Vocabulary for Evolutionary Biology
I. Evolutionary Units
Replicator anything in the universe of which copies are made (Dawkins). Qualities of good replicators are longevity, fecundity and fidelity.
Interactors an entity that directly interacts as a cohesive whole with its environment in such a way that replication is differential (Hull). Dawkins prefers to call these "vehicles": any relatively discrete entity, such as an individual organism, which houses replicators and which can be regarded as a machine programmed to preserve and propagate the replicators that ride inside it.
Mendelian Gene A stretch of chromosome that is associated with phenotypic difference.
Molecular Gene A stretch of DNA that codes for a single polypeptide chain (classical); a DNA sequences that stores the information which specifies the order of monomers in a final functional polypeptide or RNA molecule, or a set of closely related isoforms.
Evolutionary Gene Any stretch of DNA that seqregates and recombines with appreciable frequency and can be replaced by an alternative sequence in future generations. This has largely been succeeded by: any heritable change in an input to development that can cause a difference in phenotypic adaptation. Alternatively, a heritable potential for a phenotypic trait.
Ontogeny - The origin and development of the individual organism.
Lineage a single line of direct ancestry and descent.
II. Trees in Phylogeny and Genealogy
Tree A representation of the branching pattern of relationships among a set of biological entitites that are related by descent from a common ancestor.
Clade A part of a tree consisting of an ancestral species and all of its descendants.
Clone An asexual counterpart, applied to organelles as well as whole organisms.
Taxon Any named group of organisms. Plural: taxa. In phylogenetic studies some workers prefer the term OTU (operational taxonomic unit) for the units under study.
Sister taxa Taxa that are each others closest relatives.
Cladistics Methodology for the construction of phylogenetic hypotheses represented in trees using only synapomorphies.
Apomorphy Derived character; a trait that differs from its state in an ancestor.
Synapomorphy Derived character shared by two or more taxa.
Plesiomorphy Character that retains the same state as in ancestors at least two generations in the past. Also sometimes called a primitive character or an ancestral trait.
Monophyletic Group A clade. An ancestor and all its descendants. Founded on synapomorphies.
Paraphyletic Group A grade. An ancestor and some of its descendants. Founded on symplesiomorphis, or shared ancestral traits.
Polyphyletic Group Often a grade. A group that includes lineages that are each more closely related to lineages not included in the group.
Convergence Independently derived similarity.
Polarity The direction of character change, from one state of a character or trait, to another. For example, from ancestral to derived.