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					             Ecology

          Part 4. Populations
         Part 5. Communities
Part 6. Biodiversity and Conservation
Population Ecology: Population Growth Models

           Population Limiting Factors
  • Population growth models
      – Logistic Growth Model
           • Often called the S-shaped growth curve
           • Occurs when a population’s growth slows or stops
             following exponential growth.
           • Growth stops at the population’s carrying capacity
           • Populations stop increasing when:
               – Birth rate is less than death rate
                 (Birth rate < Death rate)
               – Emigration exceeds Immigration
                 (Emigration > Immigration)
Population Ecology: Population Growth Models

           Population Limiting Factors
  •     Population growth models
      – Logistic Growth Model
           The S-curve is not as pretty as the image looks
           1. Carrying capacity can be raised or lowered. How?
               Example 1: Artificial fertilizers have raised k
               Example 2: Decreased habitat can lower k
           2. Populations don’t reach k as smoothly as in the logistic
              graph.
               •   Boom-and-Bust Cycles
               •   Predator-Prey Cycles
Community Ecology: Communities

                         Communities
  • Review:
      – A community is a group of interacting populations
        that occupy the same area at the same time.
Community Ecology: Communities

                         Communities
  • Limiting Factors
      – Any abiotic or biotic factor that restricts the
        numbers, reproduction, or distribution of
        organisms.
Community Ecology: Communities

                         Communities
  • Range of Tolerance
      – The limits within which an organism can exist.
Community Ecology: Ecological Succession

                  Ecological Succession
  • Ecological Succession
      – The change in an ecosystem that happens when
        one community replaces another as a result of
        changing biotic and abiotic factors
Community Ecology: Ecological Succession

                  Ecological Succession
  • Ecological Succession
      – Consists of 2 types:
           • Primary Succession
           • Secondary Succession
Community Ecology: Ecological Succession: Primary Succession

                  Ecological Succession
  • Ecological Succession: Primary
      – The establishment of a community in an area of
        exposed rock that does not have topsoil is called
        Primary Succession.
           • It occurs very slowly at first
Community Ecology: Ecological Succession: Primary Succession

                  Ecological Succession
  • Ecological Succession: Primary
      – The first organisms to arrive are usually lichens or
        mosses, which are called pioneer species.
           • They secrete acids that can break down rock
           • Their dead, decaying organic materials, along with bits
             of sediment from the rock make up soil.
Community Ecology: Ecological Succession: Primary Succession

                  Ecological Succession
  • Ecological Succession: Primary
      – Small weedy plants and other organisms become
        established.
      – As these organisms die, additional soil is created
Community Ecology: Ecological Succession: Primary Succession

                  Ecological Succession
  • Ecological Succession: Primary
      – Seeds brought in by animals, water and wind
        begin to grow in the soil.
      – Eventually enough soil is present for shrubs and
        trees to grow.
Community Ecology: Ecological Succession: Primary Succession

                  Ecological Succession
  • Ecological Succession: Primary
      – The stable, mature community that eventually
        develops from bare rock
        is called a
        climax community.
Community Ecology: Ecological Succession: Secondary Succession

                  Ecological Succession
  • Ecological Succession: Secondary
      – Disturbances (fire, flood, windstorms) can disrupt
        a community.
      – After a disturbance,
        new species of plants
        and animals might
        occupy the habitat.
Community Ecology: Ecological Succession: Secondary Succession

                  Ecological Succession
  • Ecological Succession: Secondary
      – Pioneer species in secondary succession are
        usually plants that begin to grow in the disturbed
        area.
      – This is much faster
        than primary
        succession
Community Ecology: Ecological Succession

                  Ecological Succession
  • Ecological Succession: End point?
      – Cannot be predicted
      – Different rates of growth &
        human involvement
        make it impossible to
        know if a true climax
        community has been
        reached.
Biodiversity and Conservation: Introduction


         On the left side of your IntNB,
            address the following:
  • What would happen if all of the jackrabbits in
    a food web died suddenly?

  • Is the disappearance of one species from
    Earth important, or will another species fill its
    niche?
Biodiversity and Conservation: What is biodiversity?


                               Biodiversity
  • What is Biodiversity?
    The variety of life in an area that is
    determined by the number of different
    species in that area.
  • There are 2 main types:




        Genetic Diversity                              Species Diversity
Biodiversity and Conservation: Why is biodiversity important?

                           Biodiversity




                                                                Penicillin: Derived from
                                                                      bread mold



     Teosinte: A             Domestic corn
   distant relative             plant
       of corn


                                                        Madagascar Periwinkle: Used to
                                                       treat childhood forms of leukemia
Biodiversity and Conservation: Extinctions

                          Extinction Rates
  • The gradual process of becoming extinct is
    known as background extinction.
  • Mass extinctions: When a large percentage of
    all living species become extinct in a relatively
    short period of time.
  • 250 MYA: Over
    90% of species
    died
 Biodiversity and Conservation: Extinctions

       Estimated number of Extinctions since
                     1600
Group            Main-    Island      Ocean   Total   Approximate    Percent of
                 land                                 Number of      Group
                                                      Species        Extinct
Mammals            30        51          4       85        4000          2.1

Birds              21        92          0      113        9000          1.3

Reptiles            1        20          0       21        6300          0.3

Amphibians          2         0          0        2        4200         0.05

Fish               22         1          0       23       19,100         0.1

Invertebrates      49        48          1       98     1,000,000+      0.01

Flowering         245        139         0      384      250,000         0.2
Plants
Biodiversity and Conservation: Extinctions

       Five Most Recent Mass Extinctions


  Cretaceous Period (65 MYA)

  Triassic Period (200 MYA)


  Permian Period (250 MYA)


   Devonian Period (360 MYA)



   Ordovician Period (444 MYA)
  Activity: Understanding Geological
                Time
• Working in your groups, you will get the
  following supplies:
  – A meter stick
  – A roll of 5 meters of paper
  – Colored pencils
• Using the worksheet, plot out the dates.
  – 1 million years is a millimeter
  – 1 billion years is a meter

				
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posted:11/26/2011
language:English
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