Chapter 9The 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

over 75,000,000 people born each year

This is AFTER we factor in deaths

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

• How many people are living today?Did You Know? Basic sanitation was rare even in the medical profession until 1861, when Dr. Ignaz Semmelweis discovered that doctors’ hand 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/world-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?

Ages 0-14Ages 0-14 Ages 15-44Ages 15-44 Ages 45-85+Ages 45-85+

Rapid GrowthGuatemala

NigeriaSaudi Arabia

Rapid GrowthGuatemala

NigeriaSaudi Arabia

Slow GrowthUnited States

AustraliaCanada

Slow GrowthUnited States

AustraliaCanada

MaleMale FemaleFemale

Zero GrowthSpainAustriaGreece

Zero GrowthSpainAustriaGreece

Negative GrowthGermanyBulgariaSweden

Negative GrowthGermanyBulgariaSweden

Population Age StructurePopulation Age Structure

Fig. 10-14 p. 184Fig. 10-14 p. 184

• 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

Forecasting Population Size

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.

• Migration: movement INTO (immigration) or OUT of (emigration) an area

Population

Change = (births + immigration) – (deaths + emigration)

U.S. growth continues because of both births and immigration

• Death rates on the decline… people living longer

• Why?

Population

Change = (births + immigration) – (deaths + emigration)

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 TransitionEvery Country Goes Through It

A model that describes how economic & social changes affect population growth rates

Demographic TransitionEvery 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 GrowthIn 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 CountriesUS, 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

Developingcountries

Developedcountries

Population

Populationgrowth

Wealth andincome

Resourceuse

Pollutionand waste

19

81

0.1

1.6

85

15

88

12

75

25

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?