Transcript size of a population

Population Dynamics
Population Characteristics

Population Density
number of
organisms per unit
area

Population Dispersion the pattern of spacing
of a population within an area
3 Types of Population Dispersion
Interactive: Visualizing Population Dispersion
Population Growth
Population Growth Rate (PGR) explains how
fast a given population grows


=
(
(
Change in
population
size
Births
+
Immigration
-(
(

Deaths
+
Emigration
Immigration = movement INTO a population
Emigration = movement OUT OF a
population (think EXIT)
Population Growth

Population Growth Rate (PGR) Equation
Solve This: In the year 2000, the population of
Douglasville was 20,065. In the year 2010, the
population of Douglasville was 30,961. How much did
the population grow during this 10 year period?
Use the Population Growth Rate Equation to figure this
out!
Answer:
30,961 – 20,065 X 100 = 54%
20,065
Exponential (Unrestricted) Growth
 The
growth of the population accelerates
at a rapid pace
 There is no limit on the population size …
yet
 Shape is described
as a J-Curve
What stops or slows
population growth?
Limiting Factors
 Any
abiotic or biotic factor that
restricts the numbers, reproduction,
or distribution of organisms
 Examples:
– sunlight, climate, temperature (abiotic
factors)
– food supply (prey), predation,
competition (biotic factors)
Limiting Factors
2 types of limiting factors
 Density-dependent limiting factors
 Density-independent limiting factors
Density-Dependent Factors
 Any
factor that depends on the size
of a population
 Examples:
- Predation
- Disease (High population = easy
transmission)
- Parasites
- Competition (As competition increases,
resources such as food or space
decrease, or become limited)
Competiton: Wolf vs. Moose
One’s growth depends on the other’s population
Density-Independent Factors
 Any
factor that DOES NOT depend on
the size of a population
 Examples:
– Flooding
– Drought
– Tornadoes
– Fire
– Pollution
– Human alterations to the landscape
Carrying Capacity
 The
maximum number of individuals
in a species that an environment can
support for the long term
Carrying Capacity
 Rate
of population growth slows
down because of the influence of
limiting factors.
 Logistic
 Shape
Growth
is described
as an S-Curve
Carrying Capacity Graphs
What is the carrying capacity?
Carrying Capacity
What is the carrying capacity?
Carrying Capacity
What is the carrying capacity?
Carrying Capacity
What is the carrying capacity?
of snowshoe hare
 of lynx
