Ecology of Populations
Chapter 46
Chapter Outline
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Scope of Ecology
Population Density and Distribution
Population Growth Models
Survivorship Curves
Age Distributions
Regulation of Population Size
Life History Patterns
Human Population Growth
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Environmental Impact
Scope of Ecology
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Ecology – what is it?
Definitions:
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Habitat - Place where an organism lives.
Population - All the organisms within an area
belonging to the same species.
Community - All various populations
interacting at same locale.
Ecosystem – A collection of communities
Ecological Levels
Density and Distribution
of Populations
 Population
Density - Number of
individuals per unit area or
volume.
 Population Distribution - Pattern
of dispersal of individuals within
the area of interest.
Uniform Distribution
Random Distribution
Clumped Distribution
Characteristics of Populations
 They
tend to grow
 Intrinsic Rate of Natural
Increase (r)
Population Growth Models
 Exponential
Growth
 Biotic Potential
 Environmental Resistance
Exponential Growth Curve
Logistic Growth
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Logistic growth—indicated by an S-shaped
curve
Difference between logistic and
exponential due to environmental
resistance
Logistic Growth
Carrying Capacity
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Carrying Capacity is the maximum number
of individuals of a given species the
environment can support.
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The closer the population to the carrying
capacity, the greater the environmental
resistance.
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Biotic potential is having full effect and birthrate is
a maximum during exponential growth.
St. Paul Island
Reindeer
Population
Mortality Patterns
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Cohort --- all the members of a population
born at the same time.
Survivorship---the probability of newborn
individuals of a cohort surviving to
particular ages.
Illustrated by Survivorship Curves
Survivorship Curves
Survivorship Curves
Age Distributions
 What
proportion of
population is in each
cohort?
 Age Structure Diagrams
U.S. Age Distributions
Regulation of Population Size
 Density
- Dependent Factors
 Density - Independent Factors
Factors That Affect
Population Size
Density Dependent Factors
1.
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2.
Competition
Intraspecific
Interspecific
Predation
3. Parasitism
4. Disease
Factors That Affect
Population Size
Density Independent Factors
1. Abiotic factors
2. Unpredictable,
catastrophic
events
Life History Patterns
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r - Strategists (Opportunistic)
 Remember
r=reproduction
Life History Patterns
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k - Strategists (Equilibrium)
 Remember
kapacity
k=Karrying
Human Population Growth
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Human population has had an exponential
growth pattern.
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Doubling time currently estimated at 53 years.
Population Size
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1800
1930
1960
2000
1
2
3
6
Billion
Billion
Billion
Billion
World Population Growth
Country Development
 More-Developed
Countries
(MDCs) GR=0.1%
 Less-Developed Countries
(LDCs) GR= 1.6%
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LDC population expected to
increase from 5-8b by 2050
Age Distributions
 Age
Structure Diagrams divide
populations into three age
groups.
 Pre-Reproductive
 Reproductive
 Post-Reproductive
The Demographic Transition
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Stage I: high birthrates and death rates
Stage II: continued high birthrates,
declining death rates
Stage III: falling birthrates and death
rates, eventually stabilizing
More-Developed Countries
Less-Developed Countries
Age Distribution of the World’s
Population
Population Structures by Age and Sex, 2005
Millions
Less Developed
Regions
More Developed
Regions
Age
Male
300 200 100
Female
0
100 200 300
80+
75-79
70-74
65-69
60-64
55-59
50-54
45-49
40-44
35-39
30-34
25-29
20-24
17-19
10-16
5-9
0-4
Male
300
Female
100
100
300
Source: United Nations, World Population Prospects: The 2002 Revision (medium scenario), 2003.
Figure 7.2 World Population
Distribution by Region, 1998
and 2050
Environmental Impact
 Measured
in terms of:
 Population Size
 Resource Consumption Per
Capita
 Resultant Pollution
Environmental Impact
Review
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Scope of Ecology
Population Density and Distribution
Population Growth Models
Survivorship Curves
Age Distributions
Regulation of Population Size
Life History Patterns
Human Population Growth
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Environmental Impact