1. Chapter 36
Population Dynamics

2. The Spread of Shakespeare’s Starlings
The Spread of Shakespeare’s Starlings
The European Starling
Has become an abundant and destructive pest in North America
European starling

3. Starling populations have become very successful
Starling populations have become very successful
And spread throughout North America since their introduction in 1890
Current
1955
1945
1935
1925
1915
1905
The spread of starlings across North America

4. Population ecology
Is concerned with changes in population size and the factors that regulate populations over time

5. 36.1 Population ecology is the study of how and why populations change
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

6. 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

7. Environmental and social factors
Environmental and social factors
Influence the spacing of individuals in various dispersion patterns: clumped, uniform, or random
Figure 36.2A
Figure 36.2B

8. 36.3 Life tables track mortality and survivorship in populations
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

9. The three types of survivorship curves
The three types of survivorship curves
Reflect species’ differences in reproduction and mortality
Percentage of survivors (log scale)
100 10 1
0.1 50
III II I
Percentage of maximum life span
Figure 36.3

10. 36.4 Idealized models help us understand population growth

11. The Exponential Growth Model
The Exponential Growth Model
Exponential growth
Is the accelerating increase that occurs when growth is unlimited

12. The equation G  rN describes this J-shaped curve
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
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
Number of bacterial cells (N) 70 50 30 10
140
G = r N
Time (min)
Figure 36.4A

13. Breeding male fur seals
Limiting Factors and the Logistic Growth Model
Limiting factors
Are environmental factors that restrict population growth
Breeding male fur seals
(thousands) 10 8 6 4 2
1915
1925
1935
1945
Year
Figure 36.4B

14. 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
Number of individuals (N) K
Time
G = r N
(K – N)
Figure 36.4C

15. 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

16. 36.5 Multiple factors may limit population growth
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
2.8 10 20 30 40 50 60 70 80
Density of females
Clutch size
Figure 36.5A

17. Abiotic factors such as weather May limit many natural populations
Abiotic factors such as weather
May limit many natural populations
Exponential
growth
Sudden
decline
Number of aphids
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Figure 36.5B

18. Most populations
Are probably regulated by a mixture of factors, and fluctuations in numbers are common
Time (years)
1975
1980
1985
1990
1995
2000 20 40 80 60
Number of females
Figure 36.5C

19. 36.6 Some populations have “boom-and-bust” cycles
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
1850
1875
1900
1925 9 6 3
Snowshoe hare
Lynx
Hare population size
(thousands)
Lynx population size
Year
Figure 36.6

20. LIFE HISTORIES AND THEIR EVOLUTION
36.7 Evolution shapes life histories
An organism’s life history
Is the series of events from birth through reproduction to death

21. Populations with so-called r-selection life history traits
Populations with so-called r-selection life history traits
Produce many offspring and grow rapidly in unpredictable environments
Figure 36.7A

22. Populations with K-selected traits
Raise few offspring and maintain relatively stable populations

23. Are shaped by natural selection
Life history traits
Are shaped by natural selection
Experimental
transplant of
guppies
Predator: Killifish;
preys mainly on small,
immature guppies
Guppies: Larger at
sexual maturity than
those in pike-cichlid
pools
Predator: Pike-cichlid;
preys mainly on large,
mature guppies
Guppies: Smaller at
those in killifish pools
Figure 36.7B

24. Yield (thousands of metric tons)
CONNECTION
36.8 Principles of population ecology have practical applications
Principles of population ecology
Are useful in managing natural resources
900
800
700
600
500
400
300
200
100
1960
1970
1980
1990
2000
Yield (thousands of metric tons)
Figure 36.8

25. THE HUMAN POPULATION CONNECTION
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
The Plague 6 5 4 3 2 1
8000
B.C.
4000
3000
2000
1000
A.D.
Human population size (billions)
Figure 36.9A

26. The ecological footprint
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
Available ecological capacity (ha per person)
Ecological footprint (ha per person)
Japan UK
Spain
Germany
Netherlands
Norway
USA
World
China
India
Sweden
Canada
Australia
New Zealand
Figure 36.9B

27. The ecological capacity of the world
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 Zaire
Figure 36.9C

28. Birth or death rate per 1,000 population
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
1900
1925
1950
1975
2000
2025
2050
Year
Birth rate
Death rate
Birth or death rate per 1,000 population
Figure 36.10A

29. The age structure of a population
The age structure of a population
Is the proportion of individuals in different age-groups
Affects its future growth
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 4 6 2
Percent of population
Primary
reproductive
ages
Rapid growth
Slow growth
Decrease
Afghanistan
United States
Italy
Male
Female
Figure 36.10B

30. Increasing the status of women
May help to reduce family size