55. Which graph best explains the population growing under saturated conditions of resources?

Introduction

Understanding how populations grow under different environmental conditions is crucial in ecology, resource management, and sustainability planning. One of the most important scenarios is when resources are saturated—meaning they are limited and cannot indefinitely support unchecked population growth. In this context, identifying the correct graphical representation of population growth is essential for students, researchers, and policymakers.

What Does “Saturated Resources” Mean?

Saturated resource conditions occur when the environment can no longer provide unlimited food, space, or other necessities. As a population increases, competition intensifies, and growth slows until the population stabilizes at a certain maximum—the carrying capacity (K).

The S-Shaped (Sigmoid) Curve: The Best Graphical Representation

When resources are saturated, the population growth curve that best explains this scenario is the S-shaped (sigmoid) curve, also known as the logistic growth curve.

Key Features of the S-Shaped Curve

• Lag Phase: Slow initial growth as the population acclimates to the environment.

• Exponential Phase: Rapid increase in population while resources are still relatively abundant.

• Deceleration Phase: Growth rate slows as resources become limited and competition increases.

• Stationary Phase: The population size levels off at the carrying capacity, where birth and death rates balance each other.

This pattern reflects the reality that no environment can support infinite growth due to resource limitations.

Why Not the J-Shaped Curve?

The J-shaped curve represents exponential growth, where resources are unlimited and the population grows without restraint. This scenario is rare in nature and unsustainable in the long term. Under saturated conditions, populations do not continue to grow exponentially; instead, they encounter environmental resistance, leading to the S-shaped curve.

The Logistic Growth Equation

The logistic growth model is mathematically described by:

dNdt=rN(1−NK)dtdN=rN(1−KN)

• N = population size

• r = intrinsic rate of increase

• K = carrying capacity

As N approaches K, the growth rate (dNdtdtdN) decreases and eventually stabilizes.

Real-World Examples

• Wildlife Populations: Deer, fish, and bird populations often grow rapidly when introduced to a new area but stabilize as food and space become limiting.

• Human Populations: In closed systems like isolated islands or biospheres, human populations also follow the S-shaped growth curve as resources become saturated.

Summary Table: Growth Curves

Conclusion

The S-shaped (sigmoid) curve best explains population growth under saturated resource conditions. This curve reflects the reality of limited resources, showing rapid initial growth that slows and stabilizes as the population reaches the environment’s carrying capacity. Recognizing this pattern is vital for effective ecosystem management and sustainable development.