Final answer:
The mice population experienced a bottleneck effect due to a virus, leading to a sudden and significant reduction in its size, which could affect future genetic diversity and population resilience.
Step-by-step explanation:
The population of mice has undergone a significant decrease in size due to an event known as the bottleneck effect. This is a type of genetic drift caused by external factors, like a virus, leading to a sudden reduction in population size and potential changes in the genetic structure of the population that survives. This effect happens irrespective of the organisms' traits and is usually due to external events like natural disasters or disease outbreaks.
In this specific scenario, the mice population is halved by a virus, which mimics the bottleneck effect by drastically reducing the number of individuals and potentially affecting the genetic diversity of the population. Such events can have long-term effects on the surviving population's genetic makeup and might lead to increased susceptibility to future environmental changes or diseases due to decreased genetic variation.