Which of the following pairs of organisms are uricotelic?

Options

A. Cartilaginous fish and mammals
B. Reptiles aned mammals
C. Birds and insects
D. Bony fish and lizards

Explanation

To determine which pairs of organisms are uricotelic, we need to understand what uricotelic organisms are and identify examples of such organisms from the provided options.

### Step-by-Step Solution:

1. **Define Uricotelic Organisms**:
Uricotelic organisms are those that excrete nitrogenous waste primarily in the form of uric acid. This adaptation is beneficial for conserving water, as uric acid is less toxic and can be excreted as a semi-solid paste.

2. **Identify Examples of Uricotelic Organisms**:
Common examples of uricotelic organisms include:
- Reptiles (e.g., lizards, snakes)
- Birds (e.g., sparrows, eagles)
- Insects (e.g., grasshoppers, cockroaches)
- Land snails

3. **Analyze the Given Options**:
The question provides the following pairs of organisms:
- Cartilaginous fish and mammals
- Reptiles and mammals
- Birds and insects
- Bony fish and lizards

4. **Evaluate Each Pair**:
- **Cartilaginous fish and mammals**: These are primarily ureotelic (excrete urea).
- **Reptiles and mammals**: Reptiles are uricotelic, but mammals are ureotelic.
- **Birds and insects**: Both are uricotelic, as they excrete nitrogenous waste in the form of uric acid.
- **Bony fish and lizards**: Bony fish are typically ammonotelic (excrete ammonia), while lizards are uricotelic.

5. **Conclusion**:
The only pair that consists entirely of uricotelic organisms is **birds and insects**.

### Final Answer:
The pair of organisms that are uricotelic is **birds and insects**.