We see that this is a region near the continents, so it is probable that there is the boundary of a tectonic plates around there. Since there are islands there, it is quite probable that there is a subduction zone near them which means that the oceanic crust is going below the continental one and the continental is slowly elevated. This also shows that the boundary is convergent, since transform boundaries do not lead to elevation. Near convergent boundaries, there are frequently volcanoes and shallow earthquakes. Finally, the climate near Alaska is cold and this does not depend on whether islands are near a boundary or not. So, 2 4 and 5 are correct.
If a population experiences a form of genetic drift, then their genome/genetic code would change. This then can cause the frequency to follow as well. Best example I can think of right now is moths in the Industrial Revolution: all of the soot released into the air caused the moths to be easily seen by birds that ate them (they were all white). This then caused those that were darker, like dark brown to match its new surroundings, weren't eaten by the birds because they could blend in. This caused the phenotype frequency (and therefore genotype) to change to having dark moths being more common than light. And we still see that today! Most moths are still dark brown.
A limiting factor is a variable of a system that, if subject to a small change, causes a non-negligible change in an output or other measure of the system.
