What type of succession occurs on previously uninhabited substrates?

Primary succession occurs on previously uninhabited substrates where no soil exists, such as after a volcanic eruption or when a glacier retreats. This type of succession starts from bare rock or sediment and involves the gradual establishment of a biological community over time.

The process begins with pioneer species, often lichens or certain mosses, which are capable of surviving in harsh conditions and contribute to soil formation as they grow and decompose. As soil develops, it allows for the growth of more complex plants, such as grasses, shrubs, and eventually trees, leading to a more diverse ecosystem.

This concept is distinct from other types of succession. Secondary succession takes place in areas where a disturbance has cleared a biological community but the soil and some organisms remain, such as after a forest fire. Climactic succession refers to a stable community that has reached a point where it remains in balance with the environment, while progressive succession is generally associated with the gradual improvement of ecological conditions over time. These definitions highlight why the correct answer focuses on the absence of soil and life in the initial stages of primary succession.