Final answer:
The bottleneck effect occurs when a natural disaster significantly reduces a population's size, resulting in a loss of genetic diversity and potential vulnerability due to the random sampling of surviving alleles.
Step-by-step explanation:
The bottleneck effect is a phenomenon in population genetics where a natural disaster drastically reduces the size of a population, resulting in a significant loss of genetic diversity. As a situation of the bottleneck effect, consider a wildfire sweeping through a forest, indiscriminately killing a large majority of a particular species within that habitat. The few surviving individuals will carry their alleles forward, which by chance may not be representative of the original population's genetic diversity. Consequently, the post-disaster population will have reduced genetic variation and potentially limited adaptability to future environmental changes or pressures.
This sudden decline in population size and the subsequent random sampling of alleles can lead to changes in allele frequencies, and therefore, the genetic structure of the population might change drastically. The new gene pool may consist of alleles that confer neither an advantage nor disadvantage or may be less optimal for survival compared to the pre-disaster gene pool. Thus, the bottleneck effect can result in a population that is less genetically diverse and possibly more vulnerable to other threats, such as disease or further habitat loss. Over time, this can impact the population's ability to survive and adapt to the ever-changing environment.