Phylogenetics Flashcards
What is a phylogenetic tree?
A graphical representation of evolutionary relationships among organisms or a group of them.
What is systematic taxonomy?
Organizes the diversity of living things in an evolutionary context
Would mean that classification would perfectly follow phylogeny = monophyletic groups (comprised of the most recent common ancestor and descendants)
What was Darwin’s Tree of Life?
An early phylogenetic tree showing how a genus of related species might originate by divergence from a starting point
What are the four aspects of the phylogenetic tree?
Topology - branching pattern
Branch lengths - drawn to scale to represent the inferred amount of change
Root - oldest point = indicates last common ancestor (often an outgroup)
Confidence - trees are only estimates (bootstrap values) = based on expert opinion
What data was used to build phylogenetic trees?
Traditionally - morphological features (number of legs/beak shape/anatomy)
Today - molecular DNA, RNA and protein data
What is a monophyletic group?
An ancestral species and all its descendants
In systematic = all valid taxonomic groups
What is a paraphyletic group?
An ancestral species and only some descendants
Not valid in systematic
An example of a paraphyletic group
The class Reptilia
Does not contain birds, but a monophyletic group would need to include both
What is a polyphyletic group?
A group of organisms that lack a common ancestor and are not valid in systematic
What are clades?
Groups that share derived characters and form a subset within a larger group
Characters must be homologous
What is homology?
Homologous characters inherited directly from a common ancestor
What is homoplasy?
Features have evolved independently in different lines due to convergent or parallel evolution
What is synapomorphy?
Shared derived character shared by all members of the clade
What is symplesiomorphy?
Shared ancestral character inherited from ancestors older than the last common ancestor
Mammals and vertebrates both have backbones
