Cleidoic eggs are characteristic of :

Options

A. Mammals
B. Reptiles and birds
C. Insects
D. Fishes

Answer

To solve the question regarding which group of animals cleidoic eggs are characteristic of, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Definition of Cleidoic Eggs**:
- Cleidoic eggs are eggs that have a protective shell. This shell allows for the exchange of gases while preventing water loss.

2. **Identify the Environment**:
- Cleidoic eggs are laid outside of water, meaning they are adapted for terrestrial (land) environments rather than aquatic ones.

3. **Examine the Characteristics of Cleidoic Eggs**:
- These eggs have a porous shell that can be flexible or hard (calcareous).
- They contain all the necessary nutrients for the developing embryo.

4. **Consider the Options Given**:
- The options provided are: mammals, reptiles and birds, insects, and fishes.

5. **Analyze Each Option**:
- **Mammals**: Most mammals give live birth, except for monotremes (like the platypus) which lay eggs, but these are not cleidoic.
- **Reptiles and Birds**: Both groups lay cleidoic eggs with protective shells that are adapted for life on land.
- **Insects**: While some insects lay eggs, they do not typically have a cleidoic structure.
- **Fishes**: Fish eggs are usually laid in water and do not have a protective shell like cleidoic eggs.

6. **Conclusion**:
- The correct answer is **reptiles and birds**, as they are the groups that lay cleidoic eggs.

### Final Answer:
Cleidoic eggs are characteristic of **reptiles and birds**.

---