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Vocabulary flashcards covering evolutionary theory, phylogenetics, and population-genetics concepts for Exam 3.
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Hardy–Weinberg Equilibrium
A theoretical state in which allele and genotype frequencies remain constant from generation to generation in the absence of evolutionary forces; needed to infer heterozygote or homozygote frequencies from allele frequencies.
Natural Selection (Darwin)
Process whereby individuals with heritable traits better suited to their environment survive and reproduce more successfully, driving evolutionary change.
Inheritance of Acquired Characteristics (Lamarck)
Discredited idea that traits gained during an organism’s lifetime can be passed to offspring.
Uniformitarianism (Hutton)
Geologic principle that Earth’s features result from continuous, slow processes occurring over vast time periods.
Neutral Theory of Molecular Evolution
Theory holding that most DNA sequence changes are caused by random genetic drift of neutral mutations rather than by natural selection.
Kimura’s Fixation Rule
Statement that the rate of fixation of neutral mutations equals the mutation rate (μ) and is independent of population size (N).
Adaptive Radiation
Rapid diversification of a single ancestral lineage into many species adapted to different ecological niches.
Monophyletic Group
A clade containing an ancestor and all of its descendants.
Paraphyletic Group
A group containing an ancestor and some, but not all, of its descendants.
Polyphyletic Group
A set of organisms that do not share an immediate common ancestor within the group; members have different evolutionary origins.
Homology
Similarity in structure or genetics resulting from shared ancestry.
Analogy
Similarity in traits due to convergent evolution or similar selective pressures, not common ancestry.
Homologous Trait
A characteristic inherited from a common ancestor that may have diverged in function over time.
Convergent Evolution
Independent evolution of similar traits in distantly related lineages due to similar environmental pressures.
Divergent Evolution
Accumulation of differences between closely related populations, leading to speciation.
Artificial Selection
Human-directed breeding for desired traits in plants or animals.
Directional Selection
Natural selection that favors one extreme phenotype, shifting allele frequencies toward that extreme.
Stabilizing Selection
Selection that favors intermediate phenotypes and reduces variation at the extremes.
Disruptive Selection
Selection that favors both extreme phenotypes over intermediate forms, potentially leading to bimodal traits.
Sexual Selection
Selection for traits that improve mating success rather than survival.
Intersexual Selection
Mate choice where one sex selects mates based on specific traits of the opposite sex (e.g., female choice of male displays).
Intrasexual Selection
Competition among members of the same sex for access to mates (e.g., male–male combat).
Gene Flow
Movement of alleles among populations through migration and breeding, reducing genetic differences between populations.
Genetic Drift
Random changes in allele frequencies in small populations due to chance events.
Bottleneck Effect
Genetic drift resulting from a sharp reduction in population size, causing allele frequencies to differ from the original population.
Founder Effect
Genetic drift that occurs when a small number of individuals colonize a new area, leading to a gene pool different from the source population.
Genetic Polymorphism
Persistence of two or more distinct alleles in a population over time, maintaining genetic diversity.