Appearance of DDT-resistant mosquitoes is an instance of

Options

A. parallel evolution
B. convergent evolution
C. current evolution
D. divergent evolution

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about the appearance of DDT-resistant mosquitoes and which type of evolution this represents.

2. **Defining DDT**: DDT stands for dichlorodiphenyltrichloroethane, which is a non-biodegradable pesticide that was widely used in agriculture.

3. **Impact of DDT**: After the application of DDT over time, some mosquito populations developed resistance to it, meaning they were no longer affected by the pesticide.

4. **Concept of Evolution**: Evolution refers to the changes that occur over time in species, allowing them to adapt better to their environment for survival.

5. **Types of Evolution**:
- **Parallel Evolution**: This occurs when two species evolve similarly but independently, often in response to similar environmental pressures.
- **Convergent Evolution**: This occurs when unrelated species develop similar traits or functions due to similar environmental challenges, despite having different evolutionary backgrounds.
- **Current Evolution**: This refers to the ongoing adaptations of species to their current environment, which is relevant in the context of DDT resistance.
- **Divergent Evolution**: This occurs when two or more species that share a common ancestor evolve different traits or functions over time.

6. **Analyzing the Case of DDT-Resistant Mosquitoes**: The development of resistance in mosquitoes to DDT is a direct response to the environmental pressure exerted by the pesticide. This adaptation is an example of current evolution, as the mosquitoes are adapting to survive in an environment where DDT is present.

7. **Conclusion**: Therefore, the appearance of DDT-resistant mosquitoes is an instance of current evolution.

### Final Answer:
The appearance of DDT-resistant mosquitoes is an instance of **current evolution**.

---