Population Dynamics
Population Dynamics
Warm Up: Identify and describe three
negative consequences of the practice
of factory farming of chicken, cows, and
pigs.
Give one social and one economic
advantage.
Populations
‣ Organisms do not generally
live alone. A population is a
group of organisms from
the same species
occupying in the same
geographical area.
‣ This area may be difficult to
define because:
A population may
comprise widely dispersed
individuals which come
together only infrequently,
e.g. for mating.
Populations may fluctuate
considerably over time.
Migrating wildebeest population
Tiger populations comprise widely
separated individuals
Features of Populations
‣ Populations are dynamic
and exhibit attributes that
are not shown by the
individuals themselves.
‣ These attributes can be
measured or calculated and
include:
Population size: the total
number of organisms in
the population.
Population density: the
number of organisms per
unit area.
Population distribution:
the location of individuals
within a specific area.
Features of Populations
‣ Population composition
provides information
relevant to the dynamics of
the population, i.e. whether
the population is increasing
or declining.
‣ Information on population
composition (or structure)
includes:
Sex ratios: the number of
organisms of each sex.
Fecundity (fertility): the
reproductive capacity of
the females.
Age structure: the
number of organisms of
different ages.
Population Dynamics
• The study of changes in the
size and composition of
populations, and the factors
influencing these changes, is
population dynamics.
• Key factors for study include:
Population growth rate: the
change in the total population
size per unit time.
Natality (birth rate): the
number of individuals born per
unit time.
Mortality (death rate): the
number of individuals dying
per unit time.
Migration: the number
moving into or out of the
population.
Population size is influenced by births…
…and deaths
Migration
• Migration is the
movement of organisms
into (immigration) and out
of (emigration) a
population. It affects
population attributes such
as age and sex structure,
as well as the dynamics
of a population.
Populations lose
individuals through
deaths and emigration.
Populations gain
individuals through births
and immigration.
Net Migration =
Immigration - Emigration
Wildebeest - land based migration
Canada geese - aerial migration
Migrating species may group together to
form large mobile populations
Population Density
• The number of individuals
per unit area (for terrestrial
organisms) or volume (for
aquatic organisms) is
termed the population
density.
At low population densities,
individuals are spaced well
apart. Examples: territorial,
solitary mammalian
species such as tigers and
plant species in marginal
environments.
At high population
densities, individuals are
crowded together.
Examples: colonial
animals, such as rabbits,
corals, and termites.
Low density populations
High density populations
Population Distribution
• A crude measure of population
Clumped distribution in termites
More uniform distribution in cacti
density tells us nothing about
the spatial distribution of
individuals in the habitat.
• The population distribution
describes the location of
individuals within an area.
Distribution patterns are
determined by the habitat
patchiness (distribution of
resources) and features of the
organisms themselves, such
as territoriality in animals or
autotoxicity in plants.
Individuals in a population
may be distributed randomly,
uniformly, or in clumps.
Random Distribution
• A population’s distribution is
considered random if the
position of each individual is
independent of the others.
• Random distributions are not
common; they can occur only
where:
The environment is uniform and
resources are equally available
throughout the year.
There are no interactions
between individuals or
interactions produce no
patterns of avoidance or
attraction.
• Random distributions are seen in
some invertebrate populations,
e.g. spiders and clams, and
some trees.
Spider populations appear to show a
random distribution
Uniform Distribution
• Uniform or regular distribution
patterns occur where individuals
are more evenly spaced than
would occur by chance.
• Regular patterns of distribution
result from intraspecific
competition amongst members
of a population:
Territoriality in a relatively
homogeneous environment.
Competition for root and crown
space in forest trees or
moisture in desert and savanna
plants.
Autotoxicity: chemical inhibition
of plant seedlings of the same
species.
Saguaro cacti compete for moisture and
show a uniform distribution
Clumped Distribution
• Clumped distributions are the
most common in nature;
individuals are clustered together
in groups.
• Population clusters may occur
around a a resource such as
food or shelter.
• Clumped distributions result from
the responses of plants and
animals to:
Habitat differences
Daily and seasonal changes in
weather and environment
Reproductive patterns
Social behavior
Sociality leads to clumped distribution
Density Dependent Factors
• Density dependent factors
exert a greater effect on
population growth at higher
population densities.
