Parasites show

Options

A. progressive evolution
B. speciation
C. retrogressive evolution
D. coevolution

Answer

### Step-by-Step Solution

1. **Understanding the Options**: The question asks about the nature of evolution exhibited by parasites. The options provided are:
- Progressive evolution
- Speciation
- Retrogressive evolution
- Co-evolution

2. **Defining Each Term**:
- **Progressive Evolution**: This refers to the evolution of organisms towards more complex forms or adaptations, often in response to environmental pressures.
- **Speciation**: This is the process through which new species arise from existing species due to evolutionary changes.
- **Retrogressive Evolution**: This describes a process where complex organisms evolve into simpler forms, which may or may not be advantageous.
- **Co-evolution**: This is the process where two or more species influence each other's evolution, often seen in predator-prey or parasite-host relationships.

3. **Analyzing Parasites**: Parasites, such as tapeworms, rely on their hosts for survival. They adapt to the changes in their host's biology to continue their existence. This relationship requires both the parasite and the host to evolve in response to each other.

4. **Identifying the Correct Answer**: Given that parasites must adapt to the changes in their host organisms to survive, the most appropriate term that describes this relationship is **co-evolution**.

5. **Final Answer**: Therefore, the answer to the question "Parasites show" is **co-evolution**.