Bare rock, no organisms – Glacier leaves behind bare rock; Volcano produces
bare rock with no organisms.
Pioneer species begins breaking down rock. Pioneer species: 1st organism to live in an area. Pioneer species, usually lichens, grows on rock. Lichens secrete acids that begin breaking rock into small particles, which mix with lichen remains to begin making soil.
More complex plants, usually mosses, begin growing when soil is deep enough, after many years; eventually replace (succeed) lichens.
Tiny organisms such as insects move in, add their remains to soil.
Larger, more complex plants: As soil gets thicker ferns succeed mosses.
Grasses and wildflowers may succeed ferns.
When enough soil has developed, shrubs and small trees move into the area.
Forests: Soil may be deep enough after hundreds or thousands of years for
pine or hardwood forests.