Question

Why might genetic drift occur if a small number of individuals colonize a new habitat?

Answer 1

Genetic drift will occur if small population of individual colonize a new habitat because of reduction of gene pool of a population

Explanation:

Since genetic drift is a change of allelic frequency that occur by chance alone as a result of rondom sampling error from one generation to another. Small number if individuals that tend to colonize a new habitat are more susceptible to random sampling error.
Also small number of individual which act as a source of a new population result a small gene pool of the population