What best describes ecological succession?

Ecological succession refers to the process by which the structure of a biological community evolves over time. This process involves a series of stages or phases where one community of organisms is gradually replaced by another. The concept emphasizes how ecosystems change and develop, leading to different species compositions in an area over time.

The correct response highlights that ecological succession is characterized by these gradual changes in species composition. In the first stage, often referred to as primary succession, new communities can form on previously uninhabited substrates, such as bare rock or sand. This is followed by more established communities taking over, leading to a mature or climax ecosystem that reflects the changes in species diversity and abundance.

Other concepts mentioned are not accurate descriptions of ecological succession. While competition between species can be present, it is not the defining characteristic of this process. Cyclic patterns of population decline refer more to population dynamics, not the gradual and sequential shift of species seen in succession. Similarly, random genetic variation pertains to genetic changes within species rather than the overall changes in community composition that define ecological succession.