Lecture 2 Systematics and Phylogenies Flashcards
What is Cladistics?
A method of classifying organisms based on common ancestry and evolutionary relationships
Nodes?
Represents a common ancestor in a phylogenetic tree
Clades?
Groups of organisms that include a common ancestor and its descendants
Taxa/Terminals?
End point of branches representing the species or groups
Internal Group
Set of species within the group being studied
External Group
Closely related to internal group but not a part of it
Sister group
Two clades that share an immediate common ancestor
Homology
Similarity between traits or features in different species due to common ancestry
Plesiomorphy
Ancestral trait shared by 2 or more taxa
Synapomorphy
A trait shared by two or more taxa and most recent common ancestor but not by more distant relatives
Autapomorphy
A derived trait unique to a single taxon
Monophyletic Group
Consists of ancestral species and all its descendants
Paraphyletic Group
Include common ancestor and some of its descendants
Convergence
Similar traits evolve independently in different lineages that do not share common ancestor. Arrive from similar environmental challenges.
Parallelism
Similar traits evolve independently in closely related lineages due to similar genetic and developmental pathways. Trait does not present in ancestor
Reversion
A derived trait reverts back to ancestral state
