One significant environmental factor that can influence natural selection and increase genetic diversity is habitat variability. When a species is exposed to diverse habitats with varying conditions, individuals that possess different traits may have different survival and reproductive success depending on those conditions. This variability can lead to natural selection favoring a broader range of traits, thereby increasing genetic diversity within the population.
Example: Darwin's Finches in the Galápagos Islands
A well-known example is the case of Darwin's finches in the Galápagos Islands. These birds have diversified into multiple species, each adapted to their specific ecological niches on different islands. The islands exhibit varied environments, including differences in vegetation, landform, and climate, which create distinct habitats.
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Variability in Food Sources: Finches have adapted to different food sources available in their respective habitats. For example, some finches have developed strong, thick beaks to crack hard seeds, while others have long, thin beaks suited for probing insects in the bark of trees or the ground. This divergence in traits reflects the selective pressures exerted by the differing food resources found in their environments.
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Selection Pressures: These varied habitats lead to different selection pressures. For instance, during drought years, when certain seeds were scarce, finches with beaks better suited for feeding on the remaining types of seeds proliferated, while others with less favorable traits either struggled to survive or produced fewer offspring.
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Increased Genetic Diversity: As each finch population adapted to their specific habitats through natural selection, genetic variation within and between populations increased. This is because traits that were advantageous in a particular environment were selected for, while less favorable traits were pushed out. Over time, this process led to the emergence of multiple finch species, each with unique characteristics.
In summary, the habitat variability across the Galápagos Islands serves as a prime example of how diverse environmental conditions can influence natural selection, leading to the development of a wide range of traits and increasing genetic diversity among Darwin's finches.
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