Tính động ở quần thể người - Lê Hoàng Ninh

TÍNH ĐỘNG Ở QUÂN THỂ NGUOI 
 HUMAN POPULATION DYNAMICS 
GS LÊ HOÀNG NINH 
Các vấn đề cần được lưu ý 
Lịch sử phát triển dân số / quần thể người và 
liêu sẽ có bao nhiêu người vào năm 2050? 
Đô lớn của dân số bị ảnh hưởng bởi sinh, khả 
năng sinh sản, tử vong, di cư, nhập cư như 
thế nào? 
Dân số bị ảnh hưởng bởi tỷ lệ nam và nữ ở 
mỗi độ tuổi như thế nào? 
Chúng ta làm chậm sự phát triển dân số như 
thế nào? 
Nghiên cứu trường hợp : dân số thế 
giới quá đông ? 
The world’s population is projected to 
increase from 6.6 billion to 8.9 billion 
between 2006 and 2050. 
The debate over interactions among 
population growth, economic growth, 
politics, and moral beliefs is one of the 
most important and controversial issues 
in environmental science. 
Core Case Study: Is the World 
Overpopulated? 
Much of the 
world’s 
population 
growth occurs in 
developing 
countries like 
China and India. 
Figure 9-1 
Core Case Study: Is the World 
Overpopulated? 
Some argue that the planet has too 
many people. 
Some feel that the world can support 
billions of more people due to 
technological advances. 
There is a constant debate over the 
need to reduce population growth. 
Must consider moral, religious, and 
personal freedom. 
HUMAN POPULATION GROWTH: 
A BRIEF HISTORY 
The human population has grown 
rapidly because of the expansion of 
agriculture and industrial production 
and lower death rates from 
improvements in hygiene and medicine. 
In 2006, the population of developed 
countries grew exponentially at 0.1% per 
year. 
Developing countries grew (15 times faster 
at 1.5% per year. 
Where Are We Headed? 
We do not know how long we can continue 
increasing the earth’s carrying capacity for 
humans. 
There are likely to be between 7.2-10.6 billion 
people on earth by 2050. 
97% of growth in developing countries living in 
acute poverty. 
What is the optimum sustainable population of 
the earth based on the cultural carrying capacity? 
Where Are We Headed? 
U.N. world 
population projection 
based on women 
having an average of 
2.5 (high), 2.0 
(medium), or 1.5 
(low) children. 
Figure 9-2 
Fig. 9-2, p. 173 
High 
10.6 
High 
Medium 
Low 
Low 
7.2 
Medium 
8.9 
Year 
Những yếu tố ảnh hưởng đến kích cỡ 
dân số 
Population increases because of births 
and immigration and decreases through 
deaths and emigration. 
Instead of using raw numbers, crude 
birth rates and crude death rates are 
used (based on total number of births 
or deaths per 1,000 people in a 
population). 
 Age Structure: Young Populations 
Can Grow Fast 
How fast a population grows or declines 
depends on its age structure. 
Prereproductive age: not mature 
enough to reproduce. 
Reproductive age: those capable of 
reproduction. 
Postreproductive age: those too old to 
reproduce. 
Limits on Population Growth: 
Biotic Potential vs. Environmental 
Resistance 
 No population can increase its size 
indefinitely. 
The intrinsic rate of increase (r) is the rate 
at which a population would grow if it had 
unlimited resources. 
Carrying capacity (K): the maximum 
population of a given species that a 
particular habitat can sustain indefinitely 
without degrading the habitat. 
Exceeding Carrying Capacity: Move, 
Switch Habits, or Decline in Size 
Over time species may increase their carrying 
capacity by developing adaptations. 
Some species maintain their carrying capacity 
by migrating to other areas. 
So far, technological, social, and other 
cultural changes have extended the earth’s 
carrying capacity for humans. 
Population Density and Population 
Change: Effects of Crowding 
Population density: the number of individuals 
in a population found in a particular area or 
volume. 
A population’s density can affect how rapidly it 
can grow or decline. 
• e.g. biotic factors like disease 
Some population control factors are not affected 
by population density. 
• e.g. abiotic factors like weather 
Survivorship Curves: 
Short to Long Lives 
The populations 
of different 
species vary in 
how long 
individual 
members typically 
live. 
