Answer:
Radiation leads to mutations that causes genetic drift and decrease fitness.
Step-by-step explanation:
Radiation is responsible for changing or altering the DNA sequence within a cell.
Radiation either causes mutation or it leads to cell death.
Most of the ionizing radiation causes mutation within the deep inside of our cells which eventually leads genetic drift which means change in the frequency of the allele in a population over time.
Beneficial mutation confer advantage to the organism. But in this case, the mutation is not beneficial and decreases the fitness of the rodent organisms.