Correct option is D
The correct answer is option (4): Facilitation, tolerance, and inhibition.
Explanation:
Ecological succession is the process through which an ecosystem changes over time, progressing from one community to another in a somewhat predictable sequence. The mechanisms that drive ecological succession are often categorized into three main types:
Facilitation: This occurs when early colonizers modify the environment in ways that make it more suitable for subsequent species. For example, pioneer species may alter soil conditions or provide shade, which can make the environment more hospitable for other species to establish themselves.
Tolerance: This mechanism refers to the ability of certain species to tolerate the environmental conditions that may be less favorable for other species. As the ecosystem matures, species that are more tolerant of those conditions may replace earlier species.
Inhibition: This occurs when early species actively prevent the establishment or growth of other species. This can happen through competition for resources, allelopathy (the release of chemicals that inhibit other species), or physical barriers to the establishment of other plants.
All three mechanisms—facilitation, tolerance, and inhibition—can play significant roles in the process of ecological succession. For example, in primary succession, facilitation often occurs initially, and as the community develops, tolerance and inhibition mechanisms come into play.
Why the other options are incorrect:
Option (1) Only facilitation and tolerance: This option is incomplete because it omits inhibition, which is also an important mechanism in ecological succession.
Option (2) Disturbance and tolerance: While disturbance (such as fire, flooding, or human activities) can affect succession, it is not considered a mechanism that directly drives ecological succession. The mechanisms driving succession are facilitation, tolerance, and inhibition, not disturbance.
Option (3) Only tolerance and inhibition: This option excludes facilitation, which is an important mechanism in the early stages of succession.
