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Transcript of Chapter 36
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
PowerPoint Lectures forBiology: Concepts and Connections, Fifth Edition – Campbell, Reece, Taylor, and Simon
Lectures by Chris Romero
Chapter 36Chapter 36
Population Dynamics
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
The Spread of Shakespeare’s Starlings
• The European Starling
– Has become an abundant and destructive pest in North America
Europeanstarling
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• Starling populations have become very successful
– And spread throughout North America since their introduction in 1890
Current
1955
1945
1935 1925
19151905
19251935
1945
1955Current
The spread of starlings across North America
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• Population ecology
– Is concerned with changes in population size and the factors that regulate populations over time
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
36.1 Population ecology is the study of how and why populations change
• A population
– Is a group of individuals of a single species that occupy the same general area
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
POPULATION STRUCTURE AND DYNAMICS
36. 2 Density and dispersion patterns are important population variables
• Population density
– Is the number of individuals of a species per unit of area or volume
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• Environmental and social factors
– Influence the spacing of individuals in various dispersion patterns: clumped, uniform, or random
Figure 36.2A Figure 36.2B
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
36.3 Life tables track mortality and survivorship in populations
• Life tables and survivorship curves
– Predict an individual’s statistical chance of dying or surviving during each interval of the individual’s lifetime
Table 36.3
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• The three types of survivorship curves
– Reflect species’ differences in reproduction and mortality
Pe
rce
nta
ge
of
surv
ivo
rs (
log
sca
le) 100
10
1
0.10 50 100
III
II
I
Percentage of maximum life spanFigure 36.3
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
36.4 Idealized models help us understand population growth
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
The Exponential Growth Model
• Exponential growth
– Is the accelerating increase that occurs when growth is unlimited
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• The equation G rN describes this J-shaped curve
– G the population growth rate
– r an organism’s inherent capacity to reproduce
– N the population size
Figure 36.4A
Time Number of Cells
0 minutes
20
40
60
80
100
120 (= 2 hours)
3 hours
4 hours
8 hours
12 hours
1
2
4
8
16
32
64
512
4,096
16,777,216
68,719,476,736
= 20
= 21
= 22
= 23
= 24
= 25
= 26
= 29
= 212
= 224
= 236
Num
ber
of b
acte
rial c
ells
(N
)
70
60
50
30
40
20
10
00 20 40 60 80 100 120 140
G = r N
Time (min)
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Limiting Factors and the Logistic Growth Model
• Limiting factors
– Are environmental factors that restrict population growth
Bre
edin
g m
ale
fur
seal
s(t
hous
ands
)10
8
6
4
2
01915 1925 1935 1945
YearFigure 36.4B
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• Logistic growth
– Is the model that represents the slowing of population growth as a result of limiting factors
– Levels off at the carrying capacity, which is the number of individuals the environment can support
Nu
mb
er
of
ind
ivid
ua
ls (
N)
K
0Time
G = r N
G = r N(K – N)
K
Figure 36.4C
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• The equation G rN(K – N)/K describes a logistic growth curve
– Where K carrying capacity and (K – N)/K accounts for the leveling off of the curve
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36.5 Multiple factors may limit population growth
• As a population’s density increases
– Factors such as limited food supply and increased disease or predation may increase the death rate, decrease the birth rate, or both
4.0
3.6
3.8
3.4
3.2
3.0
2.80 10 20 30 40 50 60 70 80
Density of females
Clu
tch
size
Figure 36.5A
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• Abiotic factors such as weather
– May limit many natural populations
Exponentialgrowth
Suddendecline
Num
ber
of
aph
ids
Apr May Jun Jul Aug Sep Oct Nov DecFigure 36.5B
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• Most populations
– Are probably regulated by a mixture of factors, and fluctuations in numbers are common
Time (years)
1975 1980 1985 1990 1995 20000
20
40
80
60
Num
ber
of f
emal
es
Figure 36.5C
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
36.6 Some populations have “boom-and-bust” cycles
• Some populations
– Undergo regular boom-and-bust cycles of growth and decline
160
120
80
40
01850 1875 1900 1925
9
6
3
0
Snowshoe hare
Lynx
Har
e po
pula
tion
size
(tho
usan
ds)
Lynx
pop
ulat
ion
size
(tho
usan
ds)
Year Figure 36.6
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
36.7 Evolution shapes life histories
• An organism’s life history
– Is the series of events from birth through reproduction to death
LIFE HISTORIES AND THEIR EVOLUTION
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• Populations with so-called r-selection life history traits
– Produce many offspring and grow rapidly in unpredictable environments
Figure 36.7A
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• Populations with K-selected traits
– Raise few offspring and maintain relatively stable populations
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• Life history traits
– Are shaped by natural selection
Experimentaltransplant ofguppies
Predator: Killifish;preys mainly on small,immature guppies
Guppies: Larger atsexual maturity thanthose in pike-cichlidpools
Predator: Pike-cichlid;preys mainly on large,mature guppies
Guppies: Smaller atsexual maturity thanthose in killifish poolsFigure 36.7B
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36.8 Principles of population ecology have practical applications
• Principles of population ecology
– Are useful in managing natural resources
CONNECTION
900
800
700
600
500
400
300
200
100
01960 1970 1980 1990 2000
Yie
ld (
thou
sand
s of
met
ric t
ons)
Figure 36.8
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
THE HUMAN POPULATION CONNECTION
The Plague
6
5
4
3
2
1
08000B.C.
4000B.C.
3000B.C.
2000B.C.
1000B.C.
0 1000A.D.
2000A.D.
Hum
an p
opul
atio
n si
ze (
billi
ons)
Figure 36.9A
36.9 Human population growth has started to slow after centuries of exponential increase
•The human population
– Has been growing almost exponentially for centuries, standing now at about 6.4 billion
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• The ecological footprint
– Represents the amount of land per person needed to support a nation’s resource needs
16
14
12
10
8
6
4
2
00 2 4 6 8 10 12 14 16
Available ecological capacity (ha per person)
Eco
log
ica
l fo
otp
rint
(ha
pe
r p
ers
on
)
Japan
UK
Spain
Germany
NetherlandsNorway
USA
World
ChinaIndia
Sweden
Canada
Australia
New Zealand
Figure 36.9B
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• The ecological capacity of the world
– May already be smaller than the population’s ecological footprint
Traffic in downtown Cairo, Egypt
Manhattan,New York City
Refugee camp in ZaireFigure 36.9C
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
36.10 Birth and death rates and age structure affect population growth
• The demographic transition
– Is the shift from high birth rates and death rates to low birth rates and death rates
50
40
30
20
10
01900 1925 1950 1975 2000 2025 2050
Year
Birth rate
Death rate
Birt
h or
dea
th r
ate
per
1,00
0 po
pula
tion
Figure 36.10A
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• The age structure of a population
– Is the proportion of individuals in different age-groups
– Affects its future growth
Age85+
80–8475–7970–7465–6960–6455–5950–5445–4940–4435–3930–3425–2920–2415–1910–145–90–4
8 46 2 0 2 4 6 8 6 4 2 0 2 4 6 6 4 2 0 2 4 6
Percent of population Percent of population Percent of population
Primaryreproductive
ages
Rapid growth Slow growth Decrease
Afghanistan United States Italy
Male Female Male Female Male Female
Figure 36.10B
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• Increasing the status of women
– May help to reduce family size