In the particular order from top to bottom , the answers are;
Gene flow occurs during migration where alleles from one population are introduced to another population hence increasing the population diversity.
Genetic drift occurs when the allelic frequency of a population changes due factors such as calamities and emigration or natural selection.
Natural selection is the force of ‘survival for the fittest’ that is applied differentially on the population by nature.
Correct answers are:
A few beetles move to a new area and establish a new population.
A few beetles enter from a new population.
A predator move in and finds it difficult to prey on the red-colored beetles.