Taxonomy

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Taxonomy Phylogeny

• Classification of Organisms

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Classification

• What characters are suitable for classification
• Systematics
• Combination of taxonomy phylogeny
• Systematic approach to understanding evolutionary
  relationships among organisms

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Hierarchical Classification System

• Taxa
• Major groupings or categories
• Nested set of increasing inclusiveness

Domain Kingdom Phylum Class Order
Family Genus Species
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Cladistic Tree of Life
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Wittikers 5 Kingdom Classification Scheme
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Taxonomic Rules

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

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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

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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

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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

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Example of Polarity Determination
AmphibiansFish
no teeth
teeth
teeth
teeth
Amniote
Non-Amniote
Common Ancestor
teeth

• 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

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Cladograms

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

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Phylogenetic Relationships Established by
Comparison of Multiple Characters
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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

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Molecular Phylogeny

• Comparison of cytochrome c mutations

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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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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

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Fig. 32.7
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