Overview Ch 13,14,

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Overview Ch 13,14, 15 Intro to relationships

•     tropic                        non tropic
  interactions     herbivory                  
  Commensalism    grazing browsing   
  competition     frugivory                   
  Amensalism     seed predation          
  neutralism     predation                   
  Mutualsim     parasitism                  
  Mycorrhizae    saprobism                  
  Pollination

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Definitions of terms applying to relationships

•      Trophic terms hebivory, (know terms from
  video), carnivore, omnivore
•                     
• parasitism   - 1 benefits (P) 1 is harmed (host)
• competition  - both species are harmed, fewer
  resources  
• predation   - 1 benefits (predator) 1 is harmed
  (prey)
• saprobism    - eating dead material no
  impact      

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Definitions cont

• Amensalism A symbiotic relationship between
  organisms in which one species is harmed or
  inhibited and the other species is unaffected.-
• Mutualism - Both species benefit by the
  interaction between the two species.
• Ex. Pollination
• Commensalism - at table together'. This is a
  symbiotic relationship between two species in
  which one species benefits and the has no effect.
• neutralism - 2 species exist in same area with
  no impact on each other

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Introduction to relationships

•  Haskells Gain-Loss Matrix
•               Effect on weak species
•                                             
  -                        0                      
   
• effect on                      -   
  competition         amensalism         
  parasitism
• strong species           0    amensalism        
  neutralism           commensalism
                                  
  Predation            commensalism     mutualism
  

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Competition Chapter 13
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Modes of Competition

• Interference
• Direct aggressive interaction between
  individuals.
• Intraspecific
• Competition with members of own species.
• Interspecific
• Competition between individuals of two species -
  reduces fitness of both.

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Types of competition cont

• Scramble -Food resources
• Contest
• Head to head battles
• Mates
• Territory
• Physical contest, visual, odor cues

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Interspecific Competition Among Herbaceous Plants

• Self-Thinning
• Plant growth rates and weights have been found to
  increase in low density populations.
• Competition is more intense at higher pop
  densities.
• mortality among competing plants.

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Interspecific Competition Among Herbaceous Plants
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Lotka Volterra

• In general, LV predicts coexistence of two
  species when, for both species, interspecific
  competition is weaker than intraspecific
  competition.
• Predict population growth for the two species
  will stop when
• N1K 1-?12 N2 and N2 K 2- ?21 N1
• Zero Growth Isoