Class 10 Environment and Population and Health Note


Unit 1


Demography is the measurement of the population of a specific place in a particular time and their scientific study. Demography means the statistical and mathematical study of population size, regional distribution, composition and population change. Demography can also be stated as the scientific study of human population.


Major sources of population statistics:

Statistics is the study of the collection, analysis, interpretation, presentation, and organization of data. In applying statistics to, e.g., a scientific, industrial, or societal problem, it is conventional to begin with statistical population or a statistical model process to be studied. The major sources of population statistics are as follows:

1. Primary Sources

2. Census

3. Vital registration

4. Sample survey

5. Administrative records

6. Secondary sources

7. Organizations and institutions

8. Books

9. Journals

10. Newspaper



A population is a summation of all the organisms of the same group or species, which live in a particular geographical area, and have the capability of interbreeding. In human population, Population is the number of people living in specific area.


World population:

For humans, population density is the number of people per unit of area, usually quoted per square kilometer or square mile which include or exclude, for example, areas of water or glaciers. Commonly this may be calculated for a county, city, country, another territory, or the entire world.

The world's population is around 7 billion, and Earth's total area (including land and water) is 510 million square kilometers (197 million square miles). Therefore the worldwide human population density is around 7 billion ÷ 510 million = 13.7 per km2 (35 per sq. mile).


Density of population of Nepal:

Population density in Nepal is also increasing along with the rapid growth of population. Due to limited land areas of the country, it is natural that population density increases simultaneously with the growth in the population. Looking at the condition of population density in different censuses from 1981 to 2001 AD, it is found that population density has increased in all development regions. However, it has increased drastically in the Terai region in comparison to the hills and the mountains regions. Population density has also increased rapidly in the country as a whole. The density of population was 102 persons in 1981, 126 persons in 1991 and it reached 157 persons in 2001 AD. From this fact, we can clearly consider Nepal as one of the density populated countries in the world. Our country is also full of inequality in terms of population density by geographical and development regions. The population growth rate in the central development region is the highest of all development regions. The main reason behind this is the migration of people to this development region due to the availability of fertile soil and various other facilities and services.


The major factors responsible for the increasing population in Nepal are;

1. Early marriage and child marriage.

2. Polygamy

3.  Ignorance and illiteracy of the people

4. Poverty

5. Importance of son in the family

6. Role of children in economic status

7. Low status of women in the society

8. Lack of population education

9. Concept of more children means more income

10. Lack of women employment

11. Higher rate of infant mortality

12. Social superstation etc is the main factor in the contest of Nepal.


Composition of population:

Population composition is the description of a population according to characteristics such as age and sex. These data are often compared over time using population pyramids. The composition of the population is part of the social environment. It provides a framework against which to interpret the health status and behaviors of the population.

Composition of population can be classified and studied by the following ways;

1. Population composition by sex

2. Population composition by age

3. Population composition by occupation

4. Population composition by religion

5. Population composition by caste

6. Population composition by language

 From such study of population composition, can get the idea of the population structure of a place, area or country. The number of males, females, children, adults and elderly are taken in to account. The total population can be divided in many ways for the systematic and scientific study of population composition. The different societies are formed on the basis of sex, age, caste, language, religions and occupation. The scientific study, research and analysis of every aspect of population of any country or region have direct relation with the composition of population. The structure and situation of a particular community or society of the country can be depicted by the composition of population.

Hence the real picture of a certain community or society is presented by population composition.


Population data:

Population data can be obtained from different sources. Two major sources are:

1. Primary sources

2. Secondary sources

There are four types of sources of primary data namely Census, Vital registration system, Sample Surveys, Administrative Records. Secondary sources refer to those data that are already collected and compiled by other national and international organizations.

Data are needed for explaining the distribution of population because:

1. From the data we are clear cut idea about the population situation can be visualized and the plans and policies can be made for the existing population for their progress and development. Therefore data are needed for explaining the distribution of population.

2. Data are used to find out the number of present and future voters.

3. They are also useful for international compression.

4. Data report is also used by individual scholars and researchers.

5. Demographer needs census data to make precise projection of future population.

6. It is useful to prepare life table.

7. It is also useful for policy maker, researcher, economics, politicians, statisticians and other to perform social activities.

8. It is useful to formulate future plans.

9. Data records also help on many others needs.


Demographic measures:

The measurement of the three components of fertility, mortality and migration are necessary for the proper analysis of population. The rates of fertility, mortality and migration are used for measuring population changes using different formula. Necessary figures are calculated from these measures. We can analyze the changes in size, composition and distribution of population. Moreover, the trend of the changes of population in the future can also be analyzed.

The fertility rate can be obtained in the following ways:

1. Crude Birth Rate,

2. General Fertility Rate

3. Age Specific Fertility Rate

4. Total Fertility Rate

The mortality rate can be obtained in the following ways:

1. Crude Death Rate

2. Age Specific Death Rate

3. Infant Mortality Rate

The migration rate can be obtained in the following ways:

1. In Migration Rate

2. Out Migration Rate

3. Net Migration Rate

4. Gross Migration Rate



Migration is the process of transferring of people from one place to another place for permanent settlement. Migration affects the distribution of population of the place. The distribution of the population of the particular place will be affected because due to urbanization the people will migrate to urban areas which will definitely increase the population of that place. Similarly the population of the urban areas will decrease accordingly. In this way migration creates uneven distribution of population. So migration is not a good factor in population because people do not migrate to rural areas where there are ample natural resources. The proper exploitation of natural resources is decreasing due to migration.

