Two species of Amoeba X and Y were kept in fresh water and got adapted. Species X developed contractile vacuole. When both were transferred to sea water and got adapted, both X and Y lost their contractile vacuole. From these observation we conclude that

Options

A. Both X and Y are marine species
B. Species Y is marine and X is fresh water
C. Species X is marine and Y is fresh water
D. Both X and Y are fresh water

Explanation

To solve the question, we need to analyze the observations regarding the two species of Amoeba, X and Y, and their adaptations to different environments.

### Step-by-Step Solution:

1. **Understanding the Environment**:
- Both species of Amoeba X and Y were initially kept in fresh water. Freshwater organisms often have adaptations to deal with the influx of water due to osmosis.

**Hint**: Consider how organisms adapt to their environments, especially regarding water balance.

2. **Adaptation of Species X**:
- Species X developed a contractile vacuole while in fresh water. The contractile vacuole is an organelle that helps expel excess water from the cell, which is crucial for freshwater organisms to maintain osmotic balance.

**Hint**: Think about the role of contractile vacuoles in osmoregulation.

3. **Transfer to Sea Water**:
- When both species were transferred to sea water, they lost their contractile vacuoles. Sea water is hypertonic compared to the internal environment of the amoeba, meaning that water would naturally flow out of the cells.

**Hint**: Reflect on how organisms might adjust their structures when moving from a hypotonic (freshwater) to a hypertonic (seawater) environment.

4. **Conclusion on Adaptation**:
- The loss of contractile vacuoles in both species after being placed in sea water indicates that they no longer needed this adaptation for osmoregulation, as they were now in an environment where they would lose water rather than gain it.

**Hint**: Consider what this implies about the habitat preferences of the two species.

5. **Final Conclusion**:
- From the observations, we conclude that Species X is adapted to freshwater environments (as indicated by the presence of contractile vacuoles), while Species Y may also be a freshwater species that can survive in marine conditions but does not require contractile vacuoles in that environment.

**Hint**: Think about the implications of these adaptations on the classification of the species.

### Final Answer:
Based on the observations, we conclude that Species X is a freshwater species that developed contractile vacuoles for osmoregulation, while Species Y is also adapted to freshwater but can survive in marine conditions without the need for contractile vacuoles. Thus, both species are primarily freshwater species that can adapt to marine environments.