Population Growth

Population Growth
• 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
Geographic Distribution
Population Density
Age Structure
Growth Rate
1. Geographic Distribution
• a population’s range or area that it
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
Linear vs. Exponential Growth
Exponential Growth
• occurs when
individuals continue
to reproduce at a
constant rate
Exponential Growth
• occurs under “ideal”
– unlimited food,
water, shelter, etc.
– protection from
predators and
Logistic Growth
• occurs when a
population’s growth
slows or stops
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
– 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
• 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