The ratio of the volume of `CO_(2)` evolved to the volume of `O_(2)` consumed in respiration is called.

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the term that describes the ratio of the volume of carbon dioxide (CO2) evolved to the volume of oxygen (O2) consumed during the process of respiration.

2. **Identifying the Concept**: In respiration, the exchange of gases occurs where CO2 is produced and O2 is consumed. The relationship between these two gases can be quantified.

3. **Defining the Ratio**: The specific ratio of CO2 produced to O2 consumed is known as the **Respiratory Quotient (RQ)**. This ratio helps in understanding the type of substrate being metabolized during respiration.

4. **Explaining the RQ Values**:
- When carbohydrates are used as substrates, the RQ is typically 1, meaning the volume of CO2 evolved equals the volume of O2 consumed.
- When fats are used, the RQ is less than 1, indicating that less CO2 is produced compared to O2 consumed.
- When organic acids (like malic acid) are involved, the RQ can be greater than 1, which often occurs in anaerobic respiration.

5. **Conclusion**: Therefore, the answer to the question is that the ratio of the volume of CO2 evolved to the volume of O2 consumed in respiration is called the **Respiratory Quotient (RQ)** or **Respiratory Ratio**.

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