NCERT Class 9 Solutions: Population (Contemporary India-I) Chapter 6– Part 4
Q-2. Answer the following questions briefly.
(iii) Define age structure, death rate and birth rate.
Age Structure describes distribution of people among various ages. We can then divide the population among the various age groups for further analysis and planning. For example, the number of schools in an area will be decided (planned) using the population data between the age group of 0-15 years (Children). For example, we can divide the population into following coarse age groups:
Children (up to 14 years)
Working age (15 – 59 years)
Aged (60 years and above)
Below chart divides the population into more fine grained age groups:
When we divide the population as above, the resulting curve is known as a population pyramid. It tells us for each population group how many young people are there to support them. For example, in the above graph there are many young adults to support the old (and likely) dependent population.
Following are other possible shapes of population pyramids. From rapidly expanding population to contracting population. Note that in 4 there is a problem because in a few years very few adults would have to support a larger ageing population.
The number of deaths per 1000 persons is known as death rate according to latest census, for India it is around 7.4 deaths per 1000.
The number of live births per 1000 persons is known as birth rate according to latest census, for India it is around 20 births per 1000.
(iv) How is migration a determinant factor of population change?
Migration within the country is called internal migration and between two countries is called international migration.
Internal migration does not affect population size but it affects the population composition of regions within a country.
When a person leaves an area or country it is known as emigration and when they enter another area or country it is known as immigration.
International migration can either increase or decrease population growth depending on the degree of immigration and emigration.