Mechanisms of Evolution

Reindeer from a rancher in Alaska escape from their pen during an enormous snow storm. After their escape, they mate with wild caribou that are migrating across the land. The offspring of these have traits for short legs and have tame behavior.

• Gene Flow

• Genetic Drift

• Non-Random Mating

• Natural Selection

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Males of the bighorn sheep species fight one another to show females who is the dominant male and are more likely to mate with females.

• Natural Selection

• Mutation

• Genetic Drift

• Non-Random Mating

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During a hurricane, a population of beetles almost gets completely wiped out. The only beetles that survived were lucky that they were in their nest at the time of the hurricane and had enough food to survive.

• Natural selection

• Genetic Drift

• Gene Flow

• Non-Random Mating

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Insects become resistant to pesticides very quickly, sometime in one generation. If an insect is resistant to the chemical, most of the offspring will also be resistant. Considering that insect generations can be a matter of weeks, insects in an area can become immune to a chemical within months.

• Mutation

• Natural Selection

• Genetic Drift

• Gene Flow

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A chemical spill causes a genetic change in the offspring of ladybugs to have blue dots instead of black dots.

• Natural Selection

• Genetic Drift

• Mutation

• Gene Flow

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A certain type of plant can produce blue or yellow flowers. During a fire, many yellow flowers are destroyed and now since blue is the dominant trait, the plant reproduces offspring that produce only blue flowers.

• Non-Random Mating

• Gene Flow

• Mutation

• Genetic Drift

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This is the pattern of natural selection where BOTH of the extreme versions of a trait are more advantageous than the average, so a population evolves in both directions away from the average

• Directional Selection

• Disruptive Selection

• Stabilizing Selection

• Radical Selection

This is one of the mechanisms of evolution; it is a continuous process in which organisms with traits that make them better-adapted to their environment are more likely to survive and reproduce than organisms without such adaptations

• Directional selection

• Microevolution

• Gene flow / genetic drift

• Natural selection

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This is a pattern of natural selection where one extreme form of a trait is more advantageous than the average or the opposite extreme; as a result, this trait in the population tends to evolve towards that one extreme

• Directional selection

• Disruptive selection

• Stabilizing selection

• Forward selection

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This is the process that ultimately creates new variations and changes in DNA; leads to the creation of new alleles

• Mutation

• Microevolution

• Natural selection

• Gene flow / genetic drift

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