The light colored rock pocket mice in New Mexico blend in with the sandy soil of the area, but on darker lava flow, the light co
lor makes them stand out, making them easy prey for owls, hawks, and other visual predators. A gene mutation has produced a darker fur color that makes the some mice better able to survive predators in the lava environment. Over time, the darker colored mice became more common in the area of the lava flow. Why did dark colored rock pocket mice first appear in the population? A)Their environment changed. B)They have a random gene mutation that affects their fur color. C)Individuals within the population had to change color to blend in with the environment D)Predators eat light-colored rock pocket mice, making dark-colored rock pocket mice more likely to survive.
B is the correct answer. The rock pocket mice have a random gene mutation that affects their fur color. The mechanisms of evolution are variation, natural selection, and time. Mutations introduce genetic variability into a population. Natural selection, then, determines which traits are most beneficial. In this case, the selective pressure is the visual predator, making the light colored rock pocket mice the easy source of food while the darker fur color mutation provided camouflage for the darker mice. Over time, if the environment does not change again, the numbers of darker-colored mice will increase within the population, changing the allele frequency for fur color within the pocket mice population.
Mutation is one source of variation (in addition to sex and gene flow). Mutations are rare and occur in a small proportion of individuals. However, due to the advantage that the genetic mutation confers to these individuals, their chances of passing the genes to the next generation is higher than that of the general population.
This way, the allelic frequencies of these advantageous mutated genes increase with each generation and eventually become the majority population over time.
