How is primary succession different from secondary succession?

Primary succession occurs on newly formed or exposed surfaces, such as bare rock following a volcanic eruption or glacial retreat, where no soil or previous biological community exists. This process begins with the colonization of pioneer species, such as lichens and mosses, which can survive in harsh conditions and begin the soil formation process. Over time, as these organisms die and decompose, they contribute to the development of soil, allowing more complex plants to establish and further facilitate ecosystem development.

In contrast, secondary succession takes place in areas where a disturbance has occurred, such as a forest fire, but the soil and some organisms still remain intact. This allows the succession process to occur more quickly than primary succession since the foundational elements of the ecosystem, like nutrients and seeds, are already present.

Thus, the defining characteristic of primary succession is its initiation on bare, uninhabited surfaces, making option B the correct choice.