The internal ears develop from

Options

A. Ectoderm
B. Endoderm
C. Mesoderm
D. Ectoderm and endoderm.

Answer

**Step-by-Step Solution:**

1. **Identify the Question**: The question asks about the origin of the internal ears during development.

2. **Understand the Germ Layers**: There are three primary germ layers in embryonic development: ectoderm, mesoderm, and endoderm. Each layer gives rise to different structures in the body.

3. **Analyze the Options**:
- **A. Ectoderm**: This layer is responsible for developing the nervous system and sensory organs.
- **B. Endoderm**: This layer primarily forms the gastrointestinal tract and associated organs.
- **C. Mesoderm**: This layer develops into structures such as the heart, kidneys, and muscles.
- **D. Ectoderm and Endoderm**: This option suggests a combination of the two layers.

4. **Determine the Correct Layer**: The internal ears are part of the sensory organs, which are derived from the ectoderm. The ectoderm gives rise to the sensory epithelia, which includes the structures of the ear.

5. **Conclusion**: Based on the analysis, the internal ears develop from the ectoderm.

6. **Final Answer**: The correct answer is **A. Ectoderm**.

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