Lichens are composed of two organisms, a fungus
that cannot make its own food and algae that contain
chlorophyll. Lichens may live on the bark of trees or
even on bare rock. They secrete acids that tend to
break up the rock they live on, helping to produce
soil. As soil accumulates from the broken rock and
dead lichens, other organisms, such as plants, may
begin to grow.
3. The ability of lichens to alter their environment,
enabling other organisms to grow and take their
places in that environment, is one step in the process
of
A) biological evolution
B) ecological succession
C) maintenance of cellular communication
D) differentiation in complex organisms

B) ecological succession

Explanation:

The analogy given in this question describes ECOLOGICAL SUCCESSION, which is the series of changes that an ecosystem undergoes over a period of time. Ecological succession is of two types viz: Primary succession and Secondary succession.

Primary succession involves the series of changes that occurs on a new habitat that has never been previously colonized. This is the case of the colonization of bare rocks with no plant life by LICHENS. The action of the lichen, which involves secretion of acids that disintegrates the rocks into soil, paves way for the colonization of that area by new species.

Lichens, via the role they play in primary succession by helping alter a barren area into a fertile one that accommodates other organisms, makes them be regarded as PIONEERS of primary succession.