Topic 4: Systematics and Phylogeny Flashcards
Systematics
The theory and practice of classifying organisms based on evolutionary history.
Phylogeny
Shown as a phylogenetic tree which shows the evolutionary relationships among organisms.
Phylogenetic Trees
Demonstrates the evolutionary relationships between species and a common ancestor.
Branch Point (Node)
Represents the common ancestor of two lineages.
Dichotomous Branching
Divides into two branches
Speciation
The divergence of two species from a common ancestor.
Internal Branches
Connects two nodes
External Branches
Connect a node and a tip.
Basal Taxon
Diverges early and originates near the common ancestor.
Sister Taxa
Two descendants that split from the same node
Polytomy
A branch which more than two groups emerge. They lack sufficient data to determine lineages.
Root/Rooted
One branch that represents the common ancestor of all taxa.
Clades
Groups that include an ancestor and all its descendants
Types of Phylogenetic Trees
Cladograms and Phylograms
Cladograms
Depicts evolutionary relationships where only the branching pattern is important.
Phylograms
Depicts evolutionary patterns and branch length represents evolutionary change.
Homology
The trait was present i the common ancestor of the two organisms and retained overtime.
Analogy
The trait evolved independently in the two organisms as an adaptation to similar environments
Ingroup
The group whose evolutionary relationship you are studying
Outgroup
One or more taxa related to the ingroup but that diverged early.
Telling the difference between analogy and homology
Homo. have similar anatomy, developmental pathways in embryonic development, genetics, and can be traced back through history.
Trait Complexity
The more complex two similar structures are, the more likely they are homologous.
Characters (Traits)
anatomical, physiological, or molecular features used to compare taxa.
Character States
The observed variation of a character, which can be used to determine evolutionary changes
Cladistics
A method used to infer evolutionary relationships using homologous characters that group taxa based on shared derived characteristics.
Shared derived characteristics
Traits that evolved in the most recent common ancestor of a clade and are unique to that group.
Shared Ancestral Characters
Ancestral traits shared by a taxa of a clade but are also present in taxa of earlier clades.
Paraphyletic Grouping
consists of a common ancestor, but not all descendants of the ancestor.
Polyphyletic Grouping
Includes distantly related taxa but does not include the common ancestor of all group members.
