How do each of the following processes contribute to evolutionary change?
Trust the guy above. When a single population of a species is split into new groups, it is possible that the different selective pressures inherent in the different geographical locations could cause one portion (or both) of the original population to change. Factors that could differ by location include colors of vegetation and terrain (important if the animal uses camouflage as a defense); different types of terrain (may change claw/foot/talon shape); type of prey or vegetation (important in tooth shape, time of day they hunt, etc); climate (rain, temps, etc). Specific example: geckos on either side of the Sierra Nevadas are different colors, based on the surrounding terrain. B: Genetic drift is the random statistical variation of allele frequency in a gene pool. Natural selection, on the other hand, carefully selects which alleles are more beneficial and increases their frequencies in the gene pool, since those individuals with other alleles die off before reproduction. Genetic drif
