Cladistics Flashcards
What is Cladistics?
- Use of cladograms
- Evolutionary relationships
- Relies on SHARED DERIVED CHARACTERS
What is a clade?
Groups with a common ancestor and all descendants (living and extinct)
What do the branches represent on cladograms?
Represents evolutionary time
Monophyly
includes all extant organisms and common ancestors
OTI
Operational Taxonimic Units
- tips of cladistic branches
- families, genera, species
Cladogenesis
A new clade is created
- divergence of two species
- junction between branches
- nearest common ancestor before divergence
Anagenesis
Species changes overtime, fails to diverge into separate species
- entire population changes together
Sister Taxa
Divergence of species
- species, genera, or families with a common ancestor
Outgroup
Branch evolved from distant common ancestor of a clade
- possess ancestral character states
- determines direction of evolution
Synapomorphies
- shared derived characters
- unique to a clade
- separate from sister clade
Symplesiomorphies
- ancient characters shared by many groups
- inherited from ancestors older than common ancestor
- shared primitive characteristics
Parsimony
Simplest scientific explanantion that fits the evidence
- fewest evolutionary changes
Polyphyletic
Cladistic grouping where animals belong to a single taxa
- don’t share common ancestor
- may exclude recent divergences
Paraphyletic
Cladistic relationship where organisms and recent common ancestor group together
- excludes some descendants
Monophyletic
Includes all extant organisms and common ancestors