Figure 8-11 
Fig. 8-11, p. 169 
Age 
Early loss 
Late loss 
FACTORS AFFECTING HUMAN 
POPULATION SIZE 
Average crude 
and birth rates 
for various 
groupings of 
countries in 
2006. 
Figure 9-3 
Fig. 9-3, p. 174 
Average crude 
death rate 
Average crude 
birth rate 
World 
21 
9 
All developed 
countries 
11 
10 
All developing 
countries 
27 
8 
9 
23 
Developing 
countries 
(w/o China) 
Fig. 9-3, p. 174 
14 
Europe 
North 
America 
United 
States 
Oceania 
Asia 
Africa 
Latin and 
Central America 
38 
15 
21 
6 
20 
7 
17 
7 
14 
8 
8 
11 
10 
FACTORS AFFECTING HUMAN 
POPULATION SIZE 
The world’s 10 
most populous 
countries in 2006 
with projections 
in 2025. 
Figure 9-4 
Fig. 9-4, p. 174 
2025 
1.5 billion 
China 1.3 billion 
India 1.1 billion 
1.4 billion 
USA 300 million 
349 million 
Indonesia 225 million 
264 million 
Brazil 187 million 
229 million 
Pakistan 166 million 
229 million 
Bangladesh 147 million 
190 million 
Russia 142 million 
130 million 
135 million Nigeria 
199 million 
Japan 
121 million 
128 million 
2006 
Declining Fertility Rates: 
Fewer Babies per Women 
The average number of children that a 
woman bears has dropped sharply. 
This decline is not low enough to stabilize the 
world’s population in the near future. 
Replacement-level fertility: the number of 
children a couple must bear to replace 
themselves. 
Total fertility rate (TFR): the average number 
of children a woman has during her reproductive 
years. 
Case Study: Fertility and Birth Rates 
in the United States 
Nearly 2.9 million people were added to 
the U.S. in 2006: 
59% occurred because of births 
outnumbering deaths. 
41% came from illegal and legal 
immigration. 
Case Study: Fertility and Birth Rates 
in the United States 
In 2006, the total fertility rate in the United 
States was slightly > 2.0 
Figure 9-5 
Fig. 9-5, p. 175 
Replacement 
Level 
Year 
B
ir
th
s
 p
e
r 
w
o
m
a
n
Baby boom 
(1946–64) 
Case Study: Fertility and Birth Rates 
in the United States 
The baby bust that followed the baby 
boom was largely due to delayed marriage, 
contraception, and abortion. 
Figure 9-6 
Fig. 9-6, p. 175 
Demographic 
transition Depression 
End of World War II 
Baby boom Baby bust Echo baby boom 
B
ir
th
s
 p
e
r 
th
o
u
s
a
n
d
 p
o
p
u
la
ti
o
n
Year 
Fig. 9-7, p. 176 
 47 years 
Homicides per 
100,000 people 
Hourly manufacturing 
job wage (adjusted for 
inflation) 
Living in 
suburbs 
Homes with 
electricity 
Homes with 
flush toilets 
High school 
graduates 
Married women working 
outside the home 
Life expectancy 
1.2 
5.8 
$15 
$3 
52% 
10% 
99% 
2% 
98% 
10% 
83% 
15% 
81% 
2000 
1900 
8% 
77 years 
Factors Affecting Birth Rates and 
Fertility Rates 
The number of children women have is 
affected by: 
The cost of raising and educating them. 
Availability of pensions. 
Urbanization. 
Education and employment opportunities. 
Infant deaths. 
Marriage age. 
Availability of contraception and abortion. 
Factors Affecting Death Rates 
Death rates have declined because of: 
Increased food supplies, better nutrition. 
Advances in medicine. 
Improved sanitation and personal hygiene. 
Safer water supplies. 
U.S. infant mortality is higher than it could be 
(ranked 46th world-wide) due to: 
Inadequate pre- and post-natal care for poor. 
Drug addiction. 
High teenage birth rate. 
Case Study: U.S. Immigration 
Since 1820, the 
U.S. has 
admitted 
almost twice as 
many 
immigrants and 
refugees as all 
other countries 
combined. 
Figure 9-8 
POPULATION AGE STRUCTURE 
The number of people in young, middle, 
and older age groups determines how 
fast populations grow or decline. 
The number of people younger than 
age 15 is the major factor determining 
a country’s population growth. 
