What is a Process That Begins When a Pioneer Species

Question

What is a process that begins when a pioneer species colonizes a barren habitat with no soil?  
A) Primary succession
B) Species introduction
C) Intermediate disturbance
D) Secondary succession
E) Ecological succession

Accepted Answer

Primary succession is the process that begins when a pioneer species, such as mosses or lichens, colonizes a barren habitat with no soil. Over time, these organisms break down rocks and other materials to form soil, which allows for the establishment of more complex plant species. This process can take hundreds or even thousands of years to reach a climax community.