Population Growth
Population
• all of the individuals of a species that
live together in one place at one time
Population Characteristics
• features that describe interactions
between the population and its
environment
1.
2.
3.
4.
Geographic Distribution
Population Density
Age Structure
Growth Rate
1. Geographic Distribution
• a population’s range or area that it
inhabits
2. Population Density
• the number
of individuals
per unit area
3. Age Structure
• the age distribution
of a population
– how young or old the
population is
– generally looks like a
pyramid as a
population is growing
4. Growth Rate
• the speed of a population’s growth (or decline)
• affected by four factors
1. Mortality
•
death rate
2. Natality
•
birth rate
4. Growth Rate
• the speed of a population’s growth (or decline)
• affected by four factors
3. Immigration
•
rate of new individuals entering the population who
were born outside of the population
4. Emigration
•
rate of individuals leaving the population for another
area
Linear vs. Exponential Growth
Exponential Growth
• occurs when
individuals continue
to reproduce at a
constant rate
Exponential Growth
• occurs under “ideal”
conditions
– unlimited food,
water, shelter, etc.
– protection from
predators and
disease
Logistic Growth
• occurs when a
population’s growth
slows or stops
following
exponential growth
– occurs because
resources become
less available
Carrying Capacity
• the largest number of individuals an
environment can support over an extended
period of time
So what can cause a
population’s growth rate to
slow down or even decline?
Limiting Factors
• any factor that causes population
growth to decrease
Limiting Factors
Density Dependent
• a limiting factor that depends on population
size
– predation
– competition
– parasitism
– disease
Density Independent
• affect all populations similarly regardless of
the population size
– weather
– natural disasters
– human activities
Human Population Growth
• Historical Overview
– The size of the human population has increased
over time. It has increased very quickly the last
couple hundred years…Why???
• Agriculture and Industry
• Reliable Food Supply
• Improved Sanitation
• Medical and Health Care
Human Population Growth
Demography
• scientific study of
human populations
Human Population Growth
Demographic Transition
• a dramatic change in
birth and death rates
Human Population Growth
Age Structure Diagram
• model for predicting future population
growth or decline
Age Structure Diagram
Age Structure Diagram
Age Structure Diagram
Age Structure Diagram