Which is not related to S-shaped population curve?

Options

A. Environmental resistance suddenly becomes effective
B. Exponential phase is followed by decline phase
C. Mass mortality and population crash occurs
D. a and c

Answer

To determine which option is not related to the S-shaped population curve, we need to understand the characteristics of the S-shaped curve, also known as the logistic growth curve. Here’s a step-by-step breakdown of the solution:

### Step 1: Understand the S-shaped (Logistic) Population Curve
The S-shaped curve represents how a population grows over time. It consists of different phases:
- **Lag Phase (Accelerating Phase)**: Initial slow growth as the population starts to increase.
- **Exponential Phase (Log Phase)**: Rapid growth as resources are abundant.
- **Stationary Phase**: Growth slows down as the population reaches carrying capacity, where birth rates equal death rates.

### Step 2: Analyze Each Option
We need to analyze the options provided to identify which one does not relate to the S-shaped curve.

1. **Environment resistance suddenly becomes effective**: This statement suggests that environmental resistance (factors that limit population growth) suddenly has an impact, which does not align with the gradual transition seen in the S-shaped curve.

2. **Exponential phase is followed by decline phase**: This statement is correct. After the exponential phase, the population does not immediately decline but enters the stationary phase where growth stabilizes.

3. **Mass mortality and population crash occurs**: This statement implies a sudden decline in population, which is not a characteristic of the S-shaped curve. The curve shows a gradual stabilization rather than a crash.

4. **A and C are correct**: This option suggests that both options 1 and 3 are not related to the S-shaped curve.

### Step 3: Conclusion
Based on the analysis, options 1 and 3 are not related to the S-shaped population curve. Therefore, the correct answer is that both options A (Environment resistance suddenly becomes effective) and C (Mass mortality and population crash occurs) are not related to the S-shaped curve.

### Final Answer
Options A and C are not related to the S-shaped population curve.

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