Organisms are present but they do reproduce in the zone of

Options

A. Optimum tolerance
B. Intolerance
C. Stress
D. Beyond upper and lower limit of tolerance.

Answer

To solve the question "Organisms are present but they do not reproduce in the zone of," we need to analyze the options provided in relation to the law of tolerance, which describes how organisms respond to environmental factors.

### Step-by-Step Solution:

1. **Understand the Law of Tolerance**: The law of tolerance, proposed by Shelford in 1911, states that organisms have a range of environmental conditions that they can tolerate. This range is divided into three zones: optimum zone, zone of stress, and zone of intolerance.

2. **Identify the Zones**:
- **Optimum Zone**: In this zone, organisms can survive and reproduce without any limiting factors affecting them. They thrive here.
- **Zone of Stress**: In this zone, organisms can survive but their reproductive activity is reduced. They are present but may not reproduce effectively.
- **Zone of Intolerance**: In this zone, the limiting factors are too extreme, and organisms cannot survive or reproduce at all.

3. **Analyze the Options**:
- **Optimum Tolerance**: This is incorrect because it refers to the zone where organisms can thrive and reproduce.
- **Intolerance**: This is also incorrect as it refers to a zone where organisms cannot survive or reproduce.
- **Stress**: This is the correct option because organisms are present but their reproduction is reduced.
- **Beyond Upper and Lower Limit of Tolerance**: This is incorrect because it implies conditions that are extreme and not conducive to survival or reproduction.

4. **Conclusion**: Based on the analysis, the correct answer is the **zone of stress**, where organisms are present but do not reproduce effectively.

### Final Answer:
The correct answer is **zone of stress**.

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