In dipoblastic animal

Options

A. The cells are arranged in two embryonic layers
B. The cells are arranged in three embryonic layers
C. The cells are arranged in an exteral ectoderm and internal mesoderm
D. The cells are arranged in an external mesoderm and internal endoderm

Answer

### Step-by-Step Solution:

1. **Understanding Diploblastic Animals**:
- Diploblastic animals are characterized by having two embryonic germ layers. These layers are crucial for the development of the organism.

2. **Identifying the Germ Layers**:
- The two germ layers in diploblastic animals are:
- **Ectoderm**: This is the outer layer that forms the skin and nervous system.
- **Endoderm**: This is the inner layer that forms the digestive tract and other internal organs.

3. **Differentiating from Triploblastic Animals**:
- It’s important to note that triploblastic animals have three germ layers: ectoderm, mesoderm, and endoderm. The presence of the mesoderm is what differentiates triploblastic from diploblastic animals.

4. **Examples of Diploblastic Animals**:
- Common examples of diploblastic animals include:
- Cnidarians (e.g., jellyfish, corals, sea anemones).
- Tenophora (e.g., comb jellies).

5. **Analyzing the Options**:
- Now, let’s evaluate the provided options:
- **Option 1**: The cells are arranged in two embryonic layers. (Correct)
- **Option 2**: The cells are arranged in three embryonic layers. (Incorrect)
- **Option 3**: The cells are arranged in an external ectoderm and internal mesoderm. (Incorrect)
- **Option 4**: The cells are arranged in an external mesoderm and internal endoderm. (Incorrect)

6. **Conclusion**:
- The correct answer is **Option 1**: The cells are arranged in two embryonic layers.