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the change in a population's inherited traits from generation to generation

natural selection

the evolutionary process by which favorable traits that are heritable become more common in successive generations

evolutionary adaptations

inherited traits further developed through evolution


the slow, gradual steps of change


the philosophy of science that believes that the natural processes operating now are doing so at the same rate as in the past

artificial selection

the intentional breeding of certain characteristics over others


any similarity between structures due to shared ancestry

homologous structures

any structures that are sismilar due to shared ancestry

vestigial organs

anatomical structures of organisms in a species which have lost much or all of their original function due to evolution


the study of evolutionary relatedness among various groups of organisms


the collection of people or organisms of a particular species living in a given geographic area or space


one of the basic units of biological classification

Hardy-Weinberg Theorum

a relationship between the frequencies of alleles and the genotype of a population

Hardy-Weinberg equilibrium

when alleles are in perfect Hardy-Weinberg proportion

Hardy-Weinberg equation



evolution that occurs at or above the species level

bottleneck effect

an evolutionary event in which a significant percentage of a population or species is killed or otherwise prevented from reproducing

founder effect

establishing a population by a small number of individuals, carrying only a small fraction of the original population's genetic variation

gene flow

the transfer of gene alleles from one population to another

balanced polymorphism

natural selection maintaining polymorphisms in a population

heterozygote advantage

when heterozygotes have greater fitness than homozygotes

hybrid vigour

the increased strength of various characteristics in hybrids

stabilizing selection

a type of natural selection in which genetic diversity decreases as the population stabilises on a particular trait value

directional selection

when natural selection favors a single allele and therefore, allele frequency continuously shifts in one direction

diversifying (disruptive) selection

a type of evolution that simultaneously favors at both extremes of the distribution

sexual dimorphism

the systematic difference inbetween individuals of different sexes in the same species


the occurrence of small-scale changes in allele frequencies in a population over a few generations


the evolutionary process by which new biological species arise

phyletic evolution

genetic changes that occur within an evolutionary line

branching evolution

when a species evolves separately from itself to form separate groups

prezygotic barriers

barriers that prevent mating between species/prevention of egg fertilisation

morphical species concept

when species are classified as the same species based on anatomy

recognition species concept

a concept that defines a species as a set of organisms that recognise each other as potential mates

cohesion species concept

defines a species as a group of organisms that can exchange genetically

ecological species concept

defines a species as a set of organisms that are adapted to a particular set of resources

evolutionary species concept

a species is a lineage evolving separately from others and with its own unitary evolutionary role and tendencies

allopatric speciation

when populations physically separated by an extrinsic barrier evolve so that if the barrier breaks down, they can't breed

adaptive radiation

rapid speciation of a single or a few species to fill many ecological niches

sympatric speciation

different species sharing the same territory

punctuated equilibrium

rare events that cause milestone evoltion branches

convergent evolution

where unclosely related organisms evolve similar traits as a result of having to adapt to similar environments

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