Systematics and Phylogenetics Ch. 23.1, 23.2, 23.4, 23.5, and 23.7

1. Systematics and PhylogeneticsCh. 23.1, 23.2, 23.4, 23.5, and 23.7

2. Diversity Matters • Not all species, even closely related ones, interact with their environments the same way • Mosquitos and Plasmodia • Plasmodia causes malaria • Only 3:6 mosquito species can carry the disease and spread it • Understanding and categorizing species is important in all areas of biology • Systematics study of life’s diversity and all evolutionary relationships

3. Linnaeus System • Binominal nomenclature (two name system); uses genus and specific epithet (species name) to categorize similar species • Taxonomy groups species through different taxa (levels of similarity) • Domain most general; Bacteria, Archaea, Eukarya • Species most specific; Homo sapien • Names come from location of habitat, physical trait, scientist who discovered it, etc…

4. Taxonomic Hierarchy • Classification limited to more inclusive groups (taxa) as you specify the organism • Domain • Kingdom • Phylum • Class • Order • Family • Genus • Species • Subspecies

5. Phylogenetics • Just categorization is no longer important; now we are looking for the evolutionary connection between organisms • Phylogeny evolutionary history of a species • Phylogenetic tree visual representation of their phylogeny • Species at the base are common ancestors • Species in the branches are close variants

6. Anagenesis • Trees can be large; cover all known organisms • Trees can be small; cover only a specific genus • Trees can show specific changes through format • Straight lines show anagensis; gradual changes as a new species changes from the original population; no increase in biodiversity

7. Cladogenesis • Branching points depict two species diverging from a common ancestor; increase in biodiversity • Branches meet at their common ancestor • Branches can split again into “branchlets” which can form “twigs” • Every node (branching point) is the “root” for the generations that spring from it (clade) • Aves clade for birds • Birds of Prey nested clade inside Aves • Sister clads clades that share same node • Sister spices species that share the same node

8. Types of Phylogenetic Trees • Monophyletic • All species connected to one ancestral clade • Felidea clade all species of cat (tigers, house cat, lion, etc…) lead back to • Animalia clade all animals lead back too • Polyphyletic • Organisms of different clades but not their common ancestor • Vertebrates capable of flight (Birds and Bats); common ancestor (extremely ancient) not included

9. Types of Phylogenetic Trees 3) Paraphyletic • Clade of an ancestor but not all its descendants • Clade of birds and terrestrial dinosaurs; linkage to birds shown but not all descendants made by terrestrial dinosaurs • Depending on what information needs to be explained, this different types are necessary

10. Cladistics • Traditional systematics organizing trees based on morphology and evolutionary relationship • Popular up till the 1960s • Cladistics phylogenetic trees should reflect just evolution patterns of physical traits (characters; character states) • Ancestral character states original traits of the common ancestors • Derived character states new traits branching from the ancestral ones

11. Making a Cladogram • Cladistic method groups species into clade by shared derived characteristics; generate a cladogram • Hypothesized evolutionary connection • Node common ancestor • Branch monophyletic group; sometimes contain specific synapomorphies in clade • Molecular sequencing (protein, DNA, RNA) also used with synapomorphies comparisons • Help deal with convergent evolution, which presents false synapomorphies

12. Comparing Character States • Character states can be compared to each other in any number of ways • Often compared with other species that don't possess the character • Apomorphy derived character • Synapomorphy derived character found in multiple species • Shared characteristics shows species are part of the same clade • Markers for monophyletic lineages; adaptive radiation after major adaptation

13. Principle of Parsimony • Large cladograms, with 100s of species, have too many factors for humans to consider • Computer programs must be used to find the “best” cladogram • Principle of Parsimony simplest evolutionary history is the most likely; rare for many complex evolution events to have occurred • Molecular statistics have a major effect • Non-coding DNA, degenerate DNA codons, substitution rates of nucleotides all influence the statistical amount of mutation a population can experience

14. Statistics is the Key • Taking both fossil and evolutionary statistical data, two methods can be used to find the best cladogram • Maximum Likelihood Method • Data compared with other established cladogramsto find the “most likely” clade • Bayesian Method • Compares the distribution of character traits to the evolutionary model that would be needed for them to occur

15. Using Synapomorphies • Comparison of the species that do and do not have an apomorphy can organize the clade • Vertebral column in animals: • Most species of animals are invertebrates (no backbone) • Vertebrates (fish, mammals, birds, etc…) do have a backbone • Comparing the synapomorphies: • No backbone Ancestral • Backbone Derived

16. Using Synapomorphies to Support Data • If there is not enough data from fossils, apomorphies can still be compared with outgroup comparisons • Ingroup species in question with derived trait • Outgroup closely related species (not in clade) with ancestral trait • Butterfly legs groups of 6 and 4 • Outgroup comparisons show most insects have 6 legs • 6 legs ancestral • 4 legs derived

17. Using Molecular Data • Clades can have conflicting models that both have large support • Molecular comparing is sometimes the only method of categorizing group properly • Domains: Archaea, Bacteria, and Eukarya • All similar to each other in various ways • Evolution places Eukarya branching from Bacteria and Archaea branching from Eukarya • However, after their branching point, the transfer of some genetic material may have occurred (Horizontal gene transfer) through transformation, transduction, and even viral infections

18. Homework • Suggested Homework: • Test Your Knowledge • Actual Homework: • Discuss the Concepts #3 • Design the Experiment • Interpret the Data • Test Next Wednesday on Ch. 22, 23, and 24! • Final covers All chapters since mid-term (not 18 and 19)