At high densities, individuals:
Compete more for
resources.
Are more easily located by
predators and parasites.
Are more vulnerable to
infection and disease.
Competition increases in
crowded populations
• Density dependent factors
are biotic factors such as
food supply, disease,
parasite infestation,
competition, and predation.
Parasites can spread rapidly
through dense populations
Species Interactions
‣ No organism exists in isolation. Each participates in
interactions with other organisms and with the abiotic
components of the environment.
‣ Species interactions may involve only occasional or
indirect contact (predation or competition) or they may
involve a close association between species. Symbiosis
is a term that encompasses a variety of such close
associations, including parasitism (a form of
exploitation), mutualism, and commensalism.
Canopy tree with symbionts attached
Oxpecker birds on buffalo
Parasitism
‣ Many animals have
representatives that have
adopted a parasitic lifestyle.
‣ Parasites occur more
commonly in some species
than in others. Insects, some
annelids, and flatworms have
many parasitic representatives.
‣ Parasites live in or on a host
organism. The host is always
harmed by the presence of the
parasite, but it is not usually
killed. Both parasite and host
show adaptations to the
relationship.
‣ Parasites may live externally on
a host as ecto, or within the
host’s body as endoparasites.
Tick ectoparasite on bird wing
Many mammals use dust bathing to rid
themselves of external parasites
Ectoparasites
• Ectoparasites, such as ticks, mites,
lice, bed bugs, and fleas, live
attached to the outside of the host,
where they suck body fluids, cause
irritation, and may act as vectors for
pathogens or disease-causing
agents.
‣ Insect vectors include human lice, rat
fleas, mosquitoes and tsetse flies.
Bed bug (Cimex lectularis)
Human flea (Pulex irritans)
Mosquito vector for Dengue fever (Aedes albopictus)
Head louse (Pediculus humanus)
Endoparasites
‣ In many endoparasites, a
primary host (in which the
parasite becomes sexually
mature) and one or more
intermediate hosts (which
usually house larval stages)
are required to complete the
life cycle.
‣ Endoparasitic species such as
the pork tapeworm, Taenia
solium, are highly specialized
to exploit the resources of the
host.
Adaptations, such as
specialized mouthparts and
lack of a digestive tract,
enable them to spend their life
inside the intestines of their
vertebrate hosts.
Taenia scolex
(head region)
Taenia proglottid
(reproductive segment)
Horse gut nematode
Sheep liver fluke
Plant Parasites
‣ A great diversity of plant parasites
exist. Some depend only partly on
their host plant for nutrition; they
are photosynthetic but utilize the
host’s nutrients, e.g. mistletoe.
‣ Others are entirely parasitic and are
unable to photosynthesize, e.g.
cancer root (Conopholis americana)
dodder, and wood rose
(Dactylanthus taylorii).
Cancer root (top) and wood rose
are holoparasitic and dependent
entirely on the host plant.
Mistletoe Phoradendren spp. are hemiparasites;
photosynthesizing but lack their own roots and
rob their host plant of water and nutrients.
Mutualistic Relationships
‣ In mutualistic relationships
both species benefit. This
occur between some birds
(such as oxpeckers) and
large herbivores (such as
zebra, Cape buffalo, and
rhinoceros). The herbivore is
cleaned of parasites and the
oxpecker gains access to
food.
‣ Lichens show an obligate
mutualism between a fungus
and either a green algae or a
cynobacterium. The fungus
obtains organic carbon from
the algae. The algae obtains
water and nutrient salts from
the fungus.
Cape buffalo and oxpecker birds
Lichen: an obligate mutualism
Commensal Relationships
• In commensal relationships,
one party (the commensal)
benefits, while the host is
unaffected.
‣ Epiphytes (perching plants)
gain access to a better
position in the forest canopy,
with more light for
photosynthesis, but do no
harm to the host tree.
‣ Commensal anemone
shrimps (Periclimenes spp.)
live within the tentacles of
host sea anemones. The
shrimp gains protection from
predators, but the anemone is
neither harmed nor benefitted.
Exploitation
• Exploitation describes
relationships where one
species benefits at the
expense of another. It
includes several familiar
interactions:
Predation: Predator kills
the prey outright, e.g. lions
hunting zebra.
