Chapter 4, Problem 9A

Summary Introduction

Introduction :

In ecology, population of organisms are effected by a number of factors which may or may not be related to the density of the population. Density-independent factors are referred to as the factors which does not depend on the density of the population but influences the growth rate of the population.

Answer to Problem 9A

Correct answer :

The correct answer is option (A) A severe drought.

Explanation of Solution

Explanation/justification for the correct answer :

Option(A) A severe drought. Density-independent factors are usually physical factors like a severe drought, hurricane, and earthquake and are unrelated to the size of the population. It acts as a limiting factor that affects the population regardless of its density. So, the correct answer is option (A).

Explanation for incorrect answer :

Option (B)An intestinal parasite. Parasites don’t necessarily result in competition for resources but it affects the health, survival and reproduction of the population when population density increases. Hence, an intestinal parasite can be considered as density dependent factor. So, this is an incorrect answer.

Option (C)A fatal virus. Infectious disease-causing organisms reduces the ability of survival and reproduction in individuals of the population. The health is stressed and their likelihood of dying is greater which reduces the population density. The spread of the virus depends on the density of the population.So, this is an incorrect answer.

Option (D)Severe Overcrowding.When the population density increases to a much greater extent, it exerts a negative impact on the population by limiting the resources available to the individuals. With increased number of individuals, intraspecific competition increases which in turn limits the growth of the population. So, this is an incorrect answer.