Population Interactions PPT by ert554898

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									  Community Ecology


Interactions between populations
       Density dependent factors

 Operate as negative feedback mechanisms
 The population maintains a steady level
 Disease transmission
 Vulnerability to predators
 Food supply
 Over crowding
    What Controls Population Size and
             Growth Rate
•   Density-dependent factors:
    •   Intra-specific competition
         •   Food
         •   Space
    •   Contagious disease
    •   Waste production
    •   Inter specific competition
    •   Other species interactions
•   Density-independent factors:
    •   disturbance, environmental conditions
         •   Hurricanes
         •   Floods
         •   Colder than normal winter
Types of Interactions

     Competition

     Predator-Prey

      Mutualism

    Commensalism

      Parasitism
      Competition




Natural Selection minimizes competition!
                Competition:

 Iftwo species are competing, the growth of
  one population should reduce the size of the
  other
Predator-prey
                Predator-Prey Relationships

•   Prey defenses: avoid conflict!
    •   Coevolution
         •   as predator evolves, prey evolves to evade it
    •   Warning coloration and mimicry
    •   Camouflage
Predator-Prey Relationships

 •Predatorscan promote diversity by
  keeping competition in check
Idealized Predator-Prey Population Graph
            Predatory-Prey

If it is a predator-prey relationship, then the two
populations have opposite effects on one another
   Mutualism




 Both   species benefit
                     Mutualism

   If it is a mutually beneficial relationship, then the two
    populations increase each other’s size
               Commensalism
 One   species benefits, the other is unaffected
Is this mutualism or commensalism?
                Commensalism

   If the relationship is commensalistic, one species
    benefits (the commensal) and the other is unaffected
Parasitism
                Test you knowledge!
What type of relationship–?




   A coati eats tree fruit.

   Your dog has a flea

   You use a fast bicyclist to “draft” off of
         Carrying Capacity
The number of individuals that a habitat can support.

  If the population is a herbivore, K may depend
            on the population of plants
           Community Dynamics


Community: a group of populations (both plants and animals)
           that live together in a defined region.
                     Trophic Levels

      predator/        Eagles   4th trophic level
 tertiary consumer

     predator/         Foxes    3rd trophic level
secondary consumer

     herbivore/        Mice     2nd trophic level
 primary consumer

    autotroph/         Plants   1st trophic level
 primary producer
                Trophic Levels

                   Eagles   4th trophic level
if eagles go
extinct, what      Foxes    3rd trophic level
could happen
to…
foxes?
                   Mice     2nd trophic level
mice?
plants?            Plants   1st trophic level
                    Trophic Levels

                      Eagles   4th trophic level
If a new predator
on mice is
introduced, what      Foxes    3rd trophic level
could happen to…
mice?
                      Mice     2nd trophic level
plants?
foxes?
                      Plants   1st trophic level
eagles?
                Trophic Levels

                    Eagles   4th trophic level
If drought caused
a dip in plant
production, what    Foxes    3rd trophic level
would happen to…
mice?
                    Mice     2nd trophic level
foxes?
eagles?
                    Plants   1st trophic level
  Simplified Temperate Forest Food Web
What happens to when it’s a WEB instead of a CHAIN?

     Wolf                                      Eagle

                          Fox                Shrews

    Deer                Rabbit            Caterpillars


Oak seedling            Grasses               Herbs
               In long term, balance is restored
That is the end!

								
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