Final answer:
The term that describes the situation when a disaster reduces a population to a small handful, resulting in smaller genetic variation among the surviving individuals, is called the bottleneck effect.
Step-by-step explanation:
The term that describes the situation when a disaster reduces a population to a small handful, resulting in smaller genetic variation among the surviving individuals, is called the bottleneck effect.
When a disaster randomly kills a large portion of a population, it reduces the gene pool, causing the surviving individuals to have a genetic makeup that is not representative of the initial population. This leads to a decrease in genetic diversity among the surviving individuals.
For example, if an earthquake wipes out a population of rabbits and only a few survive, the genetic variation in the surviving rabbits will be reduced.