Which of the following is not living fossil?

Options

A. Cycas
B. Metasequoia
C. Gnetum biloba
D. Wetwitschia

Answer

To determine which of the following is not a living fossil, we need to first understand what a living fossil is. A living fossil is an organism whose physical form has remained relatively unchanged over millions of years, indicating that it has not undergone significant evolutionary changes.

### Step-by-Step Solution:

1. **Define Living Fossil**:
- A living fossil is an organism that has remained unchanged for millions of years, showing little to no evolution.

2. **Evaluate the Options**:
- **Cycus**: This plant has not undergone significant changes over millions of years and is considered a living fossil.
- **Metasequoia**: This gymnosperm has also remained largely unchanged and is recognized as a living fossil.
- **Ginkgo biloba**: This plant has shown very little evolutionary change over millions of years and is classified as a living fossil.
- **Welwitschia**: This plant has undergone significant evolutionary changes to adapt to desert conditions, including changes in its photosynthesis process.

3. **Identify the Non-Living Fossil**:
- Among the options, Welwitschia is the only one that has experienced significant evolutionary changes, making it not a living fossil.

4. **Conclusion**:
- Therefore, the answer to the question "Which of the following is not a living fossil?" is **Welwitschia**.