1. Lesson 10:
Population Changes
P.B. Dharmasena
0777 - 613234, 0717 - 613234
dharmasenapb@ymail.com , dharmasenapb@gmail.com
https://independent.academia.edu/PunchiBandageDharmasena
https://www.researchgate.net/profile/Punchi_Bandage_Dharmasena/contr
ibutions http://www.slideshare.net/DharmasenaPb
Poverty and Environment
Course code: ECON/EMGT 4214
Friday from 8.30-11.30 a.m

2. Population Changes - Content of the Lesson
• Nature controls population
• Factors affecting population
• Demographic transition
• Control of population
• Social policy of US on
immigration

3. Population Change
Higher Human Biology

4. Population
A population is a group of individuals of the same
species which makes up part of the community in
an ecosystem.
When a population colonises a new environment
the population increases rapidly until it reaches
the carrying capacity - the maximum population
size that can be maintained by the environmental
conditions.
Time
Population
size

6. Populations terminology
Population density – the number of individuals of
the same type present per unit area (or volume)
of a habitat.
Birth rate – the number of new
individuals produced by a
population during a certain time
interval.
Death rate – the number of
individuals within a population that
have died during the same time
interval.

8. Population Growth Curve
Time
Number of
Individuals
Carrying
capacity
Exponential growth
Rapid increase in
population size
Birth = Death
rate rate
Population
colonising
a new
environment

9. Population Stability
When the population reaches the level that the
available environmental recourses can just maintain
the population becomes stable.
At this stage it is in a state of dynamic equilibrium
(there are very slight changes but overall it is
relatively balanced) and the population has reached
its carrying capacity and birth rate equals death
rate.
Human interference has caused many populations to
become unstable or threatened.

10. The carrying capacity is determined by:
Population Regulation
• Food
• Oxygen
• Water
• Space
If one is
limited it
prevents the
population
increasing
Regulatory
Effect
• Predation
• Disease
• Pollution by organism’s waste
Population
decrease
Death by….

11. Regulation of population size
Population at
Carrying capacity
(maximum supported by
the environment)
factor limited
e.g. food, water
Population
decrease
Population
increase
Population
decrease
Death rate increases
Factor plentiful
e.g. food, water
Population
increase
Birth rate increases

12. Agricultural
Humans have overcome causes of mortality (e.g.
predation) so have increased our carrying
capacity & have increased exponential growth.
Human Population Explosion
Revolutionary changes
Rapid population
increase
Industrial

13. • Totally dependent
on immediate
environment for
food, water, shelter.
• Hunter- gatherer
societies or pre
agriculture societies
•Live ‘hand to
mouth’
• No agriculture
• No modern
technology
Undeveloped Societies
Limitation to population increase:
Wild animals
Violence
Diseases
Climate (temperature, water shortage etc.)

14. Aborigines
(Australia)
e.g. Hunter-gatherers
• remote locations
• low carrying capacity
• low population density
• shared society
Arctic Inuit (Eskimos) Population limited
by water
availability
Population limited by
low temperature

15. Influence of modern society on
undeveloped societies
Modern societies have introduced:
• tools
• technology
• disease – led to a population decline
Caused problems:
• Less land to live off
• Traditional cultures are disappearing
• Economic & social problems

16. • Grow crops on own land to meet the families own needs.
• Store excess crop for use during times of shortage
• Rarely sell any crops or animals
• Use basic tools
• Use family labour
Subsistence farming
Common in
Latin
America,
Africa &
Asia

17. • Low standard of living
• Often no electricity or
sanitation
• Lifestyle similar to
10,000 years ago at
start of agricultural
revolution
• Population was in
increasing trend
Subsistence farming

18. Population Changes - Content of the Lesson
• Nature controls population
• Factors affecting population
• Demographic transition
• Control of population
• Social policy of US on
immigration

19. Factors affecting population change
• Density dependant factors
– Intra specific competition
– Predation
– Alle effect
• Density independent factors
– Natural disasters
– External invasions
– Limited resources in the ecosystem

24. Minimum viable population

28. Population change affects entire
ecosystem
• A change in one population of species can
affect the entire hierarchy of living things in
that ecosystem

29. Piped water
Immunisation
against diseases e.g.
smallpox & polio
Better
housing
Effect of Science on Human
Population Growth
Antibiotics
Modern
sanitation
Improvements
in child care
Efficient food
production

