Populations in nature can be described based on three important characteristics. These include its *geographic distribution*, *density*, and *growth rate*. *Age structure* can also be a factor.

The geographic distribution, or range, of a population refers to the area that is inhabited by the population. Population density refers to the number of individuals per unit of inhabited area.

Lastly, the growth rate of a population refers to the rate at which the population grows or shrinks depending on certain factors such as the number of births and deaths within the population.

Geographic distribution, density, and growth rate

The size of the population is the number of individuals.

A population’s demographic development is mostly determined by the renewal of its numbers, which is influenced by births, death, international immigration, and, to some extent, interprovincial mobility.

Increased immigration raises the proportion of young adults (15-64 years old), lowers the proportion of children (0-14 years old), and lowers the proportion of the elderly (65 years and older) in the total population.

An exponential growth is an increasing growth rate in which the individuals in a population reproduce at a constant rate due to a great number of resources. It produces a J-shaped curve in the graph. On the other hand, logistic growth occurs when there is a growth decrease once the population reaches its maximum capacity and there are limited resources. It produces the S-shaped growth curve.

Population density generally refers to the number of individuals in a population that inhabits a specific unit of area. The density can vary depending on the species and its ecosystem.

To illustrate, a population of bacteria on a surface may have a high population density since there can be billions of bacterial cells within a small area, such as a few square centimeters.

In contrast, an example of a population with low density would be elephants since there is usually a small number of elephants that occupy a large area such as a few square kilometers.

Under ideal circumstances, a population of species would be able to grow infinitely with enough resources. However, in reality, resources are limited and populations often compete for them.

Since resources are limited, a population of species can only grow up to a certain point. This point is known as the **carrying capacity**, which could be influenced by many different factors.

One factor that could affect the carrying capacity is the amount of resources in a habitat such as food, water, and space. Competition within and between species can also be a factor.

The term carrying capacity is used to tell the maximum number of living organisms that a particular habitat can support. Factors that would affect the carrying capacity of an area are the same factors that limit the population growth. For an instance, the factors which affect the carrying capacity of a forest include competition, predation, parasitism, diseases, extreme climate conditions, natural disasters, and human disturbances.