Chapter 9
The Human Population
Chapter 9 Big Idea
• The size and growth rate of human
population has changed drastically over the
last 200 years. Those changes have led to
profound changes to almost every place on
Earth.
JQ: If 2.4 humans are born every
second, then how many are born each
day?
207,360 people born each day
This is AFTER we factor in
deaths
over 75,000,000 people born each year
JQ: Which of the following graphs do you
think represents the world’s population
growth over the next few hundred years
(population in vs. time)? Explain.
-or-
Section 1: Studying Human Populations
• Describe how the size and growth rate for human
population has changed over history
• What factors lead to population changes
• Analyze populations using Age Structure Diagrams
• Define demographic transition
• Describe what you see on this graph
•How long did it take to get to 1 billion, than 2,
3,4,5,6
Did You Know? Basic sanitation was rare even in the medical profession
•How
many
people
are living discovered
today? that doctors’ hand
until
1861,
when Dr.
Ignaz Semmelweis
washing greatly reduced patient mortality.
•Why did it take so long to reach 1 billion?
•Why do you think it took off around the late 1880s?
Interesting Fact: Of all the humans ever born,
approximately 6-7% are alive today.
• Rapid population growth has led to serious
environmental problems
Studying Human Populations
• Demography: the study
of human population
• How many people live
where?
• How long are you expected
to live?
• How many children are you
likely to have.
2 General Categories of Populations
• Developed Countries
–
–
–
–
Higher average income
Slower population growth
Diverse industrial economies
Stronger social support
systems
• Developing Countries
– Lower average incomes
– Rapid population growth
– Simple, agriculture-based
economies
Exponential Growth
Exponential Growth: rapid growth often seen
as J-Shaped curve on a graph
Is exponential growth sustainable?
Forecasting Population Size
• Will new schools be
needed?
• Should we be building
more housing?
• Should farming practices
be improved?
• Predictions like this often
wrong because human
behavior changes
POPULATION SIZE
http://www.worldometers.info/worl
d-population/
Forecasting Population Size
• Age Structure: the
distribution of ages in a
population
• Age Structure Diagrams
aka Population Pyramids
• What is useful about
these diagrams?
•What do age structure diagrams show?
•What are the “reproductive years”?
•Why is that important in forecasting future
population growth?
•Which “type” of countries are going to see
most of the population growth?
•Which “type” of countries do people live
longer lives?
Population Age Structure
Male
Female
Rapid Growth
Guatemala
Nigeria
Saudi Arabia
Ages 0-14
Slow Growth
United States
Australia
Canada
Ages 15-44
Zero Growth
Spain
Austria
Greece
Negative Growth
Germany
Bulgaria
Sweden
Ages 45-85+
Fig. 10-14 p. 184
Forecasting Population Size
•Survivorship: percent of population likely to
survive to any given age
•Survivorship Curves – show how much of
the population survives for a given age
•Type I
•Wealthy, developed countries
•Most people live to be very old
•Type II
•Similar death rates at all ages
•Type III
•Very poor, undeveloped countries
•Many children die
Survivorship
• Individuals of different
ages have different
probabilities of dying
• Survivorship curves
show how the
likelihood of death
varies with age.
Type I survivorship
curves are for
species that have a
high survival rate of
the young, live out
most of their
expected life span
and die in old age.
Humans are a good
example of a
species with a Type
I survivorship curve
Type II survivorship curves are for species that have a relatively
constant death rate throughout their life span. Death could be
due to hunting or diseases. Examples of species exhibiting a Type
II survivorship curve are coral, squirrels, honey bees and many
reptiles.
Type III
survivorship
curves are found
in species that
have many young,
most of which die
very early in their
life. Plants,
oysters and sea
urchins are
examples of
species that have
Type III
survivorship
curves.
If a tree wants to successfully reproduce, how many
seeds should it spread?
If a couple in India knows for sure there child will
survive to adulthood, will they decide to have more or
less children do you think?
PROJECTED WORLD POPULATIONS
What causes population to rise?
Population
Changes =
(births + immigration) – (deaths + emigration)
For world population growth we are only
concerned about births and deaths.
Many developed countries would have
negative population growth without
immigration.
Population
Change = (births + immigration) – (deaths + emigration)
• Migration: movement
INTO (immigration) or OUT
of (emigration) an area
U.S. growth
continues
because of both
births and
immigration
Population
Change = (births + immigration) – (deaths + emigration)
• Death rates on the
decline… people living
longer
• Why?
Better hygiene,
sewage disposal,
clean water,
medicines,
education, access to
food, nutrition
Life Expectancy
• Life Expectancy:
average number of
years members of a
population are
expected to live
• Improvement in most
of world
• Lower INFANT
MORTALITY
Compared to our neighbors
Major changes in U.S. over last 100+ years
Fertility Rates
• Fertility Rate:
number of
children born each
year per 1,000
women
• Total fertility rate
(lifetime)
• Replacement level
•
What does this graph show?
