Final answer:
In secondary succession, a lake filling in and becoming shallower typically turns into a wetland and then eventually into a forest as ecological recovery progresses with nutrient-rich soil already in place.
Step-by-step explanation:
In secondary succession, as a lake fills, it becomes shallower, turning into a wetland and then a forest. Secondary succession refers to the ecological recovery of an area that has been disturbed but where soil still remains. A typical scenario might involve an area where a fire, flood, or human activity has cleared an ecosystem but left the soil intact. With the existing nutrient-rich soil, pioneer species that are well-adapted to the conditions, such as grasses, move in first. Over time, these species are replaced by more complex plant communities, and finally, the area may once again support a mature forest.