Herbivory: The herbivore
feeds on, but usually does
not kill, the plant, e.g. zebra
grazing on grass.
Parasitism: The parasite
does not usually kill its host,
e.g. ticks feeding on the
blood of a zebra.
Types of Interaction
Density Independent Factors
• The effect of density
independent factors on a
population’s growth is not
dependent on that population’s
density:
Physical (or abiotic) factors
temperature
precipitation
humidity
acidity
salinity etc.
Catastrophic events
floods and tsunamis
fire
drought
earthquake and eruption
Population Growth
• Population growth depends on the
number of individuals added to the
population from births and
immigration, minus the number lost
through deaths and emigration.
‣ This can be expressed as a
formula:
Population growth =
(Births – Deaths) + (Immigration – Emigration)
(B)
(D)
(I)
(E)
• Net migration is the difference
between immigration and
emigration.
Calculating Population Change
Births, deaths, and net migrations
determine the numbers of
individuals in a population
Rates of Population Change
‣ Ecologists usually measure
the rate of population
change. These rates are
influenced by
environmental factors and
by the characteristics of the
organisms themselves.
‣ Rates are expressed as:
Numbers per unit time,
e.g. 2000 live births per
year
Per capita rate number
per head of population.
Crude rate per 1000
persons
e.g. 122 live births per
1000 individuals (12.2%)
Many invertebrate populations
increase rapidly in the right conditions
Large mammalian carnivores have
a lower innate capacity for increase
Exponential Growth
‣ Populations becoming
Colonizing Population
They may undergo a rapid
exponential (logarithmic)
increase in numbers to
produce a J-shaped growth
curve.
‣ In natural populations,
population growth rarely
continues to increase at an
exponential rate.
‣ Factors in the environment,
such as available food or
space, act to slow population
growth.
Population numbers (N)
established in a new area for
the first time are often termed
colonizing populations.
Here the number
being added to the
population per unit
time is large.
Exponential (J) curve
Exponential growth
is sustained only
when there are no
constraints from the
environment.
Here, the number
being added to the
population per unit
time is small.
Lag
phase
Time
Logistic Growth Model
‣ As a population grows, its increase will slow, and it will
stabilize at a level that can supported by the
environment.
‣ This type of sigmoidal growth (S) produces the logistic
growth curve.
Population numbers (N)
The population encounters
resistance to exponential growth
as it begins to fill up the
environment. This is called
environmental resistance.
Established Population
Carrying capacity (K)
The maximum population density
that can be supported by the
environment on a long term basis.
Logistic (S) curve
As the population grows,
the rate of population
increase slows, reaching
an equilibrium level
around the carrying
capacity.
Lag phase
Environmental resistance
increases as the
population overshoots K.
Environmental
resistance decreases as
the population falls
below K.
In the early
phase, growth
is exponential
(or nearly so)
The population tends to fluctuate around an
'equilibrium level'. The fluctuations are caused
by variations in the birth rate and death rate as
a result of the population density exceeding of
falling below carrying capacity.
Time
Life Tables
‣ Numerical data collected during a population study can
be presented as a table of figures called a life table.
• Life tables provide a summary of mortality for a
population. The basic data are the number of individuals
surviving to each age interval. This gives the ages at
which most mortality occurs in a population.
Life table for a population of the barnacle Balanus
Age (yr)
No. alive at
the start of
the age
interval
Proportion of
original no.
surviving at the
start of the age
interval
No. dying
during the
age interval
Mortality
(d)
0
142
1.000
80
0.563
1
62
0.437
28
0.452
2
34
0.239
14
0.412
3
20
0.141
5
0.250
4
15
0.106
4
0.267
5
11
0.078
5
0.454
6
6
0.042
4
0.667
7
2
0.014
0
0.000
8
2
0.014
2
1.000
9
0
0.0
–
–
Survivorship Curves
• The age structure of a population can represented with a
survivorship curve. Survivorship curves use a semi-log plot of
the number of individuals surviving per 1000 in the population,
against age.
Because they are standardized (as number of survivors per
1000), species with different life expectancies can be easily
compared.
The shape of the curve reflects where heaviest mortality
occurs:
Type I: late loss
Number of
survivors (log
scale)
large mammals
Type II: constant loss
small mammals, songbirds
Type III: early loss
oysters, barnacles
Relative age
Type I Survivorship Curves
‣ Species with Type I or late
loss survivorship curves
show the heaviest mortality
late in life. Mortality is very
low in the juvenile years
and throughout most of
adult life.
