Age structure of the population and its characteristics

The age structure of a population is determined by the number of organisms of a particular age in the population.
The ratio of the number of different age groups is the result of the action of two opposite processes: reproduction and mortality. The age composition of the population depends on the size of the birth rate and the intensity of the death rate of organisms.

The age structure of the population is expressed using age pyramids, in which the length of the stripes indicates the percentage of individuals of each age rank in the total number.

Example: The figure shows the age pyramids of a person in two countries (Afghanistan and Belgium).

In growing populations (age pyramid in Afghanistan):

• fertility exceeds mortality,
• the number is increasing.

In a stable population (age pyramid in Belgium):

• fertility is equal to mortality,
• the population size remains almost unchanged,
• groups of different ages are approximately equal.

The study of the ratio of age groups makes it possible to assess the change in the number of individuals in the populations in the near future. This is important, for example, for hunting. You can determine which group of individuals needs protection, and which one can be allowed to hunt.