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Cladistics. Phylogeny. Study of evolutionary relationships. Cladistics. A method that applies the scientific method to the construction of evolutionary relationships. Cladogram. Diagram showing how organisms are related base on shared, derived characteristics. = derived characteristics.
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Phylogeny • Study of evolutionary relationships
Cladistics • A method that applies the scientific method to the construction of evolutionary relationships
Cladogram • Diagram showing how organisms are related base on shared, derived characteristics = derived characteristics
Cladogram Vocabulary • Ingroup • A group of species we are interested in • Outgroup • A species that is most closely related to an ingroup • Node • The point at which species diverge
DNA • With current DNA sequencing techniques, cladograms show amazing relationships
Constructing a Cladogram • Determine characteristics to analyze • Analyze characteristics of species • Build your cladogram! • The species with the fewest shared derived characteristics is your outgroup • Follow the rule of maximum parsimony (the shortest number of steps or character state changes is most likely correct)
Example: • Copy and complete the table below (mark “x” if an organism contains the character, leave the box blank if it does not):
Organism with the least number of traits goes at the bottom (less related to the rest) • Organism with the most traits goes at the top (more related to the rest)
Add the derived characters (traits) where appropriate Earthworm Trout Lizard Human Backbone
Earthworm Lizard Human Trout Hair Legs Backbone