Systematics and Phylogeny Vocabulary

Vocabulary flashcards reviewing key concepts, definitions, and cladogram groupings from the lecture on Systematics and Phylogeny.

Taxonomy

The scientific discipline concerned with naming and classifying organisms.

Systematics

The theory and practice of classifying organisms based on their evolutionary history (phylogeny).

Phylogenetic Tree

A branching diagram that represents a hypothesis about evolutionary relationships among species or groups.

Branch Point

A node on a phylogenetic tree representing the divergence of two evolutionary lineages from a common ancestor.

Sister Taxa

Groups of organisms that share an immediate common ancestor.

Rooted Tree

A phylogenetic tree that includes a branch representing the last common ancestor of all taxa in the tree.

Basal Taxon

A lineage that diverges early in the history of a group and represents the common ancestor of the group.

Polytomy

A branch point in a phylogenetic tree from which more than two descendant groups emerge, indicating unresolved evolutionary relationships.

Cladogram

A phylogenetic tree format depicting only the order in which different clades arose, where branch lengths convey no information.

Phylogram

A phylogenetic tree in which branch lengths depict evolutionary patterns, proportional to evolutionary change or chronological time.

Homology

Phenotypic and genetic similarities among organisms that are due to shared evolutionary ancestry.

Analogy

Similarity between organisms due to convergent evolution rather than shared ancestry.

Convergent Evolution

The process where similar environmental pressures and natural selection produce similar adaptations in organisms from different evolutionary lineages.

Homoplasy

An analogous structure or molecular sequence that evolved independently in separate lineages.

Ingroup

The set of taxa whose evolutionary relationships are being actively studied.

Outgroup

One or more taxa related to the ingroup that diverged earlier, used as a reference point to root the tree and distinguish ancestral from derived traits.

Character

An anatomical, physiological, or molecular feature used to compare taxa across phylogenetic studies.

Character State

The observed variation of a character in a organism or taxon, such as presence or absence.

Cladistics

A method of classification that groups organisms based on common descent and shared derived characters.

Clade

A group of taxa that includes an ancestral species and all of its descendants.

Monophyletic Group

A group consisting of an ancestral species and all of its descendants.

Paraphyletic Group

A group consisting of an ancestral species and some, but not all, of its descendants.

Polyphyletic Group

A group that includes distantly related species but does not include their most recent common ancestor.

Shared Ancestral Character (Symplesiomorphy)

A character that originated in an ancestor of the taxon or clade.

Shared Derived Character (Synapomorphy)

An evolutionary novelty unique to a particular clade.

Maximum Parsimony

A principle assuming that the phylogenetic tree requiring the fewest evolutionary events (molecular changes or character additions) is the most likely.

Maximum Likelihood

A principle stating that, given rules about how DNA changes over time, a tree can be found reflecting the most likely sequence of evolutionary events.