Select the Taxon mentioned that represents both marine and fresh water species

Options

A. Cnidaria
B. Echinoderms
C. Ctenophora
D. Cephalochordata

Answer

To solve the question of which taxon represents both marine and freshwater species, we can analyze the given options step by step.

### Step-by-Step Solution:

1. **Understanding the Taxa**: We need to identify the four taxa mentioned in the question. The options provided are:
- Echinodermata
- Ctenophora
- Cephalocordata
- Cnidaria

2. **Analyzing Echinodermata**: Echinoderms are exclusively marine organisms. They are not found in freshwater environments. Therefore, this taxon does not represent both marine and freshwater species.

3. **Analyzing Ctenophora**: Similar to Echinoderms, Ctenophores are also exclusively marine. They do not inhabit freshwater environments. Thus, this taxon also does not represent both types of water.

4. **Analyzing Cephalocordata**: Cephalocordates are primarily marine organisms. They are not known to inhabit freshwater environments. Hence, this taxon does not represent both marine and freshwater species.

5. **Analyzing Cnidaria**: Cnidarians, also known as coelenterates, are mostly marine organisms, but they also include some species that are found in freshwater. Specifically, the class Hydrozoa within Cnidaria contains species that can live in freshwater environments. Therefore, Cnidaria represents both marine and freshwater species.

6. **Conclusion**: Based on the analysis, the taxon that represents both marine and freshwater species is **Cnidaria**.

### Final Answer:
**Cnidaria**

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