Describe an environmental factor that could influence natural selection and decrease genetic diversity. Pick a specific example to illustrate your point.

Answer:

One environmental factor that can influence natural selection and decrease genetic diversity is a severe, prolonged drought. This environmental change acts as a selective pressure, favoring individuals with specific traits that allow them to survive in arid conditions—such as plants with extremely deep root systems or animals with high water-retention capabilities. Individuals that lack these specific adaptations are less likely to survive and reproduce. As a result, the alleles responsible for the less-favorable traits are removed from the population's gene pool, which narrows the overall genetic variation. A specific example occurred with Darwin's finches on the island of Daphne Major; during a severe drought, finches with smaller beaks were unable to crack the large, hard seeds that were the only remaining food source. This led to a significant decrease in the population of small-beaked finches, reducing the genetic diversity of beak sizes within that population.