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Population Ecology - Download Now PowerPoint

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									Population Ecology
              Population
                                   single
Def. a group of individuals of a __________
   species living in the same area
Characteristics of a popl’n
1) Size
2) Density
3) Dispersion
4) Age Structure
Dynamic Population Pyramid
US vs. Swaziland
                  Measuring Density
  Mark and Recapture Method
                              4                   1
                                         =
                              3                   x
                                       4x = 3
              5                         x = 4/3
    4

                                                  x

          3                                  1


  How would you find the value of x?     Set up a proportion

Apply same strategy of proportion for mark and recapture method
         Mark and Recapture
40 fish are marked,
  captured and            # of recaptures in
                          2nd catch                    # of captures
  released. In 2nd                             =
                          Total in 2nd catch           Total Popl’n (N)
  capture, 45 fish are
  caught, 9 of which
  were marked                       9                        40
                                                   =
  (recaptured) What is              45                       N
  the estimated number                         9N = 1800
  of individuals in the                         N = 200
  population?
              Demography
Def. The study of factors that affect the
 growth and decline of populations.

Factors that affect growth: Birth and Immigration
Factors that affect decline: Death and Emmigration
        Survivorship Curves
Describe how mortality of individuals in a
 species vary over time; gives survival
 pattern of popl’ns        Type I: most
                           survive to middle
                            Type III:constant
                            Type II: most
                           age before
                            individuals die
                            death rate;
                           mortality rates
                            while still young;
                            likelihood of
                           increase; fewdeath
                            few survive toages
                            is equal (high
                           offspringat all care
                            reproductive age
                           of young)
                Life Histories
Characteristics that describe an organism’s
   survival and reproductive schedule
1. Big Bang Reproduction / Semelparity
     Ex. Salmon Spawning
     • Lower rate of offspring survival
     • Unpredictable env’ts
2. Repeated Reproduction / Interoparity
     Ex. Lizards, humans
     • Higher rate of offspring survival
     • More dependable env’ts w/ limited resources
   Population Growth Models
2 Models

  1) Exponential Growth Model

  2) Logistical Growth Models
What population do you think this is?
    Exponential Growth Model
1) Also called geometric growth or J-
   shaped growth.
2) 1st growth phase is slow (lag phase)
3) 2nd growth phase is rapid (the
   exponential phase)
 So, what do you think is going to
 happen to the human population?
• We will probably reach our carrying
  capacity.
• Our growth rate will start to look like most
  organisms, which is the Logistic Growth
  Model           Carrying Capacity (k)




                               What letter does this curve
                                   kind of look like?
          Logistical Growth Model
1) Often called the S-shaped growth curve
2) Growth slows or stops following exponential growth
   at the population’s carrying capacity
3) Populations stop increasing when:
     •   Birth rate < Death rate
     •   Emigration > Immigration
4) Carrying capacity can be raised or lowered. How?
     •   Ex. 1: Artificial fertilizers have raised k
     •   Ex. 2: Decreased habitat can lower k
    Deriving Equations to Growth
              Models
We will now derive the mathematical equations for
  both models
First let’s define some variables:

N = Population size
K = Carrying capacity
T = time
r = reproductive rate
B = # of births
D = # of deaths

								
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