While studying exponential growth we need to know more than just the birth and death rates because these rates vary with age and sex. Age structure in a population is important because individuals vary in their age and many functional aspects are linked with age.
For example, women can bear children i only between ages of 15-44 years, also infants (children under 1 year of age) and older people have higher rates of mortality as compared to individuals of intermediate ages. Accordingly a population can be subdivided into three sub groups.
For a more detailed understanding of the age-structure individuals of a population are divided into age groups with 5 or 10 year interval. Further, males and females can be shown separately in a diagram. Alternately age-sex distributions are also drawn by plotting the percentage of the population of each sex in each group.