Late loss curves are
typical of species that
produce few young and
care for them until they
reach reproductive age.
Such species are
sometimes called Kselected species and
include elephants,
humans, and other large
mammals.
Mortality is very
low in early life
Mortality increases
rapidly in old age
Type II Survivorship Curves
• Species with Type II or
constant loss survivorship
curves show a relatively
constant mortality at all life
stages.
Constant loss curves are
typical of species with
intermediate reproductive
strategies. Populations
face loss from predation
and starvation throughout
life.
Examples include some
many types of songbirds,
some annual plants, some
lizards, and many small
mammals.
Constant mortality.
No one age class is
any more susceptible
than any other.
Type III Survivorship Curves
• Species with Type III or early
loss survivorship curves
show the highest mortality in
early life stages, with low
mortality for those few
individuals reaching a
certain age and size.
Early loss curves are typical
of species that produce
large number of offspring
and lack parental care.
Such species are rselected species
(opportunists), and include
most annual plants, most
bony fish (although not
mouth brooders), and most
marine invertebrates.
Population losses are
high in early life stages
Mortality is low for
the few individuals
surviving to old age
‘r’ and ‘K’ Selection
‣ Two parameters govern
The intrinsic rate of
natural increase or biotic
potential. This is the
maximum reproductive
potential of an organism,
symbolized by the letter r.
The saturation density or
carrying capacity of the
environment, represented
by the letter, K.
‣ We can characterize
species by the relative
importance of r and K in
their life cycles.
Population numbers (N)
the logistic growth of
populations.
K-selected species
These species exist near
asymptotic density (K) for
most of the time. Competition
and effective use of resources
are important.
r-selected species
These species rarely reach
carrying capacity (K). Their
populations are in nearly
exponential growth phases for
much of the year. Early growth,
rapid development, and fast
population growth are important.
Time
K-Selected Species
‣ Species that are K-
selected exist under
strong competition and
are pushed to use
available resources more
efficiently.
These species have
fewer offspring and
longer lives.
They put their energy
into nurturing their
young to reproductive
age.
K-selected species
include most large
mammals, birds of prey,
and large, long-lived
plants.
Correlates of K-selected species
Climate
Fairly constant and/or
predictable
Mortality
Density-dependent
Survivorship
Usually types I and II
(late or constant loss)
Fairly constant in time.
Population size Near equilibrium with the
environment.
Competition
Usually keen.
Specialist niche.
Selection favors
Slower development,
larger body size, greater
competitive ability,
delayed reproduction,
repeated reproductions
Length of life
Longer (> one year)
Leads to:
Efficiency
r-Selected Species
‣ Species with a high intrinsic
capacity for population
increase are called rselected or opportunistic
species.
These species show
certain life history features
and, to survive, must
continually invade new
areas to compensate for
being displaced by more
competitive species.
Opportunists include
algae, bacteria, rodents,
many insects, and most
annual plants.
Correlates of r-selected species
Climate
Variable and/or
unpredictable
Mortality
Density-independent
Survivorship
Often type III
(early loss)
Population
size
Fluctuates wildly. Often
below K.
Competition
Variable, often lax.
Generalist niche.
Selection
favors
Rapid development, high
rm, early reproduction,
small body size, single
reproduction (annual)
Length of life
Short, usually less than
one year
Leads to:
Productivity
Population Dynamics
Population numbers (N)
Warm Up: Identify and describe three
key features of the logistic growth
model.
Time
Demography
‣ Demography is the study of human populations, their
characteristics and changes. Demographics will
measure:
Statistics about people, such as births, deaths, and
where they live as well as total population size.
Human Population Growth
‣ The world population, now over 7
billion, is growing at the rate of
about 80 million per year.
‣ Projections put the world population
at between 8 and 12 billion in 2050,
with nearly all of this growth
expected in the developing world.
Developing countries include:
Africa, Asia, Latin America, the
Caribbean, and regions of
Melanesia, Micronesia, and
Polynesia.
‣ 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.
