Honors Biology Evolution Practice Exam 2026 – Complete Study Resource

Movement on a fitness landscape happens when allele frequencies in a population change due to evolutionary forces. Natural selection pushes a population uphill toward higher fitness by increasing the frequency of advantageous alleles. Mutation continually introduces new genetic variation, which can create new paths across the landscape or alter which genotypes are most fit. Genetic drift causes random shifts in allele frequencies, especially in small populations, so a population can drift to a different region of the landscape even without a fitness difference. Gene flow brings in alleles from other populations, changing the genetic makeup and allowing movement to new areas of the landscape. Because each force can alter the genetic composition and thus the position on the landscape, all four can move populations.