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Population Dynamics (4.1)
State Standard
SB4C. Relate environmental conditions to
successional changes in ecosystems.
C
A
B
Chapter 4
Population Ecology
4.1 Population Dynamics
Population Characteristics (AKA Demographics)
Population Density
 The number of organisms per unit area
Spatial Distribution
 Dispersion is the pattern of spacing of a
population.
Demography – the study of human population
size, density, distribution, movement, and
birth/death rates.
Chapter 4
Population Ecology
4.1 Population Dynamics
Population Characteristics
Population Density
 The number of organisms per unit area
Spatial Distribution
 Dispersion is the pattern of spacing of a
population.
 Uniform – equally dispersed – territorial animals
Chapter 4
Population Ecology
4.1 Population Dynamics
Population Characteristics
Population Density
 The number of organisms per unit area
Spatial Distribution
 Dispersion is the pattern of spacing of a
population.
 Uniform – equally dispersed – territorial animals
 Clumped – groups – herding animals
Chapter 4
Population Ecology
4.1 Population Dynamics
Population Characteristics
Population Density
 The number of organisms per unit area
Spatial Distribution
 Dispersion is the pattern of spacing of a
population.
 Uniform – equally dispersed – territorial animals
 Clumped – groups – herding animals
 Random – no pattern – usually based on resources
Chapter 4
Population Ecology
4.1 Population Dynamics
Population Characteristics Cont’d
Population Range
 A species might not be
able to expand its
population range because
it cannot survive the
abiotic conditions found in
the expanded region.
Common dolphin
Pupfish
Demography – the study of human population
size, density, distribution, movement, and
birth/death rates.
Chapter 4
Population Ecology
4.1 Population Dynamics
Population-Limiting Factors
 There are two categories of limiting factors—
density-independent factors and densitydependent factors.
Chapter 4
Population Ecology
4.1 Population Dynamics
Population Limiting Factors Cont’d
Density-Independent Factors (generally abiotic)
 Any factor in the environment that does
not depend on the number of members
in a population per unit area is a
density-independent factor.
 Weather events
 Fire
 Human alterations of the landscape
 Air, land, and water pollution
Chapter 4
Population Ecology
4.1 Population Dynamics
Population Limiting Factors Cont’d
Density-Dependent Factors
 Any factor in the environment that depends
on the number of members in a population
per unit area is a density-dependent factor.
 Biotic factors
 Disease
 Competition
 Parasites
Population
Biology
Chapter 4
Population Ecology
Population Growth Rate
 The population growth rate (PGR)
explains how fast a given population grows.
 Growth Rate is affected by…
 Limiting Factors
Chapter 4
Population Ecology
Population Growth Rate
 The population growth rate (PGR)
explains how fast a given population grows.
 Growth Rate is affected by…
 Limiting Factors
 Natality (# of births)
Chapter 4
Population Ecology
Population Growth Rate
 The population growth rate (PGR)
explains how fast a given population grows.
 Growth Rate is affected by…
 Limiting Factors
 Natality (# of births)
 Mortality (# of deaths)
Chapter 4
Population Ecology
Population Growth Rate
 The population growth rate (PGR)
explains how fast a given population grows.
 Growth Rate is affected by…
 Limiting Factors
 Natality (# of births)
 Mortality (# of deaths)
 Immigration (# of individuals entering)
Chapter 4
Population Ecology
Population Growth Rate
 The population growth rate (PGR)
explains how fast a given population grows.
 Growth Rate is affected by…
 Limiting Factors
 Natality (# of births)
 Mortality (# of deaths)
 Immigration (# of individuals entering)
 Emigration (# of individuals exiting)
Chapter 4
Population Ecology
4.1 Population Dynamics
Population Growth Rate Cont’d
Exponential Growth Model
 Exponential growth
occurs when the
growth rate is
proportional to the
size of the population.
Graph shows a
J-shaped Curve!
 All populations grow
exponentially until
some limiting factor slows the population’s
growth.
Chapter 4
Population Ecology
Population Growth Rate Cont’d
Logistic Growth Model
 The population’s growth
slows or stops following
exponential growth, at
the environment’s
carrying capacity.
 Carrying capacity is the
largest # of individuals
an environment can
support.
Graph shows an
S-shaped Curve!
