Final answer:
Population/genetic bottlenecks lead to a significant reduction in genetic diversity, typically caused by natural disasters that result in a small number of survivors who define the genetic structure of the future population.
Step-by-step explanation:
Typically observed in population/genetic bottlenecks is a significant reduction in genetic diversity due to a sudden decrease in population size. This is often caused by natural disasters such as earthquakes or hurricanes that indiscriminately kill a large portion of the population. The bottleneck effect leads to a random sampling of the original group surviving, and consequently, the survivors' genetic structure becomes the new baseline for the entire population. Such events can drastically change the population's genetic makeup, often resulting in reduced genetic variation, which can influence the future evolution and adaptability of the species. Such factors also impact the potential for natural selection, as the available gene pool is much smaller.