Biology for IGCSE & O level - Variation And Selection (Section 1 - No. 12)
What is the most likely reason that the tomcod fish developed resistance to PCBs?
The fish adapted by changing their diet.
A mutation arose that protected them from the PCBs.
The PCBs caused the fish to mutate.
The fish learned to avoid the PCBs.
Forklaring
The development of resistance is due to a mutation.