Genetic drift - Geneticdrift . .For example,,

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Genetic drift Another mechanism for evolution is genetic drift.  Genetic drift  occurs when a small group of  individuals leaves a population and establishes a new one in a geographically isolated region. For  example, when a small population of fish is placed in a lake, the fish population will evolve into one  that is different from the original. Fitness of a population is not considered in genetic drift, nor does  genetic drift occur in a very large population.  Natural selection Clearly, the most important influence on evolution is natural selection, which occurs when an  organism is subject to its environment. The fittest survive and contribute their genes to their  offspring, producing a population that is better adapted to the environment. The genes of less-fit  individuals are eventually lost. The important selective force in natural selection is the environment.
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