Changes in the distribution of a 
country’s age groups have long-lasting 
economic and social impacts. 
HISTOGRAMS (MILLER PG 179) 
POPULATION AGE STRUCTURE 
Populations with a large proportion of 
its people in the preproductive ages 1-
14 have a large potential for rapid 
population growth. Figure 9-9 
Fig. 9-9, p. 179 
Expanding Rapidly 
Guatemala 
Nigeria 
Saudi Arabia 
Expanding Slowly 
United States 
Australia 
Canada 
Stable 
Spain 
Portugal 
Greece 
Declining 
Germany 
Bulgaria 
Italy 
Prereproductive ages 0–14 Reproductive ages 15–
44 
Postreproductive ages 45–85+ 
Female Male Male Male Male Female Female Female 
POPULATION AGE STRUCTURE 
32% of the people in 
developing countries 
were under 15 years 
old in 2006 versus only 
17% in developed 
countries. 
Figure 9-10 
Fig. 9-10a, p. 179 
Female 
A
g
e
Population (millions) 
Developed Countries 
Male 
Fig. 9-10b, p. 179 
Female 
A
g
e
Population (millions) 
Developed Countries 
Male 
POPULATION AGE STRUCTURE 
Today, baby boomers make up nearly 
half of all adult Americans and 
dominate the populations demand for 
goods and services. Figure 9-11 
PARTS 
Broken down by age. You can see 
the birth rate, maturity rate and 
death rate of an entire population. 
Usually broken down by country. 
Expansive/rapid growth 
Birth rate exceeds the death rate. 
Population is getting larger. Pyramid 
shaped histogram. 
Ex’s. Kenya, Nigeria and Saudi 
Arabia. 
Stable/Slow Growth (Zero Growth) 
Birth rate almost equals death rate. The 
population is not getting any larger or is growing 
very slowly. Histogram shape is straighter and 
more box-like until about age 45-85. 
Ex. US, Australia & Canada has slow 
Denmark, Austria and Italy has stable 
Declining (negative growth) 
When the birth rate is smaller than 
the death rate. The pyramid bulges 
near the top or is inverted. 
Ex. Germany, Bulgaria & Hungary. 
Demography 
Definition: The study of human 
populations, their characteristics and 
changes. 
Population Explosion 
Anything that causes the population to grow 
uncontrollably. Ex. Baby boom. 78 Million 
person increase between 1946-1964. 
(Men came home from the war. These people all 
had children and so this increase will continue to 
move up through the country’s age structure as 
members of this group grow older) 
Exponential Growth- 
Growth of a population that 
increases by a fixed percentage of 
the whole in a give time. 
When plotted it looks like the 
letter J. 
Demographic Measures 
Statistics about people, such 
as births, deaths, and where 
they live as well as total 
population size. 
Density- number of people in a 
certain space. 
Birth rate(natality)- the number of 
births in a year per 1,000 people. 
Death Rate (mortality)- the number 
of deaths in a year per 1,000 people 
What factors affect death rates? 
1. Increased food supplies and distribution 
2. Better nutrition 
3. Improvements in medical & public health 
technology (ex. immunizations and 
antibiotics) 
4. Improvements in sanitation & personal 
hygiene 
5. Safer water supplies to stop spread of 
infectious disease 
Growth Rate- includes birth rate, death 
rate, immigration and emigration 
Doubling time- The time it takes for the 
population to double the number of 
people 
Gross National Product- The most 
commonly used measure of the 
economic growth of a country. 
Immigration- People coming into the 
population 
Emigration- The movement of people 
out of the population. 
Net Migration- Total number of 
people moving into or out of the 
population. 
Infant mortality rate- Number of 
child/infant deaths. 
If a mother lives in an area with 
a high infant mortality rate she 
will tend to have a lot of children 
to ensure some will make it to 
adulthood. 
Zero Population Growth- When the 
number of births, equals the number of 
deaths. No growth in the population. 
Total Fertility Rate- an estimate of the 
average number of children a women 
will have during her childbearing 
years. 
Replacement-level fertility- the number of 
children a couple must bear to replace 
themselves. It is slightly higher than two 
children per couple. (2.2 in developed 
countries and as high as 2.5 in some 
developing countries) 
It is greater in countries w/ high infant 
mortality rates than in countries w/ low 
infant mortality rates 
Age structure- Percentage of the 
population at each age level in a 
population 
Generation time- the time it takes 
for 1 generation to pass. 
