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LECTURE PRESENTATIONS
For CAMPBELL BIOLOGY, NINTH EDITION
Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson
Chapter 36
Population Ecology
Lectures by
Erin Barley
Kathleen Fitzpatrick
© 2011 Pearson Education, Inc.
• Population ecology is the study of populations in
relation to their environment, including
environmental influences on density and
distribution, age structure, and population size
• A population is a group of individuals of a single
species living in the same general area
• Populations are described by their boundaries and
size
© 2011 Pearson Education, Inc.
Density and Dispersion
• Density is the number of individuals per unit area
or volume
• Dispersion is the pattern of spacing among
individuals within the boundaries of the population
© 2011 Pearson Education, Inc.
Density: A Dynamic Perspective
In most cases, it is impractical or impossible to count
all individuals in a population
• Immigration is the influx of new individuals from
other areas
• Emigration is the movement of individuals out of
a population
• Sampling techniques - Population size can be
estimated by either extrapolation from small
samples, an index of population size (e.g., number
of nests), or the mark-recapture method
© 2011 Pearson Education, Inc.
Figure 53.3
Births
Births and immigration
add individuals to
a population.
Immigration
Deaths
Deaths and emigration
remove individuals
from a population.
Emigration
Figure 53.4
(a) Clumped
Patterns of Dispersion
(b) Uniform
(c) Random
• Most organisms exhibit a clumped dispersion
pattern (i.e. herds, packs, etc).
© 2011 Pearson Education, Inc.
Figure 53.4a
(a) Clumped
• A uniform dispersion is one in which individuals
are evenly distributed
• It may be influenced by social interactions such as
territoriality, the defense of a bounded space
against other individuals
• Plants – secrete toxins into soil to prevent growth
of neighboring plants within a certain distance. (ie.
Sage plant)
© 2011 Pearson Education, Inc.
Figure 53.4b
(b) Uniform
• In a random dispersion, the position of each
individual is independent of other individuals
• It occurs in the absence of strong attractions or
repulsions
© 2011 Pearson Education, Inc.
Figure 53.4c
(c) Random
Demographics
• Demography is the study of the vital statistics of a
population and how they change over time
• Death rates and birth rates are of particular
interest to demographers
© 2011 Pearson Education, Inc.
Table 53.1
Survivorship Curves
• A survivorship curve is a graphic way of
representing the data in a life table
• The survivorship curve for Belding’s ground
squirrels shows a relatively constant death rate
© 2011 Pearson Education, Inc.
Figure 53.5
Number of survivors (log scale)
1,000
100
Females
10
Males
1
0
2
4
6
Age (years)
8
10
• 3 Types of Survivorship Curves:
– Type I: low death rates during early and middle life and
an increase in death rates among older age groups
– Type II: a constant death rate over the organism’s life
span
– Type III: high death rates for the young and a lower
death rate for survivors
• Many species are intermediate to these curves
© 2011 Pearson Education, Inc.
Number of survivors (log scale)
Figure 53.6
1,000
I
100
II
10
III
1
0
50
Percentage of maximum life span
100
Measuring Population Growth Rates
Change in
Immigrants
Emigrants
population  Births  entering  Deaths  leaving
size
population
population
• For measuring GLOBAL changes - immigration
and emigration are ignored, a population’s growth
rate equals birth rate minus death rate ONLY!
© 2011 Pearson Education, Inc.
Exponential Growth Model
• Exponential population growth is population
increase under idealized condition
• Idealized situations help us understand the
capacity of species to increase and the conditions
that may facilitate this growth
Exponential population growth results in a J-shaped
curve
© 2011 Pearson Education, Inc.
Figure 53.7
2,000
Population size (N)
dN
= 1.0N
dt
1,500
dN
= 0.5N
dt
1,000
500
0
5
10
Number of generations
15
Figure 53.8
Elephant population
8,000
6,000
4,000
2,000
0
1900 1910
1920
1930 1940
Year
1950
1960
1970
The elephant population in Kruger National Park, South
Africa, grew exponentially after hunting was banned
The logistic model describes how a population grows
more slowly as it nears its carrying capacity
• Exponential growth cannot be sustained for long in
any population
• A more realistic population model limits growth by
incorporating carrying capacity
• Carrying capacity (K) is the maximum population
size the environment can support
• Carrying capacity varies with the abundance of
limiting resources
© 2011 Pearson Education, Inc.
The Logistic Growth Model
• In the logistic population growth model, the per
capita rate of increase declines as carrying
capacity is reached
• The logistic model of population growth produces
a sigmoid (S-shaped) curve
© 2011 Pearson Education, Inc.
Figure 53.9
Exponential
growth
dN
= 1.0N
dt
Population size (N)
2,000
1,500
K = 1,500
Logistic growth
1,500 – N
dN
= 1.0N
1,500
dt
(
1,000
Population growth
begins slowing here.
