The animal group, where the adults are degenerated but larvae are well developed, is

Options

A. Agnatha
B. Tunicate
C. Amphibians
D. Cephalochordates

Answer

To solve the question regarding the animal group where the adults are degenerated but the larvae are well developed, we can analyze the given options step by step.

### Step-by-Step Solution:

1. **Understanding the Question**: We need to identify an animal group where the adults are degenerated, meaning they have lost some features or functions compared to their larval stage, which is well developed.

2. **Evaluating the Options**:
- **Agnatha**: This group includes jawless fish like lampreys. Both the adult and larval stages possess a sucking mouth, indicating that they are not degenerated. Therefore, this option is incorrect.

- **Tunicate**: Tunicates, also known as sea squirts, undergo a process called retrogressive metamorphosis. In this group, the larval stage is well developed and free-living, while the adult stage is sessile and degenerated. This matches the criteria of the question, making this option correct.

- **Amphibians**: Amphibians undergo metamorphosis, where the larval stage (like tadpoles) develops into a fully formed adult. Both stages are well developed; hence, this option is incorrect.

- **Cephalocordates**: This group includes animals like lancelets. They have a well-developed adult stage and do not show degeneration in adults compared to larvae. Thus, this option is also incorrect.

3. **Conclusion**: The correct answer is **Tunicate**, as it is the only group where the adults are degenerated while the larvae are well developed.

### Final Answer:
The animal group where the adults are degenerated but larvae are well developed is **Tunicate**.