Which of the following is the example of biological control?,

Options

A. Control of mosquitoes by DDT.
B. Control of opuntia by a predator (moth), a type of insect.
C. Decreasing the carrying capacity of the habitat by poisoning it.
D. rescue effect

Answer

To determine which of the given options is an example of biological control, we need to understand what biological control entails. Biological control refers to the method of controlling pests and diseases using other living organisms. Here’s a step-by-step analysis of the options provided:

### Step-by-Step Solution:

1. **Understanding Biological Control**:
- Biological control involves using living organisms to manage pest populations. This can include predators, parasites, or pathogens that specifically target the pest species.

2. **Evaluating Option 1**:
- **Control of mosquito by DDT**:
- DDT is a chemical pesticide. It is not a living organism. Therefore, this method does not qualify as biological control since it involves using a non-living agent to control a living pest (mosquito).
- **Conclusion**: This option is NOT an example of biological control.

3. **Evaluating Option 2**:
- **Control of opensia by predator moths**:
- Opensia is a living organism (a type of pest), and predator moths are also living organisms. The moths will feed on opensia, effectively reducing its population.
- **Conclusion**: This option IS an example of biological control because it involves controlling a living pest with another living organism.

4. **Evaluating Option 3**:
- **Decreasing the carrying capacity of the habitat by poisoning it**:
- Poisoning the habitat involves using chemicals to reduce the population of organisms, which is not a biological method. This is an artificial method and does not involve living organisms controlling other living organisms.
- **Conclusion**: This option is NOT an example of biological control.

5. **Evaluating Option 4**:
- **Rescue effect**:
- The term "rescue effect" generally refers to a phenomenon in ecology where a population can recover due to immigration from surrounding areas. This does not directly relate to biological control methods.
- **Conclusion**: This option is NOT an example of biological control.

### Final Answer:
The correct answer is **Option 2: Control of opensia by predator moths**.

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