67. Temporary fluctuation in number of individuals aroundthe carrying capacity in most of populations is due to
    (1) density dependent factors
    (2) density independent factors
    (3) Bottle neck phenomenon
    (4) Interspecific competition

Introduction

In nature, populations rarely remain perfectly stable at their environment’s carrying capacity. Instead, they often oscillate—sometimes rising above and sometimes dipping below this ecological limit. Understanding the causes of these temporary fluctuations is crucial for ecologists, wildlife managers, and anyone interested in population dynamics.

What Is Carrying Capacity?

Carrying capacity (K) is the maximum number of individuals an environment can sustainably support over time. It is determined by the availability of resources such as food, water, space, and shelter.

Why Do Populations Fluctuate Around Carrying Capacity?

The Main Cause: Density-Dependent Factors

The primary reason for temporary fluctuations in population size around carrying capacity is the action of density-dependent factors. These are biotic or abiotic factors whose effects intensify as population density increases. Here’s how they work:

• Competition: As population density rises, individuals compete more fiercely for limited resources. This competition can reduce birth rates and increase death rates, causing the population to decline if it overshoots carrying capacity.

• Predation and Disease: Higher densities make it easier for predators and pathogens to find and affect individuals, further regulating population numbers.

• Resource Limitation: When resources become scarce due to high population density, growth slows or reverses, leading to a drop in numbers.

This feedback loop creates a dynamic balance, resulting in populations that fluctuate around, rather than remain fixed at, the carrying capacity.

Other Factors and Why They’re Less Central

• Density-Independent Factors: Events like natural disasters can cause sudden population changes, but these do not specifically cause the regular, temporary fluctuations seen around carrying capacity.

• Bottleneck Phenomenon: This refers to drastic reductions in population size due to random events, not to the typical oscillations around carrying capacity.

• Interspecific Competition: While competition between species can affect carrying capacity, the regular fluctuations around K in a single population are primarily due to density-dependent factors.

Real-World Examples

• Wildlife Populations: Deer, rabbits, and other animals often show cycles of boom and bust as their numbers approach and then temporarily exceed the carrying capacity, only to be brought back down by competition and resource scarcity.

• Microbial Cultures: In laboratory settings, bacteria populations initially grow rapidly but then oscillate around the carrying capacity as nutrients become limiting.

Conclusion

Temporary fluctuation in the number of individuals around the carrying capacity in most populations is due to density-dependent factors. These factors—such as competition, predation, and disease—intensify as populations grow, creating a natural regulatory mechanism that keeps population sizes in check and leads to the characteristic oscillations observed in nature.

Correct answer: (1) Density dependent factors