Which of the following statements about secondary succession is true?
a. secondary succession occurs in ecosystems that have no vegetation.
b. secondary succession affects ecosystems that are already established.
c. ecosystems require pioneer species to undergo secondary succession.
d. secondary succession can occur in areas without soil.

The right answer is b. Secondary succession affects ecosystems that are already established.

Ecological succession is the natural process of evolution and development of an ecosystem in a succession of stages: from initial recolonization to a so-called climax stage. Depending on the type of ecological disturbance that led to the formation of a new soil, we can distinguish the primary succession of the secondary succession.

The ecological succession is therefore the theoretical set of stages describing - in time and space - a theoretical and complete evolutionary cycle within a given ecological space. The succession is assessed from the point of view of the ecology of the environment and thus, in a systemic way, in terms of species but also of the structure of occupation of space. This cycle also corresponds to a succession of habitats and living communities (biocenosis).