3.human population and environment

Unit - 3
Human population and environment

Human population :-
                                    The anastors of modern man came Into existent on earth some 1,00,000 to 2,00,000 years ago. The   modern man came into existence 50,000 years ago. In the beginning the population was low . In 1850 it rose to 1 billion in 1930 it  become 2 billion by 2000 it rose to  6.1 billion. In  2008 in the world population was 6.7 billion this number could rise to more than 9 billion in the next 50 years . So population has increased six fold in the last 150 years.

Population:-
Population  is the number of individual organism of this sum spices in given area.
Demography :- the study of human population is called demography.
 population density:- population density is the measurement of the number of people in area. population density is an average number. It  is calculated by dividing the number of people by area.

                                       Number of people /area (per sq.km)

 Structure:-  population growth or decrease(change) result from the interaction of 3-4 variables:
1) birth 2) death 3) migration 4) age  and sex structure. In Every population there are three age groups.1) pre reproductive 2) reproductive and 3) post reproductive. Natural increase accounts for the greatest amount of growth in population specially within short period of time when the numbers of births  is greater than the number of deaths ,the population grows.
            The measurement of human population growth is done through average annual growth rate.
average annual growth rate in percentage= (P1-P2)/(P1×N)*100
P2 = population size as per present census
P1= population size as per last census                                          
N= the period of time between two sensors( in years)

Birthrate :- birth rate is the number of new birth for every 1000 persons. birth rate can be controlled through family planning.
Death rate:- death rate  is the number of deaths per 1000 persons.a decreasing rate of death results into an increase in population growth rate.
Migration :- the exit or entry of new individuals from an area or into the area is called migration.
The population size decreases or increases on basis of the difference between individuals exiting and arriving.

💝  Reason for population growth
Human population grew rapidly  during the industrial revolution because of the fall in death rate this mortality revolution began in the 1700s in Europe and spread to north america by the 1800. Death rate fall as  new farming and transpotation Technology expandod the foo supply and lessened the danger of Farmine.
Industrialization improved public health and living standards.in the past and Fact and childhood deaths  and short life spans used to Limit population growth. in today's world due to improved nutrition, sanitation and medical care.more  baby survive their first few years of life the combination of continuing high birth rate and a low death rate is creating a rapid population increase  in many countries and people live longer.


● over population and population explosion
   Over population is defined as a condition of having more people than  can live on Earth in comfort , happiness and health and still leave the world a fit place for future generations.
The current population growth and demands in increasing needs for food, water, space, Healthcare, technology and education Asian holds the majority of the world's people. so massive efforts are needed to keep social and economic condition from deteriorating further.
Population explosion
The steep population increase over a short period of time is called population explosion.
There is the 3.3 Births for each death in less developed countries. the combination of the High birth rate and death rates has led to the population explosion in many countries through out  the world. After millions of yours of extremely slow growth,the human population indeed grow explosively doubling again and again a billion people were added between 1960 and 1975. Throughout the 20th century each additional billion has been added in a short period of time. Human population entered the 20th century with 1.6 billion people and left the country with 6.1 billion.in 2008 population was 6.7  billion. This number could rice to more than 9 billion in the next 50 years.
              At the present, the natural growth rate of world human population is 18 % the growth curve is J shaped. the population growth is not uniform over the entire world more developed countries like Europe, North America,Russia and Japan collective show on natural growth rate of 0.6 % less .developed country of Africa, Asia, Latin America possess a natural growth rate of 1.8 % higher.
● Effects of population growth /problems related with over population


It can lead to poverty and hunger.
It can cause  habitat destruction and loss of biodiversity.
It will affect on Children's growth and health.
It will lead to unemployment slum development squatler self comments lack of across to education, health care, drinking water sanition and family planning services.
There will be economic inequality between the developed and developing world.
It will cause a decline  in the nature resources.
It can cause pollution through human activities and industries by human.

Environment and human health