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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.
•“Trade-offs” and Life Histories
Semelparity



      Harsh, unpredictable
      environment.
     Factors That Influence
   Life Histories: “Trade offs”

•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
   •Linked Populations
   •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
  populations linked by immigration and
  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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