Complete question:
Starting on bare rock, what is the usual ecological succession of organisms?
a)shrubs--grasses--lichens--trees
b)lichens--shrubs--grasses--trees
c)grasses--shrubs--lichens--trees
d)liches--grasses--shrubs--trees
Answer:
d)liches--grasses--shrubs--trees
Step-by-step explanation:
The succession is the colonization of an open area and includes all the changes the area suffers since then. It is a sequence of events that involves the establishment of different species through time.
There are two types of succession, primary and secondary, depending on the magnitude of the alteration.
Primary succession refers to an open space with no living organisms, such as a bare rock exposed due to a retreating glacier, a volcanic activity, or an intense fire. If previous species were inhabiting this area, after the event, nothing is left.
In those cases where there is an alteration or disturbance at a site that opens the area, it allows new species to grow. With time, new species arrive and manage to establish again. The order of the establishment depends on the strategies of each of the species to survive.
First, pioneer species arrive. These are the first inhabitants, mostly lichens or moses with the capability of surviving in such an environment. Only a few pioneers can establish in the open space. Pioneers modify the habitat. They make it more suitable for the establishment of later species, converting rock into fertile soil. As conditions get better, new species arrive like grasses. Grasses and pioneers keep modifying the soil, making it better with time. New species arrive, like small species, bushes and shrubs. Habitat modification keeps on going while new species establish (trees, pines, among other big species). They produce shadows, alter the temperature, and humidity, fertilizing the soil, competing for resources. Competition becomes more frequent between species. The first species are eventually eliminated by competition, but new species keep appearing and competing for resources. This sequence continues until the commuting reaches a climax, becoming stable and lasting for hundreds of years until another disturbance occurs.