Which of the following animals is not a pair of poikilotherms?

Options

A. Rana, Trygon
B. Labeo, Pteropus
C. Pristis, Carcharodon
D. Scoliodon, Naja

Answer

To solve the question of which pair of animals is not a pair of poikilotherms, we will analyze each option based on the classification of the animals and their ability to maintain body temperature.

### Step-by-Step Solution:

1. **Understanding Poikilotherms and Homeotherms:**
- Poikilotherms are organisms that cannot maintain a constant body temperature and their body temperature varies with the environment. Examples include amphibians, reptiles, and most fish.
- Homeotherms are organisms that can maintain a constant body temperature regardless of the environment. This includes birds and mammals.

2. **Analyzing the Options:**
- **Option A: Rana and Trigon**
- Rana (frog) belongs to Class Amphibia, which are poikilotherms.
- Trigon (a type of fish) belongs to Class Chondrichthyes (cartilaginous fish), which are also poikilotherms.
- **Conclusion:** Both are poikilotherms.

- **Option B: Labiotheropus and Theropus**
- Labiotheropus (a type of fish) belongs to Class Actinopterygii (ray-finned fish), which are poikilotherms.
- Theropus (a type of mammal) belongs to Class Mammalia, which are homeotherms.
- **Conclusion:** This pair is not a pair of poikilotherms because Theropus is a homeotherm.

- **Option C: Pristis and Carcharodon**
- Pristis (sawfish) and Carcharodon (great white shark) both belong to Class Chondrichthyes.
- **Conclusion:** Both are poikilotherms.

- **Option D: Scoliodon and Naja**
- Scoliodon (dogfish) belongs to Class Chondrichthyes, which are poikilotherms.
- Naja (cobra) belongs to Class Reptilia, which are also poikilotherms.
- **Conclusion:** Both are poikilotherms.

3. **Final Answer:**
- The only pair that does not consist of poikilotherms is **Option B: Labiotheropus and Theropus**. Therefore, the correct answer is **B**.