A group of small fish live in a lake with a uniformly light-brown sandy bottom. Most of the fish are light brown, but about 10% are mottled. This fish species is often prey for large birds that live on the shore. A construction company dumps a load of gravel in the bottom of the lake, giving it a mottled appearance. Which of these statements presents the most accurate prediction of what will happen to this fish population? 1. The proportion of mottled fish will increase over time.2. In two generations, all the fish will be mottled.3. There is no way to predict the result.4. As the mottled fish are eaten, more will be produced to fill the gap.5. The ratios will not change.

The mottled appearance of the bottom of the lake provided a survival benefit to the mottled skinned fishes. This is because a mottled background allows the mottled fishes to camouflage against it and escape predation . On the other hand light brown fishes will become more distinct and visible to the birds and will be hunted. So, soon the proportion of mottled fish in the lake will rise.