middle ear and tympanum are absent is

Options

A. anura
B. apoda
C. urodela
D. both B and C

Answer

To determine which group of amphibians lacks the middle ear and tympanum, we can analyze the different orders of amphibians mentioned in the question: Anura, Apoda, and Urodela.

### Step-by-Step Solution:

1. **Identify the Orders of Amphibians**:
- The question mentions three orders: Anura, Apoda, and Urodela.
- Anura includes frogs and toads, Apoda includes caecilians, and Urodela includes salamanders.

2. **Analyze the Order Anura**:
- Anura is known for having a well-developed middle ear and tympanum (the eardrum), which are important for hearing.
- Since Anura possesses these structures, it can be ruled out as the correct answer.

3. **Analyze the Order Apoda**:
- Apoda, also known as caecilians, are limbless and serpentine in shape.
- They do not have a middle ear or tympanum, making this order a potential candidate for the answer.

4. **Analyze the Order Urodela**:
- Urodela includes salamanders, which typically have a middle ear and tympanum.
- Therefore, Urodela can also be ruled out as it does not fit the criteria of lacking these structures.

5. **Conclusion**:
- Since Anura has a middle ear and tympanum, and Urodela also has these structures, the only order that lacks both the middle ear and tympanum is Apoda (caecilians).
- The correct answer to the question is that the middle ear and tympanum are absent in Apoda.

### Final Answer:
The middle ear and tympanum are absent in **Apoda**.