NCERT / CBSE NOTES | Class 8th (VIII) : Chapter Summary
Population change refers to the change in the number of people due to birth, death and migration during a specific time.
Birth rate is the number of live babies born in a year for every 1000 people in the total population. Death rate is the number of people dying per 1000 people. The difference in the birth rate and the death rate of a country is called the natural growth rate.
A rapid growth in population is referred to as population explosion. If the birth rate is more than the death rate, then there is an increase in population. If the death rate is more than the birth rate, then there is a decrease in the population. A decrease in population is known as depopulation.
If birth rate and death rate are at the same level, there will be no natural growth. Migration is another cause of change in the size of a population which is the movement of people into and out of an area.
People who leave a country are called emigrants, while those who arrive in a country are called immigrants. A search for better employment opportunities is the main reason behind international migrations.
The pattern of population growth varies from country to country.
Population Density and Distribution
Humans are the ultimate resource of nature, and are referred to as human resources. In India, a Ministry of Human Resource Development was created in 1985 with the primary purpose of ensuring that the people of India are healthy, educated and motivated.
The pattern in which people are spread across the earth is known as population distribution. The number of people living in a unit area of the earth’s surface gives the density of population. Population density is calculated by dividing the number of people by area and is usually expressed as the number of people per square kilometre.
The average density of population in the whole world is 45 persons per square kilometre. The population density of a place depends on a range of geographical and socio-economical factors. The topography of a place, its climate and availability of resources like water, soil, minerals, social, cultural and economic factors are some geographical factors that affect the population of a place.
The development of a country depends on the quality of the people that comprise the population. The quality of the people can be determined by studying their age, gender, literacy level and health condition.
The population structure of a country helps us determine the number of males and females, and their age groups. The most common method of showing the population structure is through a population pyramid, also called an age-sex pyramid.
It shows the distribution of males and females in a country by their age groups. The total population is divided into various age groups, and the percentage of the total population is subdivided into males and females.
A broad population pyramid at the base indicates the percentage of young people is high while a tapered pyramid becoming narrow at the top indicates a very small percentage of the population is elderly.
The width of the base of the pyramid indicates the birth rate of a country. Its slope can indicate the death rate and its height indicates the life expectancy.