Final answer:
The replacement of species following a disturbance in an existing community is called secondary succession. It contrasts with primary succession, which occurs on new or lifeless areas.
Step-by-step explanation:
The replacement of species that follows a disturbance in an already existing community is known as secondary succession. This process occurs in areas where an ecosystem has previously supported life but has undergone significant disturbances that did not completely eliminate soil and organic matter. Examples of such disturbances include events like fires, floods, or human activities such as farming that has been abandoned. During secondary succession, certain pioneer species quickly colonize the disturbed area, which is soon followed by a series of other organisms over time. This results in a gradual restoration of the ecological community, often leading to a state similar to its original condition before the disturbance. In contrast, primary succession refers to the colonization and establishment of communities in lifeless areas without soil, such as new volcanic islands or glacial deposits.