Population and Its Characteristics

Population is the next level in ecological hierarchy the word population has its origin in the Latin word populus meaning 'people'.

In ecology, population is defined as the total number of all individuals of a particular species, which breed among themselves or have the potentiality to do so, in a specific geographical area functioning as a unit of biotic community.

All the populations of different species of a particular geographical area, collectively constitute a biotic community.

Characteristics of Population

Individuals living in the same area are referred as local populations. They all experience similar ecological processess at a particular stage of the life cycle.

Similar populations of a species occupying different geographical areas are called sister populations.

Population is a dynamic unit. Number of individuals may increase or decrease due to many factors due to birth rate, death rate, migration etc. Variation is expressed as population size and population density in a given area at a particular time.

In a geographical area, the population is further divisible into sub-groups called demes. The chances of sexual communication are more between the members of same deme than between the members of different demes. Due to this mating ability, there is free flow of genes in a species.

Population of an area is described on the basis of three parameters:

a) Number and kind of individuals of a species.

b) A given space or an area.

c) Time.

Population size

It is the total number of individuals of a species present in an area at a specific time.

Population density

It is the total number of individuals of a species per unit area or volume at a given time.

(Such as number of animals per square kilometre or number of trees per area etc.)

Population density reflects the success of a species in any given area.

Population density (P.D) can be calculated as,

where N = number of individuals of a species at a specific time.

S = number of unit area in a region /space.

The space is described in two dimensions (such as km², m², cm²) for terrestrial organisms and in three dimensions (such as m³, cm³, ml³) for aquatic organisms and organisms suspended in air.