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Population Dynamics, Carrying
Capacity, and Human Population
Brian Kaestner
Saint Mary’s Hall
Thanks to Miller and Clements
Population Dynamics and Carrying
Capacity
 Population dynamics
 Zero population growth (ZPG)
 Biotic potential (intrinsic rat of increase [r])
 Environmental resistance
 Carrying capacity
 Minimum viable population (MVP)
Population Dispersion
Clumped
(elephants)
Uniform
(creosote bush)
Random
(dandelions)
Fig. 9.2, p. 199
Factors Affecting Population Size
POPULATION SIZE
Growth factors
(biotic potential)
Abiotic
Favorable light
Favorable temperature
Favorable chemical environment
(optimal level of critical nutrients)
Biotic
High reproductive rate
Generalized niche
Adequate food supply
Suitable habitat
Ability to compete for resources
Ability to hide from or defend
against predators
Ability to resist diseases and parasites
Ability to migrate and live in other
habitats
Ability to adapt to environmental
change
Decrease factors
(environmental resistance)
Abiotic
Too much or too little light
Temperature too high or too low
Unfavorable chemical environment
(too much or too little of critical
nutrients)
Biotic
Low reproductive rate
Specialized niche
Inadequate food supply
Unsuitable or destroyed habitat
Too many competitors
Insufficient ability to hide from or defend
against predators
Inability to resist diseases and parasites
Inability to migrate and live in other
habitats
Inability to adapt to environmental
change
Fig. 9.3, p. 200
Exponential and Logistic Growth
Population size (N)
Population size (N)
K
Time (t)
Fig. 9.4, p. 201
Time (t)
2.0
1.5
1.0
.5
1800 1825 1850
Fig. 9.5, p. 201
Logistic Growth
Number of reindeer
Number of sheep (millions)
Exponential Growth
1875 1900 1925
Year
2,000
1,500
1,000
500
1910
1920
1930
1940
Year
1950
Fig. 9.6, p. 201
Population Density Effects
Density-independent controls
Density-dependent controls
Natural Population Curves
Irregular
Number of individuals
Stable
Cyclic
Irruptive
Time
Fig. 9.7, p. 202
The Role of Predation in Controlling
Population Size
 Predator-prey cycles  Top-down control
 Bottom-up control
Population size (thousands)
160
140
Hare
120
Lynx
100
80
60
40
20
0
1845
1855
1865
1875
1885
1895
Year
1905
1915
1925
1935
Fig. 9.8, p. 203
Reproductive Patterns and Survival
 Asexual reproduction  r-selected species
 Sexual reproduction  K-selected species
K-Selected Species
elephant
r-Selected Species
saguaro
Fewer, larger offspring
High parental care and protection of offspring
Later reproductive age
Most offspring survive to reproductive age
Larger adults
Adapted to stable climate and environmental
conditions
Lower population growth rate (r)
Population size fairly stable and usually close
to carrying capacity (K)
Specialist niche
High ability to compete
Late successional species
cockroach
dandelion
Many small offspring
Little or no parental care and protection of
offspring
Early reproductive age
Most offspring die before reaching
reproductive age
Small adults
Adapted to unstable climate and environmental
conditions
High population growth rate (r)
Population size fluctuates wildly above and below
carrying capacity (K)
Generalist niche
Low ability to compete
Early successional species
Fig. 9.10b,
p. 205
Survivorship Curves
Percentage surviving (log scale)
100
10
1
0
Fig. 9.11, p. 206
Age
Human Impacts on Ecosystems
 Habitat degradation and fragmentation
 Ecosystem simplification
 Genetic resistance
 Predator elimination
 Introduction of non-native species
 Overharvesting renewable resources
 Interference with ecological systems
Environmental Stress
Organism Level
Population Level
Population Level
Physiological changes
Psychological changes
Behavior changes
Fewer or no offspring
Genetic defects
Birth defects
Cancers
Death
Change in population size
Change in age structure
(old, young, and weak may die)
Survival of strains genetically
resistant to stress
Loss of genetic diversity
and adaptability
Extinction
Disruption of energy flow through
food chains and webs
Disruption of biogeochemical cycles
Lower species diversity
Habitat loss or degradation
Less complex food webs
Lower stability
