evolutionary relationships • Makes cladograms

6. Let’s review in groups…

7. Cladograms have clades • Aclade within a cladogram • a group of species that includes an ancestral species and all its descendants • Cladistics • the study of resemblances among clades

8. Cladistics • Each branch is called a clade https://www.youtube.com/watch?v=46L_2RI1k3k

9. WHY? WHY?

11. 2. Phenetics = BRANCHES ARE TIME RELATED • based on overall similarity (morphology) without regard for evolutionary relationships • based on how similar organisms look • REMEMER: • Organisms can develop similar features through converent evolution **Creates phylograms

12. Leopard Domestic cat Common ancestor • Each branch point • Represents the divergence of two species

13. Wolf Leopard Domestic cat Common ancestor • “Deeper” branch points • Represent progressively greater amounts of divergence; more closely related

14. length of a branch reflects # of genetic changes that have taken place in a particular DNA sequence in that lineage More changes here

15. Currently, scientists use • Morphological (anatomy), biochemical, and molecular comparisons to show evolutionary relationships in “trees” • Obtained through fossil studies, DNA technology and current organisms

16. Molecular systematics

17. Not all Similarities Represent Common Ancestry • Homologous structures indicate shared common ancestry • Homologous structures are therefore evidence of divergent evolution • Analogous structures are similar in function but not in evolutionary history • Analogous structures are evidence of convergent evolution It is not always easy to sort homologous from analogous structures

18. Analogous Structures

19. How to Make a Trees: Hypotheses

20. https://ccl.northwestern.edu/simevolution/obonu/cladograms/Open-This-File.swfhttps://ccl.northwestern.edu/simevolution/obonu/cladograms/Open-This-File.swf • A shared primitive character • a homologous structure that is shared by all groups you are trying to define • A shared derived character • A new evolutionary trait unique to a particular clade(s)/branch

21. Outgroups vs. Ingroups • Outgroup • Species or group of species that is closely related to the ingroup • Distinguishes between shared primitive and shared derived characteristics • Closely related to ingroup • Ingroup • the various species we are studying

24. A Cladogram What is the shared primitive characteristic? Notochord

25. http://www.cengage.com/biology/discipline_content/animations/cladogram_construction.htmlhttp://www.cengage.com/biology/discipline_content/animations/cladogram_construction.html • http://www.wwnorton.com/college/biology/evolution/ch/04/animations.aspx

26. Phylograms and cladograms trees are JUST hypotheses • Which is the most parsimonious tree? • the best hypothesis which requires fewest evolutionary changes Parsimony does not always work, nature does not always take the simplest course