Final answer:
The bottleneck effect is a reduction in genetic diversity caused by a population size reduction often due to a catastrophic event, while the founder effect arises when a new population is started by a small number of individuals from a larger population, leading to different allele frequencies in the new population.
Step-by-step explanation:
Both the bottleneck effect and founder effect alter the genetic make-up of a population, but they occur under different circumstances and have distinct impacts on the population's genetic diversity. The bottleneck effect takes place when a significant portion of a population is suddenly eliminated due to an event such as a natural disaster, leaving a small, random sample to continue on. This can lead to a dramatic change in the population's genetic structure as certain alleles may become underrepresented or lost entirely.
In contrast, the founder effect happens when a few individuals from a larger population migrate to form a new population. The genetic structure of the new group reflects the alleles of the founding members, which may differ significantly from the original population. This could lead to a high frequency of certain alleles, or the introduction of new alleles, if the founders carry unique genetic variations.