Select first group of organisms to colonise rocks and hence, are of great ecological importance.

Options

A. Mosses alonwith horsetials
B. Mosses alongwith lichens
C. Ferns alongwith mosses
D. Mosses alongwith grasses

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the first group of organisms that colonize rocks and are ecologically important. This refers to organisms that can thrive in harsh environments and contribute to ecological processes.

2. **Identifying the Groups**: The options provided include:
- Mosses along with horsetails
- Mosses along with lichens
- Ferns along with mosses
- Mosses along with grasses

3. **Analyzing the Options**:
- **Mosses along with horsetails**: Horsetails are pteridophytes and not the first colonizers.
- **Mosses along with lichens**: Mosses are bryophytes, and lichens are a symbiotic association between algae and fungi. Both are known to colonize bare rocks and are crucial for soil formation.
- **Ferns along with mosses**: Ferns are also pteridophytes and not the first colonizers.
- **Mosses along with grasses**: Grasses are not typically the first colonizers of rocks.

4. **Selecting the Correct Answer**: The correct answer is **mosses along with lichens**. These organisms are the pioneers in ecological succession on bare substrates like rocks. They help in breaking down the rock surface, contributing to soil formation, and providing a habitat for other organisms.

5. **Conclusion**: Therefore, the first group of organisms to colonize rocks and of great ecological importance is **mosses along with lichens**.

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