= Solution
<Natural selection> requires variation among individuals, heritable contributions to that variation, and differences in <reproductive success> associated with it. Given those conditions, variant frequencies can change across generations. Competition and finite resources help make <reproductive success> unequal, but selection does not require every interaction to be direct combat. <Mutation> and <Genetic recombination>[recombination] supply variation; they do not generally arise because an organism needs a particular adaptation. Drift also changes frequencies, and common ancestry and branching descent connect population changes to the evolution of species. Selection is a mechanism within evolution, not a synonym for every evolutionary change.<On the Origin of Species by Charles Darwin>[Chapters III–IV, struggle for existence and natural selection]{ref}
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