The interaction between two living organisms of different species which is beneficial to both but is not obligatory because they can live without each other is known as

Options

A. Proto-cooperation
B. Mutualism or symbiosis
C. Commensalism
D. Amensalism

Answer

To solve the question regarding the interaction between two living organisms of different species that is beneficial to both but not obligatory, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Types of Interactions**:
- There are various types of interactions between organisms, such as mutualism, commensalism, and parasitism. It's essential to identify the characteristics of each interaction.

2. **Define Mutualism**:
- Mutualism is an interaction where both species benefit from each other, but it is often obligatory, meaning they rely on each other for survival.

3. **Define Commensalism**:
- In commensalism, one organism benefits while the other is neither helped nor harmed. This does not fit our criteria since both organisms must benefit.

4. **Define Amensalism**:
- Amensalism occurs when one organism is harmed while the other remains unaffected. This also does not meet our criteria.

5. **Identify Proto-cooperation**:
- Proto-cooperation is a type of interaction where both species benefit from each other, but it is not obligatory. This means that both organisms can survive independently without the interaction.

6. **Conclusion**:
- Based on the definitions and characteristics of the interactions, the correct answer to the question is **proto-cooperation**.

### Final Answer:
The interaction between two living organisms of different species which is beneficial to both but is not obligatory is known as **proto-cooperation**.

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