Final answer:
Genetic drift is a random, undirected change in allele frequency that particularly affects small populations. It's part of the evolutionary process and can lead to significant changes in the genetic makeup of a population over time.
Step-by-step explanation:
The term you're looking for is genetic drift. It refers to the random, undirected changes in allele frequency that occur by chance, especially in small populations. Genetic drift can cause significant changes in the genome of a population over time, even without any selective pressure. In small populations, just a few breeding individuals can skew allele frequencies significantly if they produce more offspring purely by chance. Over generations, this can lead to an increase or decrease in certain alleles and ultimately alter the genetic makeup of the population. An example of how genetic drift can affect populations is the founder effect, where a few individuals establish a new population with an allele frequency that differs from the original population.