Demographics of Countries 
Developing Countries- 
China is the largest but has taken drastic 
population control methods. 
By 2050, India is predicted to pass it. 
Pakistan is projected to become 3rd with 
Iran and Ethiopia following. 
However, Russia is losing 600,000 people 
a year, after being the 4th largest country 
in 1950. This is because of environmental 
pollution, hyperinflation, crime, corruption, 
disease and despair. 
SLOWING POPULATION GROWTH 
IN INDIA AND CHINA 
For more than five decades, India has 
tried to control its population growth 
with only modest success. 
Since 1970, China has used a 
government-enforced program to cut its 
birth rate in half and sharply reduce its 
fertility rate. 
Fig. 9-15, p. 186 
Total fertility rate 
Percentage 
of world 
population 
Population 
Population (2050) 
(estimated) 
Illiteracy (% of adults) 
Population under age 15 (%) 
Population growth rate (%) 
17% 
20% 
1.1 billion 
1.3 billion 
1.6 billion 
India 
China 
GDP PPP per capita 
Percentage living 
below $2 per day 
Life expectancy 
47% 
17% 
36% 
20% 
1.6% 
0.6% 
1.4 billion 
$5,890 
$3,120 
47 
80 
70 years 
62 years 
27 
58 
1.6 children per women (down from 5.7 in 1972) 
Infant mortality rate 
2.9 children per women (down from 5.3 in 1970) 
India’s Failed 
Family Planning Program 
Poor planning. 
Bureaucratic inefficiency. 
Low status of women. 
Extreme poverty. 
Lack of administrative financial 
support. 
Disagreement over the best ways to 
slow population growth. 
China’s Family Planning Program 
Currently, China’s TFR is 1.6 children 
per women. 
China has moved 300 million people 
out of poverty. 
Problems: 
Strong male preference leads to gender 
imbalance. 
Average population age is increasing. 
Not enough resource to support 
population. 
India’s Failed 
Family Planning Program 
Poor planning. 
Bureaucratic inefficiency. 
Low status of women. 
Extreme poverty. 
Lack of administrative financial 
support. 
Disagreement over the best ways to 
slow population growth. 
Developed countries 
Usually don’t have such 
population problems. It can 
be linked to poverty level 
even in developed countries. 
SOLUTIONS: INFLUENCING 
POPULATION SIZE 
Demographic Transition: As 
countries become economically 
developed, their birth and death rates 
tend to decline. 
Preindustrial stage: little population 
growth due to high infant mortality. 
Transitional stage: industrialization 
begins, death rates drops and birth rates 
remain high. 
Industrial stage: birth rate drops and 
approaches death rate. 
SOLUTIONS: INFLUENCING 
POPULATION SIZE 
Generalized model of demographic transition. 
Some developing countries may have difficulty 
making the demographic transition. 
Figure 9-14 
Fig. 9-14, p. 183 
Birth rate 
Death rate 
Total population 
Stage 1 
Preindustrial 
Stage 2 
Transitional 
Stage 3 
Industrial 
Stage 4 
Postindustrial 
Growth rate over time 
B
ir
th
 r
a
te
 a
n
d
 d
e
a
th
 r
a
te
(n
u
m
b
e
r 
p
e
r 
1
,0
0
 p
e
r 
y
e
a
r)
Low Low 
Low 
Increasing Very high Decreasing Zero Negative 
High 
Demographic stages in countries- 
 As countries becomes 
industrialized their birth rates 
decline. 
Pre-industrial 
Harsh living conditions lead to a 
high birth rate and high death 
rate. Thus, there is little 
population growth. 
Transitional 
As industrialization begins, food 
production rises and health care 
improves. 
Death rates drop and birth rates 
remain high 
The population grows rapidly 
Industrial 
Industrialization is wide spread 
The birth rate drops and eventually 
approaches the death rate. 
This is because of: 
 better access to birth control 
 decline in the infant mortality rate 
increased job opportunities for women 
the high cost of raising children who 
don’t enter the work force until after high 
school or college. 
Postindustrial 
The birth rate declines even further, 
equaling the death rate and thus 
reaching zero population growth. 
Then, the birth rate falls below the 
death rate and the total population 
size slowly decreases. 
(Cont.) 
