Final answer:
The process described in the question is called genetic drift and the specific example of genetic drift that occurs when a small group of individuals immigrate to a new area is called the Founder Effect.
Step-by-step explanation:
The process described in the question is called genetic drift.
Genetic drift refers to the change in the frequency of certain traits in a population due to chance events.
The Founder Effect is a specific example of genetic drift that occurs when a small group of individuals immigrate to a new area, leading to a decrease in the risk of extinction and an increase in the population size.