Transcript Population - yayscienceclass

World Population Log
http://www.census.gov/ipc/www/popclockworld.html
Date: 11/02/2010
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Bellwork Question
Your parents give you two options for allowance
1. 1,000 a month
2. 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 the
month under option 2?
Which option do you choose?
.01
.02
.04
2.56
5.12
10.24
1310.72
.16
.32
.64
1.28
20.48
40.96
81.92
163.84
327.68
655.36
209711.52
41943.04
83886.08
2621.44
5242.88
10,485.76
167772.16
2684354.56
671088.64
335544.32
.08
1342177.28
5368709.12
10,737,418.24
Over 10 million!!
Question
•
Which type of population exhibits this sort of
growth?
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.
Accelerated World Population Growth
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)
A Brief History of Human
Population Growth
1.
Hunters and gatherers
•
2.
The world’s population was probably less
than a few million
Early, pre-industrial agriculture
•
•
3.
Allowed a much greater density of people
The first major increase in human population
Machine age
•
4.
Industrial revolution led to rapid increase in human population
The Modern era
•
Rate of population has slowed in wealthy nations but
continues to increase rapidly in poorer, less developed
nations.
© 2008 John Wiley and Sons Publishers
© 2008 John Wiley and Sons Publishers
© 2008 John Wiley and Sons Publishers
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!
Doubling Time Changes with Changes in Growth Rate
Because the world’s population rate is increasing at a rate between 12% we can expect the world’s population to DOUBLE within the next 35
to 70 years.
QUESTIONS:
•
Look at the graph on the left.
As growth rate increases
what happens to doubling
time?
© 2008 John Wiley and Sons Publishers
•
Why is this a problem?
•
Do you remember the
formula to calculate doubling
time? If you have forgotten
check page 58.
© 2008 John Wiley and Sons Publishers
United States Population 1790-2000
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?
© 2008 John Wiley and Sons Publishers
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?
A
– Why might that be?
•
Which age structure
diagrams have more men
than women at age 80+
– Why might that be?
•
B
Which age structure diagram
has the fewest elderly
people?
– Why might that be?
C
© 2008 John Wiley and Sons Publishers
Population Growth Rates
(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…
Rates continued…
increase population
births

immigration 
decrease population
 deaths
 emigration (exit)
r = (birth - death)+ (immigration-emigration)
immigration = migration of individuals into a population
from another area or country
emigration = migration of individuals from a population
bound for another country
Growth Rate Example
r = (b - d)+ (i - e)
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.
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
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
• 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=PxI
• T=total impact
• P= population size
• I=average environmental impact per person
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 disease
 Appears 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 population
 Typically occurs in a relatively small but relatively
constant presentation of the population
 Examples include heart disease, cancer, and stroke
Human Death Rates and the Rise of
Industrial Societies
Image © 2008 John Wiley and Sons Publishers
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:
1400
1200
1000
800
600
400
200
0
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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
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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
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•
•
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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.
Thomas Malthus vs The Marquis de Condorcet
• Malthus: Population will outgrow food
supplies (geometric growth vs
arithmetic growth)
http://cepa.newschool.edu/het/profiles/malthus.htm
• Condorcet: Reasoned human action
will reduce population, reduce waste,
and maintain food supply
http://cepa.newschool.edu/het/profiles/condorcet.htm
Paul Ehrlich vs Julian Simon
• Ehrlich: Population is outgrowing
earth’s sustainable capacity
• Simon: Population growth not
problem, but contributes to
economic development; Need for
Individual Economic Freedom
http://www3.interscience.wiley.com:8100/legacy/college/botkin/0471389145/ed/pa03.html
Population Problems
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Poverty
Food Problems
Standard of Living
Environmental Consequences of Consumption
Overcrowding
Population Growth: Solutions
• 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