Chapter 4
Population Ecology
4.1 Population Dynamics
Population Growth Rate Cont’d
 A population stops increasing when
natality is less than mortality or when
emigration exceeds immigration.
 Carrying capacity is limited by the
energy, water, oxygen, nutrients, & space,
as well as other limiting factors.
Chapter 4
Population Ecology
Chapter 4
Population Ecology
4.1 Population Dynamics
Reproductive Patterns
 Species of organisms vary in the number of
births per reproduction cycle, in the age that
reproduction begins, and in the life span of
the organism.
Chapter 4
Population Ecology
4.1 Population Dynamics
Reproductive Patterns Cont’d
 The rate strategy, or r-strategy, is an
adaptation for living in an environment where
fluctuation in biotic or abiotic factors occur.
 An r-strategist is generally a small organism.
 Short life span
 Produces many offspring
Chapter 4
Population Ecology
4.1 Population Dynamics
Reproductive Patterns Cont’d
 The carrying-capacity strategy, or k-strategy,
is an adaptation for living in stable
environments.
 A k-strategist is generally a larger organism.
 Long life span
 Produces few offspring
Chapter 4
Population Ecology
Chapter Diagnostic
Questions
What term is used to describe the number of
individuals moving into a population?
A. emigration
B. imitation
C. immigration
D. migration
0%
A
0%
B
1.
A
0%2.
0%B
3.
4.
C
D
C
D
Chapter 4
Population Ecology
Chapter Diagnostic
Questions
What is population density?
A. pattern of spacing of a
population in an area
B. number of organisms
in an area
C. characteristics of
a population
D. manner in which a
population grows
0%
A
0%
B
1.
A
0%2.
0%B
3.
4.
C
D
C
D
Chapter 4
Population Ecology
4.1 Formative
Questions
Which is a density-dependent factor?
A. disease
B. fire
C. flooding
D. weather
0%
A
0%
B
1.
A
0%2.
0%B
3.
4.
C
D
C
D
Chapter 4
Population Ecology
4.1 Formative
Questions
Which is a density-independent factor?
A. competition
B. extreme cold
C. parasites
D. predation
0%
A
0%
B
1.
A
0%2.
0%B
3.
4.
C
D
C
D
Chapter 4
Population Ecology
4.1 Formative
Questions
Which factor can limit the carrying capacity
of a population?
A. emigration
B. predation
C. available nutrients
D. extreme temperatures
0%
A
0%
B
1.
A
0%2.
0%B
3.
4.
C
D
C
D
Chapter 4
Population Ecology
Chapter Assessment
Questions
Which type of population
growth model does this
graph represent?
A. exponential
B. spatial
C. genetic
D. logistic
A
B
C
0%
D
D
0%
C
0%
B
A
0%
1.
2.
3.
4.
Chapter 4
Population Ecology
Chapter Assessment
Questions
Use the graph to explain the growth of the
mice population.
Chapter 4
Population Ecology
Standardized Test
Practice
The ecologist finds that over a 1000m2 plot of
tundra, lemmings tend to concentrate in clumps
in drier areas. What is the term for this pattern
of spacing?
A. density
B. dispersion
C. logistic spacing
D. spatial distribution
A
B
C
D
0%
D
0%
C
0%
B
A
0%
1.
2.
3.
4.
Chapter 4
Population Ecology
Standardized Test
Practice
Brine shrimp are able to survive only in certain
lakes that have a very high salt concentration.
Which is the correct population characteristic of
brine shrimp?
A
B
0%C
D
D
0%
1.
2.
0%
3.
4.
C
A
0%
B
A. It is density-dependent.
B. It is limited by biotic factors.
C. It has a limited spatial
distribution.
D. It is randomly dispersed
in the environment.
Chapter 4
Population Ecology
Standardized Test
Practice
0%
1.
2.
3. 0%
4.
A
B
C
0%
D
D
A
0%
B
A. Biotic factors have made
survival difficult.
B. The population has reached
its carrying capacity.
C. Density-independent factors
have slowed the growth of
the population.
D. Immigration into the
population has reached the
maximum limit.
C
Why does the population
growth level off at 10,000?
Chapter 4
Population Ecology
Standardized Test
Practice
Which organism is the best example of
a k-strategist?
1.
2.
3.
4.
0%
C
0%
B
A
0%
A
B
C
D
0%
D
A. wolf
B. grasshopper
C. rabbit
D. whale