500
0
0
5
10
Number of generations
15
)
Number of Daphnia/50 mL
Number of Paramecium/mL
Figure 53.10
1,000
800
600
400
200
0
0
5
10
Time (days)
15
(a) A Paramecium population in
the lab
180
150
120
90
60
30
0
0
20
40
60 80 100 120 140 160
Time (days)
(b) A Daphnia population in the lab
Many factors that regulate population
growth are density dependent
• There are two general questions about regulation
of population growth
– What environmental factors stop a population
from growing indefinitely?
– Why do some populations show radical
fluctuations in size over time, while others remain
stable?
© 2011 Pearson Education, Inc.
Mechanisms of Density-Dependent
Population Regulation
• Density-dependent birth and death rates are an
example of negative feedback that regulates
population growth
• Density-dependent birth and death rates are
affected by many factors, such as competition for
resources, territoriality, disease, predation, toxic
wastes, and intrinsic factors
© 2011 Pearson Education, Inc.
Density-Dependent Controls
• Competition for resources
• Predation
• Parasitism
• Disease
Competition for Resources
• In crowded populations, increasing population
density intensifies competition for resources and
results in a lower birth rate
© 2011 Pearson Education, Inc.
Toxic Wastes
• Accumulation of toxic wastes can contribute to
density-dependent regulation of population size
© 2011 Pearson Education, Inc.
Predation
• As a prey population builds up, predators may
feed preferentially on that species
© 2011 Pearson Education, Inc.
Intrinsic Factors
• For some populations, intrinsic (physiological)
factors appear to regulate population size
© 2011 Pearson Education, Inc.
Territoriality
• In many vertebrates and some invertebrates,
competition for territory may limit density
© 2011 Pearson Education, Inc.
Disease
• Population density can influence the health and
survival of organisms
• In dense populations, pathogens can spread more
rapidly
© 2011 Pearson Education, Inc.
Figure 53.17f
Density-Independent Controls
• Natural disasters
• Severe weather
• Pollution
• Pesticide spraying
Population Cycles: Scientific Inquiry
• Some populations undergo regular boom-and-bust
cycles
• Lynx populations follow the 10-year boom-andbust cycle of hare populations
© 2011 Pearson Education, Inc.
Figure 53.19
Snowshoe hare
120
9
Lynx
80
6
40
3
0
0
1850
1875
1900
Year
1925
Number of lynx
(thousands)
Number of hares
(thousands)
160
Figure 53.18
2,500
Wolves
Moose
40
2,000
30
1,500
20
1,000
10
500
0
1955
0
1965
1975
1985
Year
1995
2005
Number of moose
Number of wolves
50
Figure 53.22
The Global Human Population
• The human population increased
relatively slowly until about 1650 and
then began to grow exponentially
6
5
4
3
2
The Plague
1
0
8000
BCE
4000
BCE
3000
BCE
2000
BCE
1000
BCE
0
1000
CE
2000
CE
Human population (billions)
7
• The global population is more than 6.8 billion
people
• Though the global population is still growing, the
rate of growth began to slow during the 1960s
© 2011 Pearson Education, Inc.
Figure 53.23
2.2
2.0
Annual percent increase
1.8
1.6
1.4
2009
1.2
Projected
data
1.0
0.8
0.6
0.4
0.2
0
1950
1975
2000
Year
2025
2050
Regional Patterns of Population Change
• To maintain population stability, a regional human
population can exist in one of two configurations
– Zero population growth =
High birth rate – High death rate
– Zero population growth =
Low birth rate – Low death rate
• The demographic transition is the move from the
first state to the second state
© 2011 Pearson Education, Inc.
Figure 53.24
Rapid growth
Afghanistan
Male
10 8
Female
6 4 2 0 2 4 6
Percent of population
Slow growth
United States
Age
85+
80–84
75–79
70–74
65–69
60–64
55–59
50–54
45–49
40–44
35–39
30–34
25–29
20–24
15–19
10–14
5–9
0–4
8 10
8
Male
Female
6 4 2 0 2 4 6
Percent of population
No growth
Italy
Age
85+
80–84
75–79
70–74
65–69
60–64
55–59
50–54
45–49
40–44
35–39
30–34
25–29
20–24
15–19
10–14
5–9
0–4
8
8
Male
Female
6 4 2 0 2 4 6 8
Percent of population
• The demographic transition is associated with an
increase in the quality of health care and improved
access to education, especially for women
• Most of the current global population growth is
concentrated in developing countries
• Age structure diagrams can predict a population’s
growth trends
• They can illuminate social conditions and help us
plan for the future
© 2011 Pearson Education, Inc.
Infant Mortality and Life Expectancy
• Infant mortality and life expectancy at birth vary
greatly among developed and developing
countries but do not capture the wide range of the
human condition
© 2011 Pearson Education, Inc.
80
60
50
Life expectancy (years)
Infant mortality (deaths per 1,000 births)
Figure 53.25
40
30
20
60
40
20
10
0
0
Indus- Less industrialized
trialized
countries countries
Indus- Less industrialized
trialized
countries countries
Global Carrying Capacity
How many humans can the biosphere support?
