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KEY CONCEPT Darwin proposed natural selection as a mechanism for evolution.

Darwin proposed natural selection as a mechanism for evolution, driven by key insights like variation, overproduction, adaptation, and descent with modification. This theory explains how evolution occurs through existing variations and adaptations that enhance survival and reproductive success over generations.

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KEY CONCEPT Darwin proposed natural selection as a mechanism for evolution.

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  1. KEY CONCEPT Darwin proposed natural selection as a mechanism for evolution.

  2. neck feathers crop tail feathers Several key insights led to Darwin’s idea for natural selection. • Darwin noticed a lot of variation in domesticated plants and animals. • Artificial selection is the process by which humans select traits through breeding.

  3. Natural selection is a mechanism by which individuals that have inherited beneficial adaptations produce more offspring on average than do other individuals. • Heritability is the ability of a trait to be passed down. • There is a struggle for survival due to overpopulation and limited resources. • Fitness is a measure of the ability to survive and produce more offspring than fellow population members. • Darwin proposed that adaptations arose over many generations.

  4. VARIATION OVERPRODUCTION ADAPTATION DESCENT withMODIFICATION Natural selection explains how evolution can occur. • There are four main principles to the theory of natural selection. • variation • overproduction • adaptation • descent with modification

  5. Variation • The heritable differences that exist in every population are the basis for natural selection.

  6. Overproduction • Having many offspring increases the chances for survival but also may cause competition for resources.

  7. ADAPTATION • A certain variation that allows an individual to survive better than other individuals it competes against.

  8. Descent with modification • Heritability of adaptations. More individuals will have the trait in every following generation as long as environmental conditions remain favorable for that trait.

  9. five digits wrist bone Natural selection acts on existing variation. • Natural selection can act only on traits that already exist. • Structures take on new functions in addition to their original function.

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