Developed countries grew
at 0.1%
Developing countries grew
at 1.5% (15 times faster)
Growth Rate & Doubling Time
‣ Growth rate includes the birth rate,
death rate, immigration and
emigration. Usually calculated in
percent growth using the formula of
births minus deaths, plus immigration
minus emigration.
If a population of 10,000 experiences
100 births, 40 deaths, 10 immigrants and
30 emigrants in a year, what is the
annual percentage growth rate?
‣ Doubling time is the time (in years) it
takes for the population to double the
number of people in the current
population. Calculated as 70 / %
growth rate
If a population of a country grows at a
rate of 5% per year, the number of years
required for the population to double is
what?
Global Population Growth
‣ Estimates of likely future growth of the world human
population are highly uncertain and projections for
2050 range from a low of 7.7 billion to a high of 11.2
billion.
Global Human Population Growth
North America
High fertility rate: 11.2 billion
Medium fertility rate: 9.4 billion
Low fertility rate: 7.7 billion
Latin America & Caribbean
Europe
Asia & Oceania
Africa
Note: The latest
‘medium variant’ U.N.
projection of 9.37
billion is nearly 500
million (4.7%) lower
than the 9.83 billion
projected in 1994.
Demographic Transitions
‣ Demographic Transition describes the process where
countries become economically developed then their
birth and death rates begin to decline. In the past this
was referred to as “first” and “third” world countries or
“developed” and “developing”.
‣ Currently this process is described by the different
stages according to population growth:
Preindustrial stage shows little population growth due
to high birth rate with high death rate.
Transitional stage is where industrialization begins,
death rates drops and birth rates remain high. Rapid
population growth occurs.
Industrial stage is birth rate dropping and approaching
death rate. Population growth slowly declines.
Postindustrial stage are birth rate and death rate
become similar and population growth slows or declines.
Demographic Transition
‣ Generalized model of demographic transition shows that
the total fertility of a society decreases as the society
progresses through the demographic transition.
Some developing countries may have difficulty making the
demographic transition.
Demographic Transition
Age Structure
• Age structure refers to the
number of organisms of different
ages.
‣ Populations can be broadly
grouped into those individuals of:
pre-reproductive age
reproductive age
post reproductive age
‣ Analysis of the age structure of
populations can assist in their
management because it can
indicate where most population
mortality occurs and whether or
not reproductive individuals are
being replaced.
Size/age classes in fish
Human Age Structure
‣ Human age structure
varies from country to
country.
In developing
countries age
structure tends to be
in favor of younger
individuals with a
large proportion being
under 15 years.
In developed nations,
age structure is
relatively even
throughout the age
groups.
Age Structure in Human Populations
Determining Population Growth
‣ The rate at which a
population grows or declines
depends on its age
structure. Age structure
diagrams are a graphical
illustration that shows the
distribution of different age
groups. These groups are
further broken into cohorts:
Prereproductive age are
persons who are not mature
enough to reproduce
Reproductive age are those
persons that are capable of
reproduction.
Postreproductive age are
those persons too old to
reproduce.
Age Structure Diagrams
Age Structure
‣ Since age structure
diagrams are broken
down by age,
demographers can obtain:
Birth rate
Maturity rate
Death rate of an entire
population.
‣ These diagrams are
usually broken down by
country and divided into
genders.
32% of the people in
developing countries
were under 15 years old
in 2006 versus only 17%
in developed countries.
Age Structure: United States
‣ Monitoring the baby boom generation in yellow.
Rapid Growth Diagram
‣ Pyramid shaped histograms have a birth rate that exceeds the
‣
death rate. Lower cohorts have more males and females.
Population growth is rapid in countries that have a pyramid shape.
Current modern examples include Africa, Asia, and Latin America
Slow/Stable Growth Diagrams
‣ When the histogram shape is “box”-like, then stable or slow growth
‣
is represented.
Birth rate is almost equal to death rate.
Current examples of slow growth: USA, Australia, & Canada
Current examples of stable growth: Denmark, Austria, & Italy
Negative Growth Diagrams
‣ If there is declining or negative growth, then the birth rate with be
‣
less than the death rate.
Pyramids with declining populations tend to show larger numbers of
older persons in their population.
Current examples: Germany & Japan
Developing vs. Developed
‣ Developing (Transitional, Third World):
Higher infant mortality rate because of a shortage in prenatal
and pediatric care. Thus, they have more children to ensure
some survive.
Agricultural societies need children to help in the labor force.
Lower per capita income or poorer countries need children to
provide an income and sometimes contraceptives are not
affordable.
Women lack education and job opportunities.
‣ Developed (Industrial, First World):
Educated and working women tend to delay childbearing.
Pension systems support people as they age.
Family planning and the ability to control fertility.
Higher cost of raising children causes people to have smaller
families.
Population Dynamics
Warm Up: Identify and describe three
historical factors that have lead to
declining death rates.
http://apes.mcloda.com
http://semapes.wikispaces.com
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Homework: “Age Structure Diagrams”
Homework: “Population Calculations”
2000 #4 - Analyzing data (easy)
2003 #2 - Population growth and graph (hard)
2005 #2 - Demand for meat, calculations (medium)
2007 #4 – Urban vs Rural, Pollution (easy)
Urbanization
‣ Urbanization is the physical growth of urban
areas as a result of global change. As
agriculture and small-scale industry give
way to modern industry, resources are
drawn upon in an ever-widening area.
‣ As urbanization increases and natural
surfaces are covered or removed
decreasing transpiration, increasing runoff
and the groundwater supply is reduced due
to loss of recharge area.
Large amounts of energy are used and
waste is produced that need to be treated,
both municipal and sewage.
Concentration of people can cause pollution
and health problems.
Excessive noise pollution that can lead to
hearing loss and excessive light pollution
can cause plant and animal ecological
Las Vegas: 1973 (above) and 2006 (below)
Urbanization
‣ Urban sprawl removes trees and
vegetation which creates a heat-island
effect which explains that urban areas
trap more heat than rural areas
because of the heat generated by cars,
factories, furnaces, lights, air
conditioners, heat-absorbing dark
roofs, tall buildings and asphalt streets
in cities.
Increased combustion from
automobiles, airplanes and factories
has made for higher particulates, NOx,
SOx, lead, CO and smog. With less
vegetation there is also less filtering.
Industrial processes release
hydrocarbons & volatile fumes.
Most large cities have gone through
city planning to develop mass transit
systems and parks to help reduce
some of the pollution problems.
Central Park, New York City, NY
Urbanization
Urbanization is the movement of people from
rural areas into cities (Push / Pull)
Urban areas must import most of its food, water,
energy, minerals, & other resources because of
large populations
Large populations produce and consume
enormous quantities of resources that can pollute
the air, water & land.
Disease can easily spread in urban areas because
of the high density population.
Urbanization
Immigration Push
Factors
Rural overpopulation
Lack of food or work
Changing
agricultural practices
Desire for a better
education
Racial or religious
conflict
Political instability
Immigration Pull
Factors
Opportunity for better
jobs
Chance for better
housing
More reliable food
supply
Opportunity for greater
wealth
Freedom from village
traditions
Government policy
Mortality and Fertility
‣ Infant mortality rate: The number of child
and/or 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. This ensures care
for aging parents and a labor force.
Infant mortality rate is higher in
developing countries than in developed
countries.
Along with life expectancy, the infant
mortality rate is a good indicator of the
quality of life of a country
‣ Replacement-level fertility: the number
of children a couple must bear to replace
themselves.
Slightly higher than two children per
couple. (2.2 in developed countries and
Total Fertility Rates
‣ Total fertility rate (TFR): the average number of children a
woman has during reproductive years.
‣ 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).
‣ If fertility rate drops to replacement level fertility but the
population continues to grow, this is called population
momentum and can be seen in pyramid shaped age
structure diagrams.
‣ Birth rates and fertility rates have been slowed or
decreased because:
Cultural/religious practices prohibited birth control.
Cultural/religious practices favored large families.
Education/Employment/Status of women is low
Fertility Rates
‣ Based on current trends, it is assumed that human
fertility rates will continue to decline and life
expectancy will continue to increase. Developing
countries are expected to broadly follow these
demographic trends.
Trends in Fertility Rates
Africa
Asia
South & Central
America
Developed
Developing
Historical Factors
‣ Death rates have declined and
births have increased because:
The Green Revolution increased
food and water supplies and
productivity offering better
nutrition opportunities.
The Industrial Revolution
improved sanitation and allowed
improved personal hygiene
through safer water supplies.
Advances in medicine reduced
mortality rate. The improvement
in prenatal or neonatal care
greatly aided the decline in
death rate.
Fertilizers and pesticides
increased crop yields
More children live past
childbirth
Population Stabilization
‣ Human population growth is slower than predicted
but because of the large and increasing population
size the world population is still expected to
increase substantially before stabilizing.
Progress Towards Population Stabilization
South & Central America
Africa
Asia
Developed
Developing
Demographics in the USA
‣ The baby bust that followed the baby boom was largely due
to delayed marriage, contraception, and abortion.
‣ In 2006, the total fertility rate in the United States was slightly
> 2.0
Demographics in the USA
‣ 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. Population
increase in recent years has been because of
immigration
‣ Current US
Population:
309,786,186
47 years
Life expectancy
77 years
8%
Married women working
outside the home
81%
15%
High school
graduates
83%
10%
Homes with
flush toilets
Homes with
electricity
Living in
suburbs
Hourly manufacturing
job wage (adjusted for
inflation)
Homicides per
100,000 people
98%
2%
99%
10%
52%
1900
$3
2000
$15
1.2
5.8
Developed Countries
‣ High rates of resource use because of the availability of resources,
production, and waste.
‣ Result in high levels of pollution and environmental degradation per
person because of control methods, clean up, and education.
‣ The measure of a country’s economic growth is the Gross National
Product (GNP) or the Gross Domestic Product (GDP).
‣ The Human Development Index is also commonly used to determine
development.
Most developed countries have a
GDP that is high and a population
growth rate that is low.
Developing Countries
‣ China, the largest, has taken drastic population control methods.
‣ By 2050, India is predicted to pass China. Pakistan is projected to
become 3rd (the US is 3rd now.)
‣ Russia is losing 600,000 people a year, after being the 4th largest
country in 1950.
‣ Environmentalists are concerned about resource use because
developing countries are increasing their standard of living.
India’s Population Control
• India has tried population
control methods with modest
success. Poor planning,
bureaucratic inefficiency, low
status of women and lack of
support have led to low
success. The family planning
method calls for:
Education of women including
basic literacy.
Encouraged education of
contraception use among
women & birth spacing.
• Possible problems include:
Cultural/Social issues.
Cost of programs.
China’s Population Control
• China has used a government-
enforced program, “One-Child
Policy”, to reduce the fertility rate.
The One-Child Policy includes:
Paid leave to women for fertility
operations.
Monthly Subsidy to one-child families.
Job priorities for only children.
Housing preferences.
Additional food rations.
Monetary compensation.
‣ Problems include:
Preference toward gender
Increase in orphans
Consequences or punishment for
Percentage of world
population
20%
1.1 billion
1.3 billion
1.4 billion
1.6 billion
Population
Population (2050)
(estimated)
Illiteracy (% of adults)
Total fertility rate
Infant mortality rate
47%
17%
36%
Population under age 15 (%)
Population growth rate (%)
20%
1.6%
0.6%
2.9 children per women (down from 5.3 in 1970)
1.6 children per women (down from 5.7 in 1972)
58
27
62 years
70 years
Life expectancy
Percentage living
below $2 per day
GDP PPP per capita
India
China
17%
80
47
$3,120
$5,890
1994 Global (Cairo) Conference:
Population & Development
‣ The summit at Cairo, Egypt, encouraged
action to stabilized the world’s population at
7.8 billion by 2050, instead of the projected
11-12.5 billion.
Provide universal access to family-planning
services
Improve the health care of infants, children &
pregnant women and improve the status of
women by expanding education & job
opportunities
Encourage development of national population
policies
Increase men’s involvement in child-rearing
responsibility & family planning and increase
access to education for girls
Take steps to eradicate poverty
Environmental Impact
‣ Deforestation destroys habitats and reduces
biodiversity:
Farming and the creation of monocultures,
housing or development projects that cause
urbanization, fuel from wood, and fossil fuel
recovery from mining.
‣ Fossil fuel burning releases CO2:
Results in climate change, change in temperature
and precipitation patterns changing habitats.
‣ Intensive fishing and fish farming:
Spreads disease to native fish and causes
unsustainable fish populations.
‣ Diversion and damming of water:
For agricultural, municipal, and industrial use
reduces water supplies.
‣ Building landfills:
To accommodate increased amounts of trash.