Transcript Density independent

Populations
Slide # 2
Important Vocabulary
1. Birth rate: number of births in a population in one year
2. Death rate: number of deaths in a population in one year
3. Immigration: number of individuals that move into a
population
4. Emigration: number of individuals that move out of a
population
Slide # 3
Populations and Their Growth
1.Growth Rate: the change in
a population’s size
– “A” = Lag phase; slow
growth
– “B” exponential growth
– “C” transitional phase
– “D” carrying capacity
Carrying capacity is NOT fixed for any population. It can
change from one season to another.
What affects carrying capacity?
Disease, food availability, water availability, predators
Slide # 4
Positive Population Growth
1. Occurs when birth rate is higher than the death rate
2. Usually occurs when conditions are ideal; will increase
until something stops it
Human Population
Growth Curve
Technology has greatly
influenced the carrying
capacity of human populations
Slide # 5
Negative Population Growth
1. Occurs when birth rate is lower than death rate
a. Ex. Overgrazing and drought left this area with out
enough resources to sustain all of the wildlife.
b. individuals die and the population decreases.
Slide # 7
Population Cycles: Boom & Bust
The human population
experienced a boom
(baby boom) after world
war II.
Boom
Bust
Boom: Birth rate is higher than death rate
Bust: Birth rate is lower than death rate
Slide # 8
Limiting Factors: Limit Population Growth
Limiting factors: help stabilize population numbers when the
population reaches carrying capacity for that ecosystem
a. Density independent: factors that affect all members of
the population equally if population is dense or not.
 Natural disasters: floods, wildfires, tornadoes, pollution,
habitat destruction
b. Density dependent: factors that affect crowded
populations
 EX: competition, predation, crowding and stress,
parasitism, and disease
 Competition for limited resources is the most important
limiting factor that affects carrying capacity.
What type of limiting factor is shown in each picture?