Evolutionary Biology: Phylogeny, Cladistics, and Molecular Evolution Terms

adaptive radiation

Rapid diversification of a lineage into various ecological forms.

anagenesis

Evolution within a single lineage over time without branching.

ancestral

A trait present in the common ancestor of a group.

branch

A line representing an evolutionary lineage on a tree.

character

A heritable trait or feature of an organism.

character states

The specific alternative forms of a character.

clade

A group consisting of an ancestor and all its descendants.

cladogenesis

The splitting of a single lineage into two or more distinct lineages.

classification

The arrangement of organisms into hierarchical groups.

common ancestors

An ancestral organism shared by two or more lineages.

derived

A trait that differs from the ancestral state.

divergence

The evolutionary separation or splitting of lineages.

divergent evolution

The accumulation of differences between closely related populations.

evolutionary reversal

The return of a derived trait to an ancestral state.

extinction

The complete disappearance of a species or lineage.

higher taxon

A taxonomic rank above species such as genus or family.

homologous

Traits shared due to common ancestry.

homoplasy

Traits shared independently, not due to common ancestry.

horizontal gene transfer

Transfer of genetic material between organisms other than by descent.

ingroup

The set of taxa of primary interest in a phylogenetic analysis.

internal nodes

Nodes on a tree representing ancestral populations.

last universal common ancestor (LUCA)

The most recent common ancestor of all current life.

lineage

A continuous series of ancestors and descendants.

molecular clock

Technique using mutation rates to estimate divergence time.

monophyletic

A group containing an ancestor and all its descendants.

most recent common ancestor (MRCA)

The most recent individual from which all organisms in a group descend.

outgroup

A taxon known to diverge before the ingroup in phylogeny.

parallel evolution

Independent evolution of similar traits in related lineages.

paraphyletic

A group containing an ancestor and some, but not all, descendants.

parsimony

The principle favoring the simplest phylogenetic tree.

phylogenetic tree

A diagram depicting evolutionary relationships.

phylogeny

The evolutionary history of a group of organisms.

polyphyletic

A group containing taxa derived from multiple ancestors.

root

The basal node representing the common ancestor of all tree taxa.

species tree

A tree depicting the evolutionary history of species.

synapomorphies

Shared, derived characters defining a clade.

taxon

A taxonomic group of any rank.

terminal nodes

The endpoints of a tree representing extant or extinct taxa.

convergent evolution

Independent evolution of similar traits in unrelated lineages.

crown group

The living representatives of a clade plus their MRCA.

gene duplication

Creation of an extra copy of a gene.

gene family

A set of several similar genes formed by duplication.

gene tree

A phylogenetic tree tracing the history of a gene.

incomplete lineage sorting

When gene trees do not match the species tree.

likelihood

Statistical measure of how well a tree explains data.

molecular evolution

Evolution at the level of DNA and proteins.

stem group

Extinct taxa more closely related to a crown group than others.

adaptation

A trait that enhances an organism's fitness in its environment.

character displacement

Evolutionary divergence when similar species co-occur.

Darwin's explanatory model

Natural selection based on variation, inheritance, and differential success.

evolutionary constraints

Factors that limit adaptive evolution.

exaptation

A trait currently useful for a function other than that for which it evolved.

fitness

An organism's ability to survive and reproduce.

frequency

The proportion of a particular item in a population.

generational process

Processes operating across generations.

heritable

Capable of being passed from parent to offspring genetically.

homology

Similarity resulting from common ancestry.

individual selection

Selection acting on differences among individuals.

levels of selection

Hierarchy of entities at which selection acts.

natural selection

Differential survival and reproduction due to phenotype differences.

neutral alleles

Alleles that do not affect fitness.

phenotype

The observable characteristics of an organism.

populational process

Processes acting on population-level variation.

preadaptation

A trait that fortuitously serves a new function before selection shapes it.

reproductive success

The passing of genes onto the next generation.

allele frequency

The relative proportion of a specific allele in a population.

alleles

Alternative forms of a gene.

codons

Sequences of three nucleotides coding for amino acids.

chromosome fission/fusion

Splitting or fusing of chromosomes affecting karyotypes.

duplication

The replication of a region of DNA.

exons

Coding regions of a gene.

genes

Units of heredity made of DNA.

genetic code

Set of rules by which genetic information is translated.

genotypes

The genetic makeup of an organism.

Hardy-Weinberg equilibrium

Principle that allele frequencies remain constant without evolutionary forces.

heterozygosity

Having two different alleles at a given locus.

insertions/ deletions

Addition or removal of nucleotides in DNA.

introgression

Movement of genes from one species into another via hybridisation.

introns

Non-coding regions of a gene removed during transcription.

inversions

Reversals of chromosome segment orientation.

linkage disequilibrium

Non-random association of alleles at different loci.

locus

Specific physical location of a gene on a chromosome.

mutation rate

The frequency of new mutations per generation or locus.

mutations

Changes in the nucleotide sequence of DNA.

noncoding DNA

DNA regions that do not code for proteins.

nonsynonymous

Mutations that change the amino acid sequence.

pleiotropy

When one gene influences multiple phenotypic traits.

point mutation

Mutation affecting a single nucleotide base pair.

polymorphic

Having multiple variants or alleles at a locus in a population.

polyploidy

Having more than two complete sets of chromosomes.

recombination

Exchange of genetic material between non-sister chromatids.

recombination rate

Frequency at which recombination occurs per generation.

single nucleotide polymorphism

Variation at a single nucleotide position in DNA.

synonymous

Mutations that do not change the amino acid sequence.

absolute fitness

Total number of offspring produced by an individual.

adaptive landscape

Graphical representation of fitness across genotypes or phenotypes.

artificial selection

Human-directed selective breeding of organisms.

balancing selection

Selection that maintains multiple alleles in a population.

deleterious mutations

Mutations that reduce fitness.

evolutionary trade-off

Circumstance where an adaptation for one trait reduces another.