world population log date: 11/02/2010 population: date:

World Population Loghttp://www.census.gov/ipc/www/popclockworld.html

Date: 11/02/2010 Population:Date: Population:Date: Population:Date: Population:Date: Population:Date: Population:Date: Population:Date: Population:Date: Population:

Bellwork QuestionYour parents give you two options for allowance

1. 1,000 a month2. A penny on the first day of the month that doubles to two

pennies on the second day and so on until the last day of the month

How much money do you have at the end of themonth under option 2?

Which option do you choose?

.01 .02 .04 .08

.16 .32 .64 1.28 2.56 5.12 10.24

20.48 40.96 81.92 163.84 327.68 655.36 1310.72

2621.44 5242.88 10,485.76 209711.52 41943.04 83886.08 167772.16

335544.32

671088.64

1342177.28

2684354.56

5368709.12 10,737,418.24

Over 10 million!!

Question• Which type of population exhibits this sort of

growth?

PART

A

Chapter 4

The Human Population and

the Environment

Basic Concepts of Population Dynamics

• Population:– A group of individuals of the same species

living in the same area, at the same time.

• Species:– All individuals that are capable of

interbreeding & producing fertile offspring.

• Population dynamics– The general study of population changes.

First Billion: 1804

Second Billion: 1927 (123 yrs)

Third Billion: 1960 (33 yrs)

Fourth Billion: 1974 (14 yrs)

Fifth Billion: 1987 (13 yrs)

Sixth Billion: 1999 (11 yrs)

Accelerated World Population Growth

A Brief History of Human Population Growth

1. Hunters and gatherers• The world’s population was probably less

than a few million

2. Early, pre-industrial agriculture• Allowed a much greater density of people• The first major increase in human population

3. Machine age• Industrial revolution led to rapid increase in human population

4. The Modern era• Rate of population has slowed in wealthy nations but

continues to increase rapidly in poorer, less developed nations.

Disparities

• Developed countries– 15% of the world’s population– Control 80% of the world’s wealth

• Low-income developing countries– 37% of the world’s population– Control 3.0% of the world’s gross national

income

• Difference in per capita income: 63 to 1!


Because the world’s population rate is increasing at a rate between 1-2% we can expect the world’s population to DOUBLE within the next 35 to 70 years.

Doubling Time Changes with Changes in Growth Rate

QUESTIONS:• Look at the graph on the left.

As growth rate increases what happens to doubling time?

• Why is this a problem?

• Do you remember the formula to calculate doubling time? If you have forgotten check page 58.


QUESTIONS:• The growth rate in the United

States is slowing. So why then is the global population continuing to rise?

• What can be done about it?

United States Population 1790-2000

90% of population growth is happening in Third World

Age Structure

• Population age structure:– The proportion of the population in each age

class– Affects current and future birth rates, death

rates and growth rates– Has an impact on the environment– Has complications for current and future

social and economic status.

• Which age structure diagram has the most young people?

– Why might that be?

• Which age structure diagrams have more men than women at age 80+


• Which age structure diagram has the fewest elderly people?


A

B

C

(b) crude birth rate= number birth per 1000 individuals(d) crude death rate= number death per 1000 individuals(r) growth rate = natural increase in population expressed as percent per years (If this number is negative, the population is shrinking.) equation:

r = b – d

But other factors affect population growth in a certain area…

Population Growth Rates

Rates continued…increase population decrease population births deathsimmigration emigration (exit)

r = (birth - death)+ (immigration-emigration)immigration = migration of individuals into a population from another area or countryemigration = migration of individuals from a population bound for another country

r = (b - d)+ (i - e)

B D I E r=( 10/1000) – (5/1000) + (1/1000) – (10/1000) r=(0.01-0.005) + (0.001 – 0.01)r = 0.005 – 0.009 = -0.004 or –0.4% per year

example: population of 10,000 has 100 births (10 per 1000)50 deaths (5 per 1000)10 immigration (1 per 1000)100 emigration (10 per 1000)

You try.

Growth Rate Example

Projecting Future Population Growth

• Exponential growth and doubling time• The logistic growth curve

– “S” shaped curve that is generated by the logistic growth equation.

• A small population grows rapidly• But the growth rate slows down• The population eventually reaches a constant size.

