Phylogenetic Classification – Key Vocabulary

A set of vocabulary flashcards covering essential terms and definitions from the lecture on phylogenetic classification, cladistics, and evolutionary relationships.

Cladistics

A method of classifying living organisms based on common ancestry, focusing on branching patterns of evolutionary trees (cladograms).

Clade

A group of organisms that includes a common ancestor and all of its descendants.

Node

A point on a cladogram where a single lineage splits into two or more lineages (branch point).

Derived Character

A trait present in an organism but absent in the last common ancestor of the group; used to infer evolutionary relationships.

Morphological Characters

Physical traits—such as bone structures or leaf shapes—used to determine evolutionary relationships.

Molecular Characters

DNA, RNA, or protein sequence data used for phylogenetic analysis.

Behavioral Characters

Inherited patterns of behavior that can be used as traits in cladistic studies.

Apomorphy

A derived trait that is unique to a particular group of species.

Plesiomorphy

An ancestral trait retained by a taxon throughout evolution.

Autapomorphy

A derived trait found in only one taxon and absent in its closest relatives.

Synapomorphy

A shared derived trait particular to an entire clade, indicating common ancestry.

Homoplasy

A character state shared by at least two organisms but not present in their common ancestor (often due to convergent evolution).

Cladogram

A diagram (concept map) that shows evolutionary relationships; branch order reflects sequence of divergence events.

Outgroup

A taxon included in a cladogram for comparison; helps to root the tree and determine character polarity.

Phylogenetic Tree

A diagram representing evolutionary relationships among organisms; depicts hypotheses about how species evolved from common ancestors.

Monophyletic Group

A group that includes an ancestor and all of its descendants (a true clade).

Paraphyletic Group

A group that includes an ancestor and some, but not all, of its descendants.

Polyphyletic Group

A grouping that does not include the most recent common ancestor of its members.

Homologous Structure

Structures in different species that are similar due to common ancestry; similar in structure and origin, but may differ in function.

Analogous Structure

Structures in different species that are similar due to convergent evolution, not common ancestry; similar in function but different in structural origin.