After exponential increase, population becomes stagnant. The growth curve is

Options

A. circular
B. fluctuating
C. J-shaped
D. S-shaped

Answer

To determine the shape of the growth curve after an exponential increase in population followed by stagnation, we can analyze the phases of population growth and their graphical representation.

### Step-by-Step Solution:

1. **Understanding Population Growth Phases**:
- Initially, when a population is introduced to a new environment, it goes through several phases: lag phase, log (exponential) phase, and declining phase.
- The lag phase is when individuals are maturing and there is little to no increase in population size.
- The log phase is characterized by rapid population growth due to abundant resources.
- Eventually, the population growth slows down as resources become limited, leading to the declining phase.

2. **Carrying Capacity**:
- The population will eventually reach a point known as the carrying capacity (denoted as K), where the environment can no longer support further growth.
- At this stage, the population size stabilizes, indicating stagnation.

3. **Graphical Representation**:
- The growth curve can be plotted on a graph where the y-axis represents population density and the x-axis represents time.
- The curve starts with a lag phase, followed by a steep increase during the log phase, and then levels off as it approaches the carrying capacity.

4. **Identifying the Shape of the Curve**:
- The overall shape of this growth curve is typically S-shaped (sigmoidal). It starts slowly, increases rapidly, and then levels off as it reaches the carrying capacity.
- This S-shape reflects the initial lag, rapid growth, and eventual stabilization of the population.

5. **Conclusion**:
- Therefore, after an exponential increase, when the population becomes stagnant, the growth curve is S-shaped.

### Final Answer:
The growth curve after exponential increase, when the population becomes stagnant, is S-shaped.