Final answer:
Succession describes the sequential appearance and disappearance of species in a community over time. At 150 cm, the changes in bacterial numbers illustrate the process of succession because different species of bacteria respond differently to the changing environment, leading to a sequential change in bacterial populations as the community develops.
Step-by-step explanation:
Succession describes the sequential appearance and disappearance of species in a community over time after a severe disturbance. In secondary succession, a part of an ecosystem is disturbed and remnants of the previous community remain. At 150 cm, the changes in bacterial numbers illustrate the process of succession because different species of bacteria respond differently to the changing environment, leading to a sequential change in bacterial populations as the community develops.