Ecosystem collapse
Fig. 9.12, p. 208
Key Concepts
 Factors affecting human population size
 Human population problems
 Managing population growth
Average crude birth rate
Average crude death rate
World
22
9
All developed
countries
11
10
All developing
countries
25
9
Developing
countries
(w/o China)
29
9
Fig. 11.2a, p. 239
Africa
38
14
Latin
America
24
6
Asia
22
8
Oceania
18
7
United
States
15
9
North
America
14
9
Europe
10
Fig. 11.2b, p. 239
11
Factors Affecting Human
Population Size
Population change equation
Population
Change
=
(Births + Immigration) – (Deaths + Emigration)
Zero population growth (ZPG)
Crude birth rate (BR)
Crude death rate (DR)
Refer to Fig. 11-2 p. 239
Natural Rate of Increase
Annual world
population growth
<1%
1-1.9%
2-2.9%
3+%
Data not
available
Fig. 11.3, p. 240
Asia
3.7 billion
4.7 billion
Europe
728 million
714 million
Africa
800 million
1.3 billion
Latin
America
518 million
703 million
North
America
306 million
374 million
Oceania
31 million
39 million
2000
2025
Fig. 11.6, p. 241
China
1.26 billion
1.4 billion
India
1 billion
1.4 billion
USA
Indonesia
Brazil
276 million
338 million
212 million
273 million
170 million
221 million
Pakistan
Russia
Bangladesh
Japan
151 million
227 million
145 million
137 million
128 million
177 million
127 million
121 million
Nigeria
123 million
205 million
Fig. 11.5, p. 241
2000
2025
Fertility Rates
 Replacement-level fertility  Total fertility rate (TFR)
Births per woman
<2
4-4.9
2-2.9
5+
3-3.9
No
Data
Fig. 11.8, p. 242
World
5 children per women
2.9
Developed
countries
2.5
1.5
Developing
countries
6.5
3.2
Africa
6.6
5.3
Latin
America
5.9
2.8
Asia
5.9
2.8
Oceania
3.8
2.4
North
America
3.5
2.0
Europe
2.6
1.4
Fig. 11.7, p. 241
1950
2000
The Demographic Transition
Stage 2
Transindustrial
Stage 3
Industrial
Stage 4
Postindustrial
High
80
70
Relative population size
Birth rate and death rate
(number per 1,000 per year)
Stage 1
Preindustrial
60
50
Birth rate
40
30
Death rate
20
10
0
Total population
Low
Increasing Growth Very high Decreasing
Low
Zero
growth rate
growth rate
growth rate growth rate growth rate growth rate
Low
Negative
growth rate
Fig. 11.26, p. 255
Time
Factors Affecting BR and TFR
 See bulleted list in text p. 243
Births per thousand population
 US BR’s and TFR’s
32
30
28
26
24
22
20
18
16 Demographic
transition Depression
14
0
1910
1920
1930
1940
World War II
Baby boom
1950
1960
Year
Baby bust Echo baby boom
1970
1980
1990
2000
2010
Fig. 11.11, p. 243
see Fig. 11-10 p. 243
12
11
Population (billion)
10
9
8
High
High
10.7
Medium
Low
Medium
8.9
7
6
Low
7.3
5
4
3
2
1950 1960 1970 1980 1990 2000 2010 2020 2030 2040
Year
2050
Fig. 11.9, p. 242
4.0
Births per woman
3.5
3.0
2.5
2.1
2.0
1.5
1.0
0.5
0
1920
1930
1940
1950
1960
1970
1980
1990
2000
2010
Year
Fig. 11.10, p. 243
Factors Affecting DR
 Life expectancy  Infant mortality rate (IMR)
Infant deaths
per 1,000 live births
<10
<10-35
<36-70
<71-100
<100+
Data not
available
Fig. 11.14, p. 246
Factors Affecting Natural Rate of
Increase
Rate of natural increase = crude birth rate = crude death rate
Rate per 1,000 people
50
Crude
birth rate
40
30
Rate of
natural
increase
20
Crude
death rate
Rate per 1,000 people
Developed Countries
50
Rate of
natural increase
40
Crude
birth rate
30
20
10
10
Year
Year
0
Developed Countries
Crude
death rate
0
Fig. 11.13, p. 245
Population Age Structure
Male
Female
Rapid Growth
Guatemala
Nigeria
Saudi Arabia
Ages 0-14
Slow Growth
United States
Australia
Canada
Ages 15-44
Zero Growth
Spain
Austria
Greece
Negative Growth
Germany
Bulgaria
Sweden
Ages 45-85+
Fig. 11.16a, p. 247
Solutions: Influencing
Population Size
Migration
Environmental refugees
Reducing births
Family planning
Empowerment of women
Economic rewards and penalties
Case Study: Slowing Population
Growth in India
Generally disappointing results:
Poor planning
Bureaucratic inefficiency
Low status of women
Extreme poverty
Lack of support
Case Study: Slowing Population
Growth in China
Generally positive results:
Economic incentives
Free medical care
Preferential treatment
Intrusive and coercive
Locally administered
Cutting Global Population Growth
Family planning
Reduce poverty
Elevate the status of women