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Taxonomy & Phylogeny Classification of Organisms.

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Presentation on theme: "Taxonomy & Phylogeny Classification of Organisms."— Presentation transcript:

1 Taxonomy & Phylogeny Classification of Organisms

2 Classification What characters are suitable for classification Systematics –Combination of taxonomy & phylogeny –Systematic approach to understanding evolutionary relationships among organisms

3 Hierarchical Classification System Taxa –Major groupings or categories –Nested set of increasing inclusiveness Domain Kingdom Phylum Class Order Family Genus Species

4 Cladistic Tree of Life

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6 Wittikers 5 Kingdom Classification Scheme

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9 Taxonomic Rules Binomial nomeclature –Genus species –Genus name is noun –species name is adjective –Higher taxonomic levels (families, orders, etc..) are also nouns

10 Taxonomy Relates to Phylogeny Taxonomic characters allow phylogenetic grouping Useful taxonomic characters –Morphological –Molecular (biochemical) Chromosomal Proteins DNA Homologies –Character similarities attributed to common ancestry

11 Using Taxonomic Characters to Construct Phylogenies Ancestral character state –The form of the trait present in the most recent common ancestor of the groups being considered Derived character state –The variant forms of the trait present in the members of the groups being considered Polarity –Relationship of character trait state to ancestral state

12 Example of Polarity Determination Study group –Amniotes – animals with amniotic membrane around developing embryo –Birds, Reptiles, Mammals Character being studied –Dentition – teeth Character states –Present –Absent Question: Is dentition a derived or ancestral trait for amniotes? Outgroup comparison –Phylogenetically close group, but non-amniote

13 Example of Polarity Determination teeth no teeth MammalsBirdsReptiles Amniote Amphibians &Fish Non-Amniote Outgroup has teeth –therefore teeth are considered ancestral & be presumed to occur in most recent common ancestor of amniotes and non-amniotes Teeth in amniotes is an ancestral character state Loss of teeth in birds is a derived state teeth Common Ancestor

14 Cladograms Clade –Groups of organisms that share derived character states Synapomorphy –Shared, derived character Cladogram –Nested, hierarchical assembly and representation of clades

15 Phylogenetic Relationships Established by Comparison of Multiple Characters

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17 Cladograms vs Phylogenetic Trees Cladogram –Lacks information duration of lineages Amounts of evolutionary change Phylogenetic tree –Establishes extinct vs extant lineages –Indicates evolutionary timescale & degrees of change Length of lines or numerical indications

18 Molecular Phylogeny Human Comparison of cytochrome c mutations

19 Phylogenetic Groupings Monophyletic –All descendents and most recent common ancestor Paraphyletic –Leaves out some descendents from a recent common ancestor Polyphyletic –Arbitrary groupings which do not include common ancestors

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23 Cladistics & Cladograms vs Traditional Taxonomy Cladistics –Taxonomic groupings based solely on establishing monophyletic relationships –Cladograms establish monophyletic taxonomic levels Traditional taxonomy –Common descent – phyletic relationship –Adaptive evolutionary change – ecological zones

24 Fig. 32.7

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