A population can be defined as a group of individuals of the same species residing

in a particular geographical area at a particular time and functioning as a unit. For

example, all human beings living at a particular place at a particular time

constitute the population of humans.

The main attributes or characteristics of a population residing in a given area are:

$\to$ Birth rate (Natality): It is the ratio of live births in an area to the population of

an area. It is expressed as the number of individuals added to the population

with respect to the members of the population.

$\to$ Death rate (Mortality): It is the ratio of deaths in an area to the population of

an area. It is expressed as the loss of individuals with respect to the members

of the population.

$\to$ Sex ratio: It is the number of males or females per thousand individuals.

$\to$ Age Distribution: It is the percentage of individuals of different ages in a given

population. At any given time, the population is composed of individuals that

are present in various age groups. The age distribution pattern is commonly

represented through age pyramids.

$\to$ Population density: It is defined as the number of individuals of a population

present per unit area at a given time.