Which one is the most abundant micro-organism?

Options

A. Bacteria
B. Protozoan
C. Viruses
D. Protists

Answer

**Step-by-Step Solution:**

1. **Understanding Micro-organisms**: Micro-organisms include various types of organisms such as bacteria, protozoa, viruses, and protists. Each of these groups has distinct characteristics and habitats.

2. **Bacteria**: Bacteria are single-celled organisms that have a cell wall. They are known for their ability to thrive in a wide range of environments, including extreme conditions. This adaptability allows them to inhabit diverse ecosystems.

3. **Habitat of Bacteria**: Bacteria can be found in almost every habitat on Earth, from soil and water to extreme environments like hot springs and deep-sea vents. Their presence in such varied habitats contributes to their abundance.

4. **Comparison with Other Micro-organisms**:
- **Protozoa**: These are also single-celled but do not have cell walls. They are found in more specific and limited habitats compared to bacteria.
- **Viruses**: Viruses are non-cellular and require a host to replicate. They do not exist independently in the environment like bacteria do.
- **Protists**: Protists are eukaryotic and mostly unicellular but are also limited in their habitats due to the absence of cell walls.

5. **Conclusion**: Given the ability of bacteria to survive in a wide range of environments and their presence in almost all habitats, it is clear that bacteria are the most abundant micro-organisms on Earth.

**Final Answer**: The most abundant micro-organism is **bacteria**.

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