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```									BIOLOGY 1407 - CHAPTER 53

POPULATION ECOLOGY
Figure 52.0 Monarch butterflies
POPULATION ECOLOGY

•Population Ecology

•Population

•Population Characteristics

•Population Dynamics
Population Dynamics

•Characteristics of Dynamics
•Size
•Density
•Dispersal
•Immigration
•Emigration
•Births
•Deaths
•Survivorship
MEASURING DENSITY

Density – Number of individuals per unit
of area.
•Determination of Density
•Counting Individuals
•Estimates By Counting Individuals
•Estimates By Indirect Indicators
•Mark-recapture Method

N = (Number Marked) X (Catch Second Time)
Number Of Marked Recaptures
PATTERN OF DISPERSION

UNIFORM   CLUMPED   RANDOM
Fig. 53-4

(a) Clumped

(b) Uniform

(c) Random
Clumped Dispersion
Uniform and Random Dispersion

Random

Uniform
DEMOGRAPHY
The study of the vital statistics of a population
and how they change over time. Factors that
influence population density and dispersion
patterns.
•The Birth And Death Rates Of A
Population. (Vital Statistics)
•Age Structure - Relative Number
Of Individuals Of Each Age In The
Population.
•Generation Time
•Sex Ratio
LIFE TABLES
Life Tables – Age specific summary
of the survival pattern of a population.
Describe how birth rates and death rates
vary with age over a time period
corresponding to the maximum life span.
Look at cohorts, a group of individuals of
the same age.
SURVIVORSHIP CURVES
Plots the number or percentage of a
cohort alive at each age.

Plot Of The Numbers In A Cohort
Still Alive At Each Age.
Type I
Type II
Type III
Survivorship Data for Male and
Female Belding’s Ground Squirrel
SURVIVORSHIP CURVES
LIFE HISTORY

The traits that affect an organism’s
schedule of reproduction and death.

•Semelparity – One large reproductive effort.
•Often found in harsh, unfavorable
environments.
•Interoparity – Repeated reproductive efforts.
•More common in more stable, more
favorable environments.
Semelparity

Harsh, unpredictable
environment.
Factors That Influence

•Allocation Of Limited Resources
•Cost of Parental Care
•Benefits of Parental Care
•Size of Propagule (Reproductive unit) and
Number Produced
•Age Of First Reproduction
Fig. 53-8

RESULTS

Parents surviving the following winter (%)   100
Male
Female
80

60

40

20

0
Reduced         Normal       Enlarged
brood size      brood size   brood size
Many vs. Few

Many very small seed.

A few very large seed
POPULATION GROWTH
Intrinsic rate of increase - maximum
population growth that occurs
under ideal conditions with
unlimited resources.
Change in population size in a time
interval may be shown as:
∆N/∆t = B - D
Based on percapita birth and death rates
∆N/∆t = bN - mN
POPULATION GROWTH RATE
Exponential Model
•Describes idealized growth rate.
•Describes a growing population
that will double in size.

70/Growth Rate = Doubling Time

•J SHAPED GROWTH CURVE
Growth Prediction From
Exponential Model

Two Different rmax Values
Example of Exponential Growth

Kruger National Park, South Africa
POPULATION GROWTH RATE

LOGISTIC GROWTH RATE
Assumes that the rate of population
growth slows as the population size
approaches carrying capacity, leveling
to a constant level. S-shaped curve

CARRYING CAPACITY
The maximum sustainable population
a particular environment can support
over a long period of time.
Figure 52.11 Population growth predicted by the logistic model
Logistic Models

Stable Population

Seasonal Increase

Severe Environmental Impact
POPULATION GROWTH RATE

K -SELECTED POPULATION - EQUILIBRIUM
POPULATION – Favored at high density,
influenced by density dependent
selection.
r - SELECTED POPULATION - OPPORTUNISTIC
POPULATION – Favored at low density,
density independent selection.
Density Dependent
Growth Factors

•Territoriality
•Disease/Health
•Predation
•Competition
•Toxic Waste
•Intrinsic Factors
Fig. 53-17

(a) Cheetah marking its territory

(b) Gannets
Figure 53.17f
Fig. 53-16

Percentage of juveniles producing lambs   100

80

60

40

20

0
200   300       400         500   600
Population size
Density Independent
Factors
•Catastrophes
•Weather - Hot, Cold, Dry
•Extremes
•Natural in Many Species

Mixed Density Dependent and
Density Independent Interactions
Population Dynamics
Interactions Between Biotic and Abiotic

•Stability And Fluctuations
•Large Animals - Moose
•Small Animals – Dungeness Crabs

•Metapopulations and Immigration
•Isolated Populations

•Population Cycles
•Lemmings – 3-4 Years
•10 Year Snowshoe Hare/Lynx
Dungeness Crabs
Fig. 53-19

50                                          2,500
Wolves           Moose
Number of wolves

Number of moose
40                                          2,000

30                                          1,500

20                                          1,000

10                                          500

0                                           0
1955   1965   1975       1985    1995   2005
Year
Immigration, Emigration, and
Metapopulations
• Metapopulations are groups of
emigration
• High levels of immigration combined with
higher survival can result in greater
stability in populations
Fig. 53-21

˚
Aland
Islands
EUROPE

Occupied patch
5 km   Unoccupied patch
Fig. 53-20

Snowshoe hare
160
Number of hares

Number of lynx
(thousands)
120
(thousands)

9
Lynx
80
6

40                                          3

0                                          0
1850    1875          1900      1925
Year
POPULATION CYCLES

HUMAN POPULATION
1650 - 500,000,000
1850 - ONE BILLION
1930 - TWO BILLION
1975 - FOUR BILLION
2017 - EIGHT BILLION
Human Population Growth
Figure 53.23

2.2

2.0

1.8

1.6
Annual percent increase

1.4
2009
1.2
Projected
1.0                                 data
0.8

0.6

0.4

0.2

0
1950   1975   2000     2025         2050
Year
Fig. 53-25

Rapid growth                         Slow growth                       No growth
Afghanistan                         United States                        Italy
Male     Female          Age        Male      Female       Age       Male       Female
85+                               85+
80–84                            80–84
75–79                            75–79
70–74                            70–74
65–69                            65–69
60–64                            60–64
55–59                            55–59
50–54                            50–54
45–49                            45–49
40–44                            40–44
35–39                            35–39
30–34                            30–34
25–29                            25–29
20–24                            20–24
15–19                            15–19
10–14                            10–14
5–9                               5–9
0–4                               0–4
10 8        6 4 2 0 2 4 6           8 10    8   6 4 2 0 2 4 6           8     8   6 4 2 0 2 4 6 8
Percent of population               Percent of population             Percent of population
Infant Mortality/Life Expectancy
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
Global Carrying Capacity
•Average estimates of 10 to 15 billion
•Leeuwenhoek – 13.4 Billion - 1679
•Estimates from one trillion to one billion
•Very difficult to predict
•Ecological footprint
•Approximately 1.7 Hectares/Person
•Average US Ecological Footprint – 10 Hectares
•Ecological Capacity – Footprint to Available
Capacity – US – 10/6.2 ha/person
Fig. 53-27

Log (g carbon/year)
13.4
9.8
5.8
Not analyzed
• Our carrying capacity could potentially be
limited by food, space, nonrenewable
resources, or buildup of wastes

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