• Population ecologists predict a global population
of 7.810.8 billion people in 2050
• The carrying capacity of Earth for humans is
uncertain
• The average estimate is 10–15 billion
© 2011 Pearson Education, Inc.
Limits on Human Population Size
• The ecological footprint concept summarizes the
aggregate land and water area needed to sustain
the people of a nation
• It is one measure of how close we are to the
carrying capacity of Earth
• Countries vary greatly in footprint size and
available ecological capacity
© 2011 Pearson Education, Inc.
Figure 53.26
Gigajoules
> 300
150–300
50–150
10–50
< 10
Figure 53.26 Annual per capita energy use
around the world.
LECTURE PRESENTATIONS
For CAMPBELL BIOLOGY, NINTH EDITION
Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson
Chapter 35 Review Q’s
Population Ecology
Questions prepared by
Eric Ribbens
Western Illinois University
by
JohnLectures
Zarnetske
Hoosick Falls Erin
CentralBarley
Schools
Kathleen Fitzpatrick
© 2011 Pearson Education, Inc.
Which of the following sets of measurements is the
most useful when studying populations?
a) gene frequency over time and the ratio of reproductive to
nonreproductive individuals
b) density, dispersion, and demographics of a population
c) minimum and minimum amounts of precipitation and
annual temperature extremes
d) ratio of predators and the number of immigrants and
emigrants
e) annual precipitation averages and mean annual
temperatures
Population ecologists are primarily
interested in
a) understanding how biotic and abiotic factors influence the
density, distribution, size, and age structure of
populations.
b) the overall vitality of a population of organisms.
c) how humans affect the size of wild populations of
organisms.
d) studying interactions among populations of organisms
that inhabit the same area.
e) how populations evolve as natural selection acts on
heritable variations among individuals and changes in
gene frequency.
A mark-recapture study would be a
good way to find out how many
a) queens live in a beehive.
b) cubs that black bears in Minnesota are likely
to have.
c) pine trees live in a forest.
d) fish live in a lake.
e) people speed on an interstate.
Imagine that a species of fish used to be a broadcast spawner
(producing many eggs that then get no subsequent parental care) but
has evolved to be a mouth brooder (holding the eggs in the parent’s
mouth until they hatch and then caring for the young for a while). We
would expect the survivorship curve of this species to shift
a)
b)
c)
d)
e)
from Type I to Type II or III.
from Type II to Type I.
from Type III to Type I or II.
from Type II to Type III.
The survivorship type
would vary unpredictably.
© 2011 Pearson Education, Inc.
The exponential growth model describes the increase in population size
of a population that is not constrained by resources or space. The graph
shows the elephant population in Kruger National Park, which appears
to have been reproducing exponentially from 1900 to 1963. From this
graph, you can tell that
a) none of the elephants died.
b) a female elephant living around
1960 was more likely to have a
baby than a female elephant
living around 1920.
c) the elephants adapted to the
new park conditions around
1955.
d) the vegetation the elephants eat
could support more than 5,000
elephants.
e) the more elephants there are,
the more tourists will visit the
park.
The logistic model incorporates the idea of K, the carrying capacity,
which is the maximum number of individuals the ecosystem can sustain
over time. Essential to this idea is the concept that population growth
rates are reduced when the population size approaches K. Look at the
graphs on the next slide. Both Paramecium and Daphnia have
population dynamics that stabilize around K. However, Daphnia
overshot their carrying capacity, but Paramecium did not. This is
probably because
a) Paramecium are a single-celled organism.
b) Daphnia live in water.
c) the Daphnia had to learn what their carrying capacity was.
d) the Paramecium population had a bigger K (about 800) than
Daphnia (about 120).
e) something about Daphnia responds differently to K than
Paramecium.
From the following graph you can tell that
a) families in Mexico are still
more likely to be bigger than
families in Sweden.
b) more people live in Mexico
than in Sweden.
c) birth rates and death rates do
not appear to be correlated.
d) a Swedish person born in
1900 is more likely to be dead
than a Mexican person born
in 1900.
e) these populations are
probably far away from their
carrying capacity.
The graph shows the percent increase in the global human
population. There is a sharp dip around 1960, which the
legend says is due mainly to a famine in China in which 60
million people died. The graph also predicts that the percent
increase is dropping and will continue to drop throughout
the 21st century. Which of the following statements is true?
a) The famine in China and the 21st-century decline are both examples of
density-independent factors.
b) The famine in China and the 21st-century decline are both examples of
density-dependent factors.
c) The famine in China was density-independent, but the 21st-century
decline is density dependent.
d) The famine in China was density-dependent, but the 21st-century decline
is density independent.
e) Because the causes of the famine and the 21st-century decline are
different, you cannot tell whether they are density dependent.
Most ecologists agree that people should not be
using more than 1.7 ha of resources if they
want to be sustainable. People in the United
States use an average of 10 ha. This implies
that
a) the ecological footprint concept is flawed.
b) the United States has more land than other countries
do.
c) U.S. rates of resource consumption are too high.
d) U.S. people are happier.
e) U.S. people are less likely to emigrate.