31. The World’s Population
• Population growth rate prior to 1650 was two-thousandths
of a percent per year
• In 1650 the world’s population was around 500 million
• By 1900 the growth rate was half of 1 percent with the
world’s population at around 1 billion
• By 1940 the growth rate rose to one percent
• Today the world’s population is about 6,602,000,000
• If the world’s population continues to grow at the present
rate, it will double in a mere 45 years, thus creating major
problems of migration, environmental pressure, and
resource management

32. Effect of Science on Human
Population Growth
1650 AD
Advances in
science
Scientific
discoveries
&
Inventions
Industrial
revolution
Advances
in
medicine
These advances have contributed to a human
population boom by removing limiting factors that
in the past regulated the population.

33. Exponential Growth of
Human Population
The human population is now growing exponentially
due to:
Overcoming
predation
(due to guns)
Less child
mortality
Increase in
life expectancy
Increased
female
fertility

34. Fertilisers
Exponential Growth
Also due to…
Increased food
availabilityMachinery
Pesticides

35. Change in Cultural Habits
Women tend to suckle their young for less time,
as ovulation is inhibited during breast-feeding,
women are more likely to conceive their next
child sooner.
Births no longer
spaced out
Birth rate
increases

36. Doubling time
… the length of time for the worlds population
to double.
In 1980s
doubling time
was decreasing
steadily thus
the world
population was
rapidly
increasing
Actually the population
growth rate is slowing
down due to…
• use of contraception
• social pressures (e.g. China)
• deaths from AIDS

37. World’s wealth is not
distributed evenly
The highest population
growth is in the poorest
nations so 50% of the world
population live in poverty!

38. Population Changes - Content of the Lesson
• Nature controls population
• Factors affecting population
• Demographic transition
• Control of population
• Social policy of US on
immigration

39. Measures of Population Growth
• One measure of population growth is the crude
birthrate - the number of births per 1,000
population
• The difference between the crude birthrate and the
death rate is referred to as the rate of population
growth (natural increase)
• As a whole, the world is not reproducing at a
higher rate, but people are living longer

40. Measures of Population Growth
• Most nations have a population growth rate of .1 percent to
3.0 percent
• Industrial nations are at the low end with developing
nations at the high end of the growth rate
» In the near future, the population of less
developed nations is likely to double
• Russia and many other European nations have been
experiencing extremely slow or even negative rates of
natural population increase

41. The Demographic Transition
• Demographic transition is the process by which
populations change through patterns of high-low
birth rates and high-low death rates
• The first stage of demographic transition is when
births and deaths cancel each other out and growth
is slow
»First stage is associated with poor
sanitation, disease, primitive farming,
and lack of medical knowledge

42. The Demographic Transition
• The second stage is associated with rising birth
rates and declining death rates
• Rapid growth
»Improvements in sanitation
»Nutrition
»Medicine
»Occurred first in Northwest Europe
»Second stage is found in most
developing nations today

43. The Demographic Transition
• The third stage is associated with low birth rates
and low death rates
• This third stage is found today in most developed
nations

44. Population Changes - Content of the Lesson
• Nature controls population
• Factors affecting population
• Demographic transition
• Control of population
• Social policy of US on
immigration

45. Rising Expectations
• Rising expectations is the belief that one’s
immediate environment is capable of providing
benefits – that conditions are improving
• Improvements in living conditions in developing
countries has led to rising expectations
• Rising expectations is related in part to the
relationship between the standard of living in a
country – what people want or expect in the way
of material well being and the level of living – and
what one actually obtains

46. Rising Expectations
• In part, rising expectations have been a function of
the growth of literacy in developing nations
• The gap in living standards between the haves and
have not is a social problem:
»Political instability
»Backwardness
»Neocolonialism
»Terrorism
»Population migration of the poor
Neocolonialism - the control of less-developed countries by developed
countries through indirect means

47. Food and Hunger
• Three-quarters of a billion people are hungry in a world
where there is plenty to eat
• Children account for 75 percent of hunger-related deaths
• Hunger is a paradox in that there is an abundance of low
cost food, but the poor lack the income to purchase food
and to have access to food
• Poverty and politics are, by far, the primary causes of
hunger in the world
• One of the paradoxes of world hunger is that food supplies
have been increasing over the past twenty years while the
cost of food has been decreasing