37 countries have reached this 
stage. (mainly in W. Europe) 
To most population experts, the 
challenge is to help the remaining 
88% of the world to get to this 
stage. 
U.S. Statistics 
Because of the ‘Baby Boom’ the US 
has a bulge in the pyramid with 
people in their 50’s-60’s. 
There are also more women than 
men in the older age group because 
of differences in longevity between 
the sexes. 
(Cont) 
The US has a high % of retired 
people because of long life 
expectancy. This makes us realize 
the importance of social security, 
etc. 
The US is considered a slow 
growth population. 
Environmental Impact 
Developed Countries 
High rates of resource use 
 Result in high levels of pollution and 
environmental degradation per 
person 
 These are believed to be the key 
factors determining overall 
environmental impact. 
(Cont.) 
Urbanization 
What happens? Slums, fecal 
snow, disease 
This problem doesn’t exist too 
much in the US because of better 
working & housing conditions & 
air and water quality being 
improved. 
(Cont.) 
Urban areas must import most of 
its food, water, energy, minerals, & 
other resources. 
They produce enormous quantities 
of wastes that can pollute the air, 
water & land. 
44% of the world’s people live in 
urban areas that occupy only 5% of 
the world’s land & they consume 
75% of the world’s resources. 
Reasons for World Hunger Issues 
Unequal distribution of available food 
Loss of arable land 
Increasing population growth rate 
Increasing poverty in developing countries 
Reasons the human population has 
been so dramatic in the last century 
The Industrial Revolution 
Modern Medicine 
Fertility rates & reduction 
Environmental pressures of 
urbanization from population 
growth are reduced because birth 
rates in urban areas usually are 3-
4 X’s lower than in rural areas. 
Cities provide education 
opportunities. 
Some countries, including China, penalize 
couples who have more than one or two 
children by: 
1. Raising their taxes 
2. Charging other fees 
3. Eliminating income tax deductions for a 
couple’s third child 
4. Loss of health-care benefits, food allotments 
and job options 
In China couples who pledge to have no more than 
one child receive 
1. Extra food 
2. Larger pensions 
3. Better housing 
4. Free medical care 
5. Salary bonuses 
6. Free school tuition for their one child 
7. Preferential treatment in employment when their 
child enters the job market. 
However, according to some studies, 
there is a strong preference for male 
children. 
1. Girls are aborted at a higher rate than 
boys 
2. Some infant girls are killed 
3. Male children sometimes are fed better 
than female children. 
SOLUTIONS: INFLUENCING 
POPULATION SIZE 
Family planning has been a major factor 
in reducing the number of births and 
abortions throughout most of the world. 
Women tend to have fewer children if 
they are: 
Educated. 
Hold a paying job outside the home. 
Do not have their human right suppressed. 
SOLUTIONS: INFLUENCING 
POPULATION SIZE 
The best way to slow population growth 
is a combination of: 
Investing in family planning. 
Reducing poverty. 
Elevating the status of women. 
Factors that affect birth & fertility rates 
Importance of kids 
in labor force 
Urbanization 
Cost of raising & 
educating kids 
Availability of private 
& public pensions 
Religious beliefs, 
traditions & cultural 
norms 
Educational & 
employment 
opportunities 
Infant mortality rate 
Average age at 
marriage 
Availability of 
reliable birth control 
1994 Global Summit on 
Population & Development 
Cairo, Egypt 
Encouraged action to stabilized the 
world’s population at 7.8 billion by 
2050, instead of the projected 11-
12.5 billion. 
The major goals are to: 
Provide universal access to family-planning 
services. 
Improve the health care of infants, children & 
pregnant women 
Encourage development of national population 
policies 
Improving the status of women by expanding 
education & job opportunities 
Major goals continued: 
Increase access to education for girls 
Increase men’s involvement in child-
rearing responsibility & family planning 
Take steps to eradicate poverty 
Reduce & eliminate unsustainable 
patterns of production & consumption. 
Annual Rate of Natural Population 
Change (%)= 
Birth rate – Death rate 
 1,000 people x 100 
Declining Fertility Rates: 
Fewer Babies per Women 
The replacement level to sustain a population 
is 2.0 children. 
In 2006, the average global Total Fertility 
Rate was 2.7 children per woman. 
1.6 in developed countries (down from 2.5 in 
1950). 
3.0 in developing countries (down from 6.5 in 
1950).