Adapative measure to protect against extreme heat by poikilotherms is

Options

A. Hibernation
B. Sweating
C. Aestivation
D. Chilling

Answer

To answer the question regarding the adaptive measure to protect against extreme heat by poikilotherms, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Poikilotherms**:
- Poikilotherms are organisms whose body temperature varies with the temperature of their environment. This includes many reptiles, amphibians, and fish.

2. **Identifying the Problem**:
- The question asks for an adaptive measure that poikilotherms use to cope with extreme heat.

3. **Exploring the Options**:
- Option A: Hibernation - This is a state of inactivity used by some animals to survive cold temperatures, not heat.
- Option B: Sweating - This is a mechanism primarily used by endothermic animals (warm-blooded) to cool down.
- Option C: Estivation - This is a state of dormancy or inactivity that occurs in some animals during extreme heat or drought.
- Option D: Chilling - This does not refer to a specific adaptive measure for heat.

4. **Focusing on Estivation**:
- Estivation is specifically a response to high temperatures and low water availability. During estivation, metabolic processes slow down, and the organism becomes inactive, conserving energy and moisture.

5. **Conclusion**:
- The correct answer is **Option C: Estivation**. This is the adaptive measure that poikilotherms use to protect themselves against extreme heat.