Evolution Glossary

Term	Definition
Abiogenesis	Origin of life from non-living chemical processes
Allele frequency	Proportion of one specific allele in a gene pool
Allopatric speciation	Speciation through geographic isolation
Analogous organs	Same function, different embryonic origin; convergent evolution
Bottleneck effect	Genetic drift after catastrophic population reduction
Chemical evolution	Theory that life arose from inorganic molecules through chemical reactions
Convergent evolution	Independent evolution of similar traits in unrelated species
Directional selection	Selection favouring one extreme phenotype
Disruptive selection	Selection favouring both extreme phenotypes simultaneously
Divergent evolution	Divergence of related species from a common ancestor
Founder effect	Genetic drift in a population started by a small founding group
Gene flow	Transfer of alleles between populations via migration
Genetic drift	Random changes in allele frequency due to chance events
Genotype frequency	Proportion of a specific genotype in a population
Hardy-Weinberg equilibrium	Mathematical state where allele frequencies remain constant across generations
Homologous organs	Same embryonic origin, different function; divergent evolution
Macroevolution	Large-scale evolution producing new species and higher taxa
Microevolution	Small-scale changes in allele frequencies within a population
Mutation	Random heritable change in DNA sequence; source of new alleles
Natural selection	Differential reproduction based on heritable traits
Panmixia	Random mating within a population
Reducing atmosphere	Atmosphere lacking free O2; early Earth condition
Reproductive isolation	Inability of two populations to interbreed and produce fertile offspring
Speciation	Formation of new species through accumulated genetic divergence
Stabilizing selection	Selection favouring intermediate phenotypes; reduces variation
Sympatric speciation	Speciation without geographic isolation
Vestigial organ	Reduced, non-functional remnant of an ancestral functional structure