Final answer:
The first plant community that forms on bare rock often includes pioneer species such as lichen, a symbiotic organism composed of a fungus and algae or cyanobacteria, which plays a key role in soil formation and sets the stage for further ecological succession.
Step-by-step explanation:
The first plant community that forms on bare rock often includes organisms such as pioneer species. A primary example of a pioneer species is lichen, which can survive on bare rocks in harsh conditions due to their unique composite nature. Lichens are symbiotic associations between a fungus and a photosynthetic partner, such as algae or cyanobacteria. This partnership allows the lichen to photosynthesize for energy, while the fungus provides structure and absorbs minerals and nutrients from the rock, aiding in the process of soil formation. As more organic matter is added to the soil by the growth and death of these organisms, the conditions become more suitable for other plants like grasses, shrubs, and eventually trees.
Mosses and liverworts, which do not require roots and can disperse their spores widely, may also play a similar role in primary succession. As the ecosystem develops, these pioneer species lay the foundation for more complex communities, leading to a diverse and stable ecosystem over time.