Download Population Size - Warren County Schools

Population Ecology
ECOLOGISTS STUDY ENVIRONMENTS AT
DIFFERENT LEVELS OF ORGANIZATION.
Organism  Population  Community  Ecosystem  Biome
Population Ecology
 Population:
all the organisms that both belong to the same
group or species and live in the same geographical
area
Specific species at the same place at the same
time
Example:
1,738 trout in Kentucky Lake in 1986
Population Size
The size of a population is always changing!
Four factors affect the size of a population:
Immigration (coming in)
Births
Emigration (leaving)
Deaths
Population Density
 Population Density:
 The
number of individuals that live in a
defined area
 Helps scientists determine how crowded
an area is
 Formula:
# of individuals= population density
Area (units2)
Population Growth
 Population growth is based on available resources.
WATER
FOOD
SHELTER
Population Growth
Exponential Growth (J curve)
Rapid population increase due to an
abundance of resources.
Population Growth
Logistic Growth (s
curve)
Due to a population
facing limited
resources
No more will fit!!!
Population Growth
Carrying Capacity
The maximum
number of individuals
that the environment
can support
When resources run
out the population
cannot keep growing
Population Growth
Ecological Factors limit
population growth.
Limiting Factors:
Something that keeps
the size of a population
down
Limiting Factors
 Density-dependent limiting factors:
Depend on the number of individuals in a given
area.
Examples:
Predation
Competition (competing for resources)
Parasitism & disease
Have a larger effect in densely populated areas
Limiting Factors
 Density-independent limiting factors:
Limit a population’s growth regardless of the
number of individuals
Examples:
Unusual weather
Natural disasters
Human activities