Final answer:
Succession is the process by which species in a community appear and disappear over time. Primary succession begins in lifeless areas where soil must be created, involving pioneer species that can withstand harsh conditions, whereas secondary succession occurs in disturbed areas with existing soil, progressing more quickly.
Step-by-step explanation:
Succession describes the sequential appearance and disappearance of species in a community over time. Primary succession and secondary succession are two main modes of succession that differ fundamentally in the conditions they begin in.
Primary Succession
Primary succession occurs on newly exposed or newly formed land that has not been previously colonized by living organisms, such as land created by lava flow from a volcanic eruption. This process begins with the establishment of pioneer species, which are typically hearty plants and lichens that can tolerate the harsh conditions and help in forming soil by breaking down the mineral-rich substrate. Over time, these species contribute to the development of organic material, facilitating the growth of a more diverse set of organisms, leading to an equilibrium state or climax community.
Secondary Succession
Secondary succession, on the other hand, occurs in areas where an ecosystem has been disturbed but where soil and some life forms remain, such as after natural disasters like floods or human activities like agriculture. This process is generally faster than primary succession since the soil already contains nutrients necessary for plant growth. The pioneer species in secondary succession are those that first colonize the previously disturbed soil and are usually different from the pioneer species in primary succession.