The factors affecting migration are age, sex, family status and occupation. They are described as follows:

1. Age:

In both of the internal and international migration, young age people migrate more than the people of other age groups. One of the reasons behind this is that young people can easily adapt in a new place, society or climate. The number of migrants from children, old age groups is very low in comparison to the young and economically active population.

2. Sex:

Internally, female migrate more than males because they have to leave their parents home and go to their husband's home after they get married. Males migrate in search of work.

3. Family status:

The status of a person also affects migration. Young and unmarried people migrate more than the married and people of other age group.

4. Occupation:

People have to migrate from their birth place to new place for occupation. By the nature of work people do migrate from one place to another place.


Measures of Migration:

1. In-Migration Rate:

The rate of number of people migrating to certain place is called the in-migration rate of that place.

Mathematically it can be calculated by;

                                                  ${\rm{IMR}} = \frac{{\rm{I}}}{{\rm{P}}}{\rm{*}}1000$


2. Out-Migration Rate:

The rate of number of people migrating from certain place is called the out-migration rate of that place.

Mathematically it can be calculated by;

                                                ${\rm{OMR}} = \frac{{\rm{O}}}{{\rm{P}}}{\rm{*}}1000$


3. Net Migration Rate:

The difference between the number of people in migrants and the number of out migrants is called net migration rate.

Mathematically it can be calculated by;

                                     ${\rm{NMR}} = \frac{{{\rm{I}} - {\rm{O}}}}{{\rm{p}}}{\rm{*}}1000$


4. Gross Migration Rate:

Gross Migration Rate refers to the total number of immigrants and emigrants and divided by mid-year population of that year multiplying by 1000.

Mathematically it can be calculated by;

                                     ${\rm{GMR}} = \frac{{{\rm{I}} + {\rm{O}}}}{{\rm{P}}}{\rm{*}}1000$



The sex ratio is the ratio of males to females in a population. It is generally denotes the number of males per 100 females this can be derived from following formula:

Sex-ratio = $\frac{{\rm{m}}}{{\rm{n}}}{\rm{*}}100$


M = total male population in particular year

F = total female population in particular year



Factors that affect birth:        

There are various biological factors affecting birth. The biological factors affecting birth are heredity, age, ovulation, lactation, miscarriage and health. Any three of them are described below:


Heredity affects birth because the problems related to reproductive organs; reproductive process and infection of sexually transmitted diseases have negative effects on fertility.


People become fecund after they reach certain age of maturity. Girls become fecund after they reach the age of 14-15 and they can conceive upto the age of 49. Therefore age is the biological factor affecting birth.


Healthy man has healthy life and their child bearing capacity is affected by their health also. Therefore health is the biological factor affecting birth.


Factors that affecting death:

The factors affecting death rate are heredity, sex, senescence, diseases, level of nutrition, health services and facilities and health education. Any four of them are described below:


Longevity of life is characteristics of heredity. Long life is attributed to heredity. Some people whose forefather lived for a long period of time are also living longer. Longevity of human life depends on the environment where they are born and brought up.


It has been found that female live longer than males. This trend has not only been seen in a certain countries but everywhere in the world. It has also been found that infant mortality rate for boys are higher than for girls.


This is the age of science and technology. In spite of great development of science and technology, scientists have not been able to prevent death. People have to lose their life being the victim of infectious, fatal and hereditary diseases.

Level of nutrition:

Food is one of the bases of life. Continuous intake of nutritious food is as important as air and water for the survival of life. Lack of nutritious food makes people fight against diseases which ultimately take the life towards death.


Short-cut formula of Demographic Measures:


1. In-Migration Rate:

                                                  ${\rm{IMR}} = \frac{{\rm{I}}}{{\rm{P}}}{\rm{*}}1000$


2. Out-Migration Rate:

                                                ${\rm{OMR}} = \frac{{\rm{O}}}{{\rm{P}}}{\rm{*}}1000$


3. Net Migration Rate:

                                     ${\rm{NMR}} = \frac{{{\rm{I}} - {\rm{O}}}}{{\rm{p}}}{\rm{*}}1000$


4. Gross Migration Rate:

                                     ${\rm{GMR}} = \frac{{{\rm{I}} + {\rm{O}}}}{{\rm{P}}}{\rm{*}}1000$


5. Sex-ratio:

Sex-ratio = $\frac{{\rm{m}}}{{\rm{n}}}{\rm{*}}100$


6. Total dependency ratio:

Total dependency ratio = $\frac{{{\rm{no}}.{\rm{of\: people\: aged\: }}0 - 14{\rm{\: and\: }}60{\rm{\: and\: above}}}}{{{\rm{no\: of\: people\: }}15 - 59}}{\rm{*}}100$


7. Crude Birth Rate:

CBR = $\frac{{\rm{B}}}{{\rm{P}}}{\rm{*}}1000{\rm{\: }}$


8. Crude Death Rate CDR:

CDR = $\frac{{\rm{D}}}{{\rm{P}}}{\rm{*}}1000{\rm{\: }}$


8. Population doubling Time:

${\rm{Population\: doubling\: Time}} = \frac{{70}}{{{\rm{PGR}}}}$          


9. Population Growth Rate:

                     ${\rm{PGR}} = \frac{{{\rm{CBR}} - {\rm{CDR}} + {\rm{NMR}}}}{{1000}}{\rm{*}}100$


10. Rate of Natural Increase:

${\rm{Rate\: of\: Natural\: Increase}} = \frac{{{\rm{CBR}} - {\rm{\: CDR}}}}{{1000}}{\rm{*}}100$


11. Infant Mortality Rate:

                       ${\rm{Infant\: Mortality\: Rate}} = \frac{{{{\rm{D}}_0}}}{{\rm{B}}}{\rm{*}}1000$


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