Pioneer in a hydrosphere are

Options

A. Diatoms
B. ferns
C. lichens
D. Lemna

Answer

**Step-by-Step Solution:**

1. **Understanding the Term "Pioneer":**
- The term "pioneer" refers to the first organisms that colonize a new or disturbed environment. In ecological terms, pioneers are crucial for initiating the process of ecological succession.

2. **Identifying the Hydrosphere:**
- The hydrosphere encompasses all water bodies on Earth, including oceans, rivers, lakes, and wetlands. It is one of the three main spheres of the Earth, alongside the lithosphere (land) and atmosphere (air).

3. **Analyzing the Options:**
- The question provides four options: diatoms, ferns, lichens, and lemma. We need to determine which of these organisms can be classified as pioneers specifically in aquatic environments.

4. **Evaluating Each Option:**
- **Diatoms:** These are microscopic, photosynthetic algae that thrive in aquatic environments. They have a siliceous (silicon-based) skeleton, making them well-adapted to life in water.
- **Ferns:** While ferns are important in terrestrial ecosystems, they are not typically considered pioneers in aquatic environments.
- **Lichens:** Lichens are symbiotic associations between fungi and algae or cyanobacteria, primarily found on land, and not in water bodies.
- **Lemma:** This term refers to a part of a grass flower and is not an organism that would be classified as a pioneer.

5. **Conclusion:**
- Based on the analysis, diatoms are identified as the pioneers in the hydrosphere due to their ability to colonize aquatic environments and their role in initiating ecological processes in these habitats.

**Final Answer:**
- The pioneers in a hydrosphere are **diatoms**.

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