cladistics

• Cladistics


  Method hypothesizing relationships among organisms based on shared, derived characteristics
• Synapomorphies


  Shared, derived characteristics indicating inheritance from a common ancestor
• Cladogram


  Phylogenetic tree summarizing results of a cladistics analysis
• Plesiomorphic


  Original state of a characteristic in cladistics
• Apomorphic


  Changed state of a characteristic in cladistics
• Quantitative phyletics


  Another term for cladistics, emphasizing numerical analysis
• Phylogenetic systematics


  Another term for cladistics, focusing on evolutionary relationships
• OTUs


  Operational Taxonomic Units grouped based on shared, derived characteristics
• Bifurcating pattern


  Cladistics assumption that lineages split into exactly two groups
• Outgroup


  Taxon outside the studied clade used to determine evolutionary relationships
• Homologies


  Similar characteristics inherited from a common ancestor
• Analogies


  Characteristics evolved through convergent evolution, not useful in phylogenies
• Character polarity


  Order of evolution for each characteristic in cladistics analysis
• Synapomorphies vs. symplesiomorphies


  Derived vs. original character states shared by taxa in cladistics
• Parsimony


  Method to resolve conflicts in cladistics analysis, favoring the simplest explanation
• Phylogeny


  Hypothesis of evolutionary relationships among taxa based on available data
• Convergent evolution


  Independent evolution of similar traits in unrelated organisms
• Evolutionary parallelism


  Separate evolution of similar traits in related organisms
• Polarity


  Determining ancestral trait absence or presence
• Clade


  Group of organisms with a common ancestor
• Conflicts


  Inconsistencies in grouping organisms
• Monophyletic


  Taxon with common ancestor and all descendants
• Paraphyletic


  Group missing some descendant taxa
• Polyphyletic


  Taxon with species from multiple ancestors
• Linnaean Classification


  Hierarchical taxonomic system
• Taxon


  Group of organisms at any level
• Node


  Point where branches split in a tree
• Branch


  Connection between nodes in a tree
• Common Ancestor


  Shared ancestor of two or more taxa
• Caminalcules


  Fictional organisms used for evolutionary analysis
• Binary Character


  Trait with two possible states
• Character Matrix


  Table showing character states of organisms
• Primitive Character


  Trait shared by all organisms, not useful for comparison
• Cladistic Analysis


  Method of classification based on shared characteristics
• Three assumptions in cladistics

  1. Change in characteristics occurs in lineages over time.

  2. Any group of organisms is related by descent from a common ancestor

  3. There is a bifurcating, or branching, pattern of lineage-splitting.