• Logistic carrying capacity– The population size at which births equal deaths and

there is no net change in population

Forecasting Population Change

• Formula to represent population change:

P2 = P1 + (B – D) + (I – E)

P1 = number of individuals in a population at time 1

P2 = number of individuals in a population at time 2 (time 2 = a later time)

The Demographic Transition

Demographic transition:– Three-stage pattern of change in birth rates and death

rates.– Occurred during the process of industrial and economic

development of Western nations.– Leads to a decline in population growth.

Stage I: Decline in death rate

Stage II: High growth rate

Stage III: Birth rate drops toward the death rate, leading to low or zero growth rate.

Population and Technology

• T=total impact• P= population size• I=average environmental impact per person

• The total impact of the human population on the environment is:– the average impact of an individual multiplied

by the total number of individuals

T = P x I

The Human Population, the Quality of Life, and the Human Carrying

Capacity• Human carrying capacity

– The number of people that can live on Earth at the same time?

– To determine:

1. Extrapolate from past growth

2. The “Packing Problem” approach– Considers how many people might be packed onto Earth,

not taking into sufficient account the need for lands and oceans to provide food, water, energy, construction materials, and scenic beauty and the need to maintain biological diversity

Human Death Rates and the Rise of Industrial Societies

Acute or epidemic diseaseAppears rapidly in the population,Affects a comparatively large percentage of it,Declines then almost disappears, only to reappear

later

Chronic disease Is always present in a populationTypically occurs in a relatively small but relatively

constant presentation of the populationExamples include heart disease, cancer, and stroke

Image ©

2008 John Wiley and S

ons Publishers

Human Death Rates and the Rise of Industrial Societies

Differences between Chronic & Acute (Epidemic) Illnesses

Longevity and its Effect on Population Growth

• Maximum lifetime:– The genetically determined

maximum possible age to which an individual of a species can live

• Life expectancy:– The average number of years an individual

can expect to live given the individual’s present age

Carrying Capacity• The environment has a CARRYING

CAPACITY for each population…– Carrying capacity is the number of

organisms that an environment can support.

• Once a population reaches its capacity, its growth stops.

Question

• What are some examples of things that can limit growth?

What can limit growth?• Limiting factors limit growth

– Different sizes of populations will also have different factors affecting them.

• When growth has been limited its graph will look like this:

0

200

400

600

800

1000

1200

1400

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

Growth Curves

Limiting Factors

1. Short-term factors• Those that affect a population

during the year in which they become limiting

2. Intermediate-term factors• Those whose effects are

apparent after one year but before ten years

3. Long-term factors• Those whose effects are not

apparent for ten years

Some factors fit into more than one category

Density Dependent & Density Independent Factors

1. Density Dependant Factors are factors that have an increasing effect as the population increase, hence will affect larger populations. – Examples: Disease, Competition, Parasites, Predators, Food

– These types of factors spread faster in larger populations.

2. Density Independent Factors effect any population, regardless of size. Population size does not matter.– Examples: Volcanic eruption, Temperature, Storms, Floods, drought,

chemical pesticides

How Can We Achieve Zero Population Growth?

• Delay the age of first childbearing by women• Birth control

– Biological and Social• Breast-feeding, which can delay resumption of ovulation• Abstinence• Induction of sterility with natural agents• Contraceptive devices

– National Programs to Reduce Birth Rates• Formal family planning programs to

– explain the problems arising from rapid population growth– Describe the benefits to individuals of reduced population

growth.

• Malthus: Population will outgrow food supplies (geometric growth vs arithmetic growth)

• Condorcet: Reasoned human action will reduce population, reduce waste, and maintain food supply

Thomas Malthus vs The Marquis de Condorcet

http://cepa.newschool.edu/het/profiles/condorcet.htm

http://cepa.newschool.edu/het/profiles/malthus.htm

• Ehrlich: Population is outgrowing earth’s sustainable capacity

• Simon: Population growth not problem, but contributes to economic development; Need for Individual Economic Freedom

Paul Ehrlich vs Julian Simon

http://www3.interscience.wiley.com:8100/legacy/college/botkin/0471389145/ed/pa03.html

• Poverty • Food Problems • Standard of Living • Environmental Consequences of Consumption • Overcrowding

Population Problems

• Override – forced government programs to reduce population

• Collaboration – voluntary programs and incentive based family

planning programs• Economic Development

– higher GNP per capita• Social Development

– better education, health facilities, gender equity • Family Planning Programs

– sterilization, promotion of contraceptive use

Population Growth: Solutions

world population log date: 11/02/2010 population: date:

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