Primary succession on rocks starts with

Options

A. herbs
B. animals
C. lichens
D. trees

Answer

### Step-by-Step Text Solution

1. **Understanding Primary Succession**: Primary succession refers to the process of ecological change that occurs in an area where no soil exists, such as bare rocks. This process begins with the colonization of pioneer species.

2. **Identifying the Starting Point**: In the case of primary succession on rocks, the initial substrate is bare rock. The first organisms to colonize this environment are crucial for the development of soil and the subsequent stages of succession.

3. **Role of Physical and Chemical Weathering**: Before biological organisms can inhabit the rocks, physical and chemical weathering processes break down the rock into smaller particles. This includes processes like sunlight causing expansion and contraction, rain, and freezing of water in cracks.

4. **Biological Weathering**: While physical and chemical processes prepare the rock, biological weathering is essential for the establishment of life. This is where organisms like lichens come into play.

5. **Lichens as Pioneer Species**: Lichens, which are symbiotic associations between fungi and algae or cyanobacteria, are the first organisms to colonize bare rocks. They can survive in harsh conditions and begin the process of soil formation by breaking down the rock and contributing organic material as they die and decompose.

6. **Subsequent Stages of Succession**: After lichens establish themselves, they create conditions suitable for other plants. This leads to the growth of small herbs and shrubs, followed by the establishment of small trees, and eventually larger trees, completing the succession process.

7. **Conclusion**: Therefore, the primary succession on rocks starts with lichens, which are the pioneer species that initiate the ecological process.