Degree of fitness
Step-by-step explanation:
In the given condition it is not necessary that the bacterium will retain its high degree of fitness
Fitness mainly depends on the ability of an organism to survive and reproduce and it may not do this as well in a different environment
As given, fittest bacterium was taken from an environment in which the antibiotic amoxicillin is abundant and then placed in an environment in which a different antibiotic is abundant so in this case environment of the bacterium is changed and there is a chance that it will not retain its high degree of fitness