Question

List three factors that set limits to population increase.

Answer 1

Ans.

• An environmental condition or a resource which can restrict an organism's or a population's growth, distribution or density within an ecosystem is called as a limiting factor.
• Such limiting factors can be either physical or biological and can be recognized by a response of enhanced or reduced growth, availability or distribution of population upon their alteration and while other factors critical for life don't show any change.
• Organisms could not fulfill their fundamental niche because of such limiting factors and instead occupy their actual or realized niche.
• Limiting factors can be broadly categorized into following 2 types ;

a). Density dependent - total population size is used to predict the effect of these factors on a population for eg. predation and disease.

b). Density independent factors - these factors do not depend upon the population size to lilmit the growth of a population for eg. earthquakes and tsunamis.

Examples of limiting factors ;

1). Resources ;

• Many of the resources like food, water, light, space... etc are shared by many populations and thus acts as limiting factors.
• Individuals of a population can face the risk of extinction if enough resources are not available to sustain them.
• Within an ecosystem, a limiting resource helps in determining the carrying capacity.
• Carrying capacity is defined as the maximum number of persons in a group or population that can be supported by a habitat without degradation of an environment.
• Thus, for a population size, carrying capacity plays the role of a moderator.

2). Environmental conditions ;

• Environmental conditions can also play the role of limiting factors for a population.
• Temperature and rain (precipitation) are two of the most important examples of environmental conditions acting as a limiting factor.
• Climate and changes in them with seasons affect these two environmental factors.
• The limiting effect of each of these two environmental factors depend upon the living habitats of a population as well as life history traits of every individual species.
• For example, temperature of a habitat is controls by the sunlight which in turn, and it can also affect the process of photosynthesis by affecting photon energy and enzymes.

3). Biotic factors ;

• Examples of biotic factors which acts as limiting factor for a population include predation, herbivory, parasitism and competition between species.
• These biotic limiting factors all are density dependent.
• For example population size of predators and prey act as a limting factor for each other.