•Total Fertility Rate – average number of births in one woman’s
lifetime
• How have U.S. fertility rates changed?
Fertility and Women
• Two main factors impact
fertility rates worldwide
• Education level of women
(knowledge of family
planning)
• Economic level of women
• Generally :
more education = more wealth = lower fertility rates
Demographic Transition
Every Country Goes Through It
A model that describes how economic &
social changes affect population growth
rates
Demographic Transition
Every Country Goes Through It
Explain what you see on this chart
• Stage 1 : High Birth AND Death rates = little population change
• Stage 2 : Death Rates Fall, Birth Rates Still High = Population Growth
• Stage 3: Death Rates Low, Birth Rates Drop = Population Growth Slows
• Stage 4: Death Rates Low, Birth Rate Low = Population Declines
DESCRIBE EACH STAGE: WHAT DO YOU SEE?
Calculations
• A town currently has a population of 20
people. If 10 people are born, 8 people die, 3
immigrate and 1 emigrate, what is the
population?
Calculations
• USA currently has a population of 320,000,000
people. If 5,000,000 people are born,
2,000,000 people die, 200,000 immigrate and
50,000 emigrate, what is the population?
JQ: The current US population is
307,000,000 How long do think that it
will take America’s population to
double?
Rule of 70: Doubling Time
• Currently, a city has a population of 10 million. If the
population is growing at 10%, when will it reach 20
million? (70/rate = doubling time)
• What is the growth rate if the population increases from
200 million to 400 million in 14 years ?
(70/doubling
time = rate)
Section 1 Review
• Describe how the size and growth rate for human
population has changed over history
• What factors lead to population changes
• Analyze populations using Age Structure Diagrams
• Terms: Demography, Age Structure, Survivorship,
Fertility, Migration, Life Expectancy
China’s One-Child Policy
• In 1970, the average Chinese woman had about six
children.
• Since 1979, China has used a system of rewards and
punishments to enforce a one-child limit to slow
population growth.
• In 2005, there were 32 million more males than
females in China under the age of 20
Talk About It - Is it ethical for
governments to limit or
encourage human population
growth?
Section 2 : Population Trends
• What are the problems associated with rapid
human population growth?
• Compare developed and developing (less
developed) countries
• Investigate strategies for reducing population
growth
Problems With Rapid Growth
Lack of infrastructure to
support population
• Water supplies
• Sewers
• Roads
• Schools
• Power Plants
• Hospitals
• Housing
Problems With Rapid Growth
Using up resources too
quickly
• Water supplies
• Vegetation
– Food supplies
– Wood/fuels : wood
supplies critical to life in
many regions
• Land
Problems With Rapid Growth
Shortage of Fuel Wood
• Supply of fuel ensures
– Boiled water
– Cooked food
Problems With Rapid Growth
Unsafe water supplies
• Sewage mixing with
water supplies
– Cholera
– Dysentery
– Typhoid
• 1 billion lack clean
water
• 3 million/yr die
Clean Water Lacking
If the millions of women who haul water long distances had a
faucet by their door, whole societies could be transformed.
Problems With Rapid Growth
Land becomes scarce
• Arable land : land that
can grow crops
• Trade-offs made:
– agriculture, housing,
natural habitats
• Which do you think
typically wins out?
Problems With Rapid Growth
Urbanization: movement
of people from rural
areas to cities
• Much of world is going
through
• Increased demand on
infrastructure
Problems With Growth
In U.S.
Suburban sprawl: work in
cities live in suburbs
– Decay of inner cities
– Increased traffic
– Loss of farmland
– Decreased wildlife
habitat
Suburban Sprawl
Diverse World Population
Developed Countries
US, Canada, Japan,
Australia, New
Zealand and most of
Europe. High Per
Capita GDP. (1.2
billion people)
Comparing a Developed Country
to a
Moderately Developed
to a
Developing (Least Developed)
Diverse World Population
• Developing (lesser
developed)
• 5.2 billion people
• living with very little
• 97% of population
growth
Percent of
World’s
19
Population
81
Population
growth
0.1
1.6
85
Wealth and
income
Resource
use
15
88
12
75
Pollution
and waste
25
Developed
countries
Developing
countries
World Growth Rates
Strategies for Controlling Growth
•
•
•
•
•
Public Advertisements
Economic Incentives
Legal Punishments
Empowering Women
Investments in
Education and Family
Planning
Worldwide fertility rates are dropping
Growth Is Slowing but still growing
Medium growth rate – fertility rates decline to replacement level by 2050
Section 2 Review
• What are problems associated with rapid
human population growth?
• How do developed and developing (less
developed) countries compare?
• What are some strategies for reducing
population growth?