Final answer:
Flounder matching the color of the ocean floor is considered an adaptation, a natural selection process enhancing survival by enabling camouflage. In the context of the example given, pollution could impede color-based mate recognition, possibly leading to interbreeding and a reversal of sympatric speciation.
Step-by-step explanation:
Flounder coloration that matches the sandy bottoms is an example of an adaptation. Adaptation refers to the process by which a species becomes better suited to its environment through changes that enhance its chances of survival and reproduction. In the case of the flounder, its ability to blend in with the sandy ocean floor helps it to avoid predators, as they find it harder to see the fish against a matching background. This camouflaging ability is a form of natural selection where traits that improve survival are more likely to be passed down to future generations.
Considering the examples provided, if pollution in a lake makes it hard for fish to distinguish colors, it could lead to a breakdown of reproductive isolation. Without the ability to identify mates from their own species by color, interbreeding between the two recently diverged species might occur, potentially reversing the effects of the sympatric speciation process. If this continues, it may result in an increase in hybrid individuals within the lake's fish population.