48. Population Control
• Population control usually takes three approaches
• 1. Reduce the birthrate of a population
• 2. Control fertility to achieve zero rate of
population growth
• 3. Achieve a negative rate of growth reducing the
size of the population

49. Family Planning
• Family planning involves the
voluntary control of the
number of children born
• Education
• Contraceptive use to control
family size

50. Zero Population Growth (ZPG)
• Zero Population Growth is an organization that
advocates no population growth as soon as
possible, through measures like:
»Birth control
»Legalized abortion
»Education and changing attitudes on
family

51. Population Control in LDCs
• Sterilization – encouraged volunteers through
financial incentives
• China and one child per family policy
• Family planning and birth control, along with
educational programs

52. Population Changes - Content of the Lesson
• Nature controls population
• Factors affecting population
• Demographic transition
• Control of population
• Social policy of US on
immigration

53. The U.S. Population
• The United States’ population is growing at a rate
of about 1 percent a year
• Sixty percent is due to natural growth - births over
deaths
• Forty percent is due to net migration
• Age and income disparity of old and new
immigrants

54. Immigration and Its Consequences
• Many immigrants came to the United States for a
better way of life
• Freedom
• Jobs and economic opportunities
• The diversity has been an important source of the
culture

55. Immigration and Its Consequences
Immigration has also led to problems
• Ethnic and racial conflict
• Competition among nationalities for a
share of American economy
• Debates over immigration policy
• Illegal immigrants
• Costs of immigration

56. Immigration to the United States:
A Brief History
The Early Colonial Period (to 1790)
• Immigrants from Great Britain accounted for 77
percent of the population
• African and native-born slaves accounted for 19
percent
• German 4 percent
• Irish 3 percent
• Dutch 2 percent

57. Immigration to the United States:
A Brief History
Old Northwest European Migration, 1820-1885
• Majority of immigrants from this period were
from:
• Germany
• Ireland
• England
• China from 1840s to 1880s

58. Immigration to the United States:
A Brief History
• The Intermediate Migration from Southern
and Eastern Europe (1885-1940)
• Major immigrant groups during this period were
• Italians
• Poles
• Hungarians
• Serbians
• Croatians – A Slavic group with the origin from
Iran/ Afganishthan

59. Immigration to the United States:
A Brief History
The Post-World War II Refugee Period (to 1968)
• Political and religious refugees from post-World War II
countries
The New Immigration (1968-Present)
• Immigration was geared to
• Family reunification
• Needs of U.S. economy

60. Immigration to the United States:
A Brief History
Major immigrant groups during this period were
• Greeks
• Jews
• Russians
• Anti-immigrant movement and restrictionist
policies
»Immigration act of 1921

61. Immigration to the United States:
Presence
• Once Again a Nation of Immigrants
- In the past few years the United States has been turning
once again into a nation of immigrants.
– Most immigration, both documented and
undocumented, is from:
– Mexico and Central and South America
– Asian continent

62. Urban Concentration of Immigrants
• Majority of new immigrants have largely settled in
a few regions and cities
• New York
• Los Angeles
• Miami
• Chicago
• Mexicans in the Southwest
• Chain migration - referring to the tendency of
immigrants to settle in ethnic communities

63. Undocumented Immigrants
• Primary concentration of undocumented workers are in
Western and Southwestern states
• Smuggling and exploitation
• There are economic benefits and costs associated with
undocumented immigrants
• Modes of Entry to the United States
• Nearly half of all undocumented immigrants arrive
legally as visitors to the U.S., but as much as 45 percent of
these people become overstayers
• It is not clear exactly what effect illegal residents have
on the U.S. economy

64. Social Policy
• Terrorism and war have fueled a new anti-
immigrant movement in the United States
• Policies will focus on the debate between the
benefits and costs that immigrants will bring to
American Society
• Immigration Reform and Control Act of 1986 -
making employers liable for hiring undocumented
immigrants

65. Social Policy
• Welfare reform initiates related to legal
immigrants and undocumented immigrants will
continue
• International population control initiates in
developing countries will take on renewed
significance
• Social-scientific evidence plays an important part
in the debates about immigration policies
• The policy of family reconciliation is highly
popular among immigrants and strongly opposed
by conservatives