find the odd one w.r.t germ layers which form the following structures?

Options

A. Gonads
B. Adrenal cortex
C. kidneys
D. Iris muscle

Answer

To solve the question of finding the odd one out with respect to germ layers that form the given structures, we will analyze each option based on their origin from the three primary germ layers: ectoderm, mesoderm, and endoderm.

### Step-by-Step Solution:

1. **Understand Germ Layers**:
- The three primary germ layers are:
- Ectoderm: the outermost layer, which gives rise to structures such as skin and nervous system.
- Mesoderm: the middle layer, which forms muscles, bones, and some organs.
- Endoderm: the innermost layer, which develops into the lining of the digestive tract and some organs.

2. **Analyze Each Option**:
- **Gonads**:
- Gonads (testes and ovaries) develop from the mesoderm.
- **Adrenal Cortex**:
- The adrenal cortex, part of the adrenal glands, also arises from the mesoderm.
- **Kidneys**:
- Kidneys develop from the mesoderm as well.
- **Iris Muscles**:
- Iris muscles, which control the size of the pupil, arise from the ectoderm.

3. **Identify the Odd One Out**:
- From the analysis:
- Gonads, adrenal cortex, and kidneys all arise from the mesoderm.
- Iris muscles arise from the ectoderm.
- Therefore, the odd one out is the **Iris Muscles**.

4. **Conclusion**:
- The answer to the question is **Iris Muscles** (Option D), as it is the only structure that originates from the ectoderm, while the others originate from the mesoderm.