Genetic drift occurs when there is no random mating across a population. This causes a change in allelic frequency due to a random sampling of the population.
As the aboriginal population explored the earth, a small part of the population became geographically isolated either due to continental drift and climate changes. As the isolated population grew bigger, they established their own gene pool. This resulted a change in genotypic frequencies from that of the aboriginal population.
False because the third line of defense is specific by identifying the foreign antigen and activating the antibodies that can bind to the invaders and eliminating the spread