Human Population Dynamics

Human Population Dynamics
How do populations change
• Immigration – movement of people or species into a
• Emmigration – movement of people or other species
out of a population
** In general these are not significant factors in
population size& DO NOT affect global population
Fertility Rates
• Replacement level fertility (RLF)
– Number of children a couple must have to replace
– 2.1 in developed countries (DCs) 2.5 in some lessdeveloped ones (LDCs)
– Have to take infant mortality into account
• Total Fertility Rate
The number of children a woman will bear
during her lifetime.
• Total Fertility Rate is decreasing globally
however world population is still increasing.
*** TFR = most significant addition to human
Projected Birth Rates by
World Population Growth Rate
• Total fertility rate = replacement rate
• Still does not equal zero population growth
because of people living longer
Factors that affect the growth rate of
Human Populations
Anything that impacts TFR (total fertlility rate)
impacts population growth.
Availability of birth control
Demand for children in the labor force
Urbanization (rural communities have children for
Base level of education for women
Religious beliefs, customs and traditions
You do
• Identify and describe two factors that affect
• Explain the difference between TFR and RLF
Factors not related to TFR that affect
The reason the worlds population has grown in
the past 100 yrs is due more to later death
rate than higher birth rate
Why are people living longer?
• Industrial Revolution improved standard of
• Clean water
• Better sanitation (fewer diseases)
• Dependable food supply
• Better health care
2 generalization about population
• The more industrialized or developed the nation the
longer the life span
• Overall health of a population can be estimated by
looking at lifespan AND mortality rate of infants.
Life span: Afghanistan = 44yrs. Japan = 80yrs
Infant Mortality: Afghanistan=121/1000
US= 6/1000
Age Structure pyramids
Demographic Transition Model
Used to predict population trends based on birth and death rates of a population.
• Environmental Resistance- anything that
slows a population’s growth – such as harsh
living conditions, lack of clean water, lack of
medical care etc.
Zero population growth occurs when
a. High birth rates and high death rates
b. Low birth rates and low death rates.
Demographic Transition - When a population
moves from situation a- to situation b
There are 4 stages that occur before a
demographic transition happens!!
Pre Industrial StateSlow growth
High birth rate
High death rate
Harsh living conditions
2. Transitional State• RAPID population growth
• High birth rates
• Lower death rates due to food, clean water,
and improved health care
3. Industrial State:
• SLOW population growth
• Birth rate drops
• Birth rate and death rate are close but not
• *** Developing countries are in this state**
4. Post Industrial State
• Population approaches or reaches zero
population growth!!!!
• Populations can drop below zero population
growth (negative growth) (russia)
Homework questions
• Describe in your own words the stages of the
demographic transition model
• What stage has high birth and low death?
• Why do countries tend towards zero
population growth when industrialization
occurs? Identify and describe 2 reasons.
One reason so many big cats are endangered
Habitat destroyed
Prey dies
Predator has no food
Species without food go extinct