Evolution and Population Genetics

Comprehensive vocabulary flashcards covering evolutionary principles, population genetics, Hardy-Weinberg equilibrium, selection modes, speciation mechanisms, and reproductive barriers.

Evolution

The cumulative genetic change in a population of organisms over time; it is driven by changing environmental conditions rather than an intentional drive toward a "perfect" end goal.

Jean-Baptiste Lamarck's Theory of Evolution

An early evolutionary idea suggesting that life changes via a "use or lose" principle, whereby acquired traits are passed on to offspring based on whether an individual uses or neglects them.

Descent with Modification

Charles Darwin's proposal that all species descended from an ancestral species and accumulated diverse adaptations as descendants spread into varying habitats over time.

Natural Selection

The primary mechanism of evolution wherein environmental pressures favor individuals with specific heritable traits, granting them greater reproductive success and altering allele frequencies across generations.

Evolutionary Fitness

The reproductive success of an individual within its environment, measured specifically by its capability to survive and produce viable, fertile offspring.

Evolutionary Adaptation

A heritable characteristic that enhances an organism's survival and reproduction in a specific environment; it cannot be intentionally developed and acts only on pre-existing genetic variations.

Artificial Selection

The selective breeding of domesticated plants and animals by humans to promote the occurrence of desirable phenotypic traits in future generations.

Sexual Selection

A form of natural selection in which individuals with certain inherited physical characteristics or courtship displays are chosen by the opposite sex, sometimes yielding traits detrimental to survival.

Population

A localized group of interbreeding individuals belonging to the same species; it represents the smallest unit of living matter that can evolve.

Gene Pool

The aggregate of all copies of every type of allele at all loci in every individual in a population at any given time.

Microevolution

A change in the relative frequencies of alleles in a population's gene pool over a succession of generations.

Hardy-Weinberg Principle

The principle stating that the frequencies of alleles and genotypes in a sexually reproducing population remain constant from generation to generation provided that evolutionary influences are absent.

Hardy-Weinberg Equations

The mathematical models $p + q = 1$ (where $p$ is the dominant allele frequency and $q$ is the recessive allele frequency) and $p^2 + 2pq + q^2 = 1$ (representing homozygous dominant, heterozygous, and homozygous recessive genotype frequencies).

Hardy-Weinberg Equilibrium Conditions

The five mandatory criteria required for a population to remain non-evolving: an extremely large population size, no gene flow, no mutations, random mating, and no natural selection.

Genetic Drift

A process in which unpredictable, chance events cause unpredictable fluctuations in allele frequencies from one generation to the next, impacting small populations most significantly.

Bottleneck Effect

Genetic drift resulting from a drastic reduction in population size typically caused by a catastrophic environmental event such as a flood, earthquake, or fire.

Founder Effect

Genetic drift occurring when a few individuals become isolated from a larger original population and establish a new colony whose gene pool composition differs from that of the source population.

Gene Flow

The movement of alleles between populations due to the immigration or emigration of fertile individuals or gametes; it is not a chance event.

Directional Selection

Natural selection that favors individuals at one extreme end of a phenotypic range, shifting a population's frequency curve in that specific direction.

Stabilizing Selection

Natural selection that acts against extreme phenotypes and favors intermediate variants, narrowing the phenotypic variance curve while keeping the mean in place.

Disruptive Selection

Natural selection that favors individuals at both extremes of a phenotypic range over individuals with intermediate phenotypes; also known as diversifying selection.

Coevolution

The reciprocal evolutionary change between two ecologically interdependent species, where each species exerts a selective pressure on the other.

Allopatric Speciation

The formation of new species in populations that are geographically isolated from one another by an extrinsic physical barrier, such as a body of water or mountain range.

Sympatric Speciation

The formation of new species in populations that inhabit the same geographic region, occurring without physical separation through mechanisms like habitat differentiation or polyploidy.

Polyploidy

A chromosomal alteration in which an organism possesses more than two complete sets of chromosomes due to an error in meiosis; a major driver of sympatric speciation in plants.

Adaptive Radiation

A period of rapid evolutionary change in which groups of organisms form many new species whose adaptations allow them to fill distinct ecological niches in a new or changed environment.

Divergent Evolution

An evolutionary pattern wherein two or more related species sharing a common ancestor become increasingly differentiated over time due to differing environmental pressures.

Convergent Evolution

The independent evolution of similar features in evolutionary lineages that do not share a recent common ancestor, occurring as an adaptation to similar ecological niches.

Fossil Record

The historical chronicle of evolution documented by the mineralized remains or imprints of past organisms preserved in rock strata, displaying the chronological sequence of evolutionary appearances.

Biogeography

The scientific study of the geographic distribution of species across geological space and time, offering evidence of common ancestry and evolutionary isolation.

Homologous Structures

Anatomical features present in different species that share a common underlying structural framework because of common ancestry, despite having diverged in function.

Vestigial Structures

Remnants of anatomical features that served important functions in ancestral organisms but have lost their primary original function in modern descendants.

Comparative Embryology

The comparison of early stages of anatomical development across diverse animal species, revealing transient shared structures (such as pharyngeal pouches) that indicate common ancestry.

Molecular Homology

Similarities in genetic codes, DNA sequences, and amino acid sequences of shared proteins (e.g., hemoglobin) that reflect shared evolutionary history among species.

Direct Observation of Evolutionary Change

Empirical evidence of evolution occurring in real time over short spans, such as the rapid development and proliferation of antibiotic resistance in bacterial populations.

Prezygotic Barriers

Reproductive isolation mechanisms that impede mating or prevent fertilization if individuals from different species attempt to mate.

Temporal Isolation

A prezygotic barrier occurring when two species breed during different times of the day, during different seasons, or in different years, preventing gametic exchange.

Behavioral Isolation

A prezygotic reproductive barrier caused by differences in courtship rituals, mating calls, or other species-specific mate-recognition behaviors.

Habitat Isolation

A prezygotic barrier where two species inhabit different environments or ecological niches within the same general area, rarely or never encountering one another.

Mechanical Isolation

A prezygotic barrier where morphological or anatomical differences in male and female sex organs prevent successful copulation or gamete delivery.

Gametic Isolation

A prezygotic reproductive barrier in which copulation or gamete release occurs, but molecular incompatibilities prevent sperm from fertilizing the egg.

Postzygotic Barriers

Reproductive barriers that prevent hybrid zygotes from developing into viable, fertile adults after successful fertilization has taken place.

Hybrid Inviability

A postzygotic barrier where the genes of different parent species interact in ways that impair the hybrid's development or survival, rendering it non-viable or extremely frail.

Hybrid Sterility

A postzygotic reproductive barrier in which hybrid offspring successfully reach adulthood but are completely sterile and unable to produce functional gametes, as seen in mules.

Hybrid Breakdown

A postzygotic barrier in which first-generation hybrids are viable and fertile, but subsequent generations produced by hybrid crosses are feeble or sterile.

Gradualism

An evolutionary model suggesting that species evolve incrementally via the slow, steady, and continuous accumulation of small phenotypic modifications over extensive geological time.

Punctuated Equilibrium

An evolutionary model stating that species remain morphologically stable during long periods of apparent stasis, which are interrupted by brief, episodic bursts of rapid speciation.

Phylogenetic Tree

A diagrammatic representation depicting hypotheses about evolutionary lineages and degrees of relatedness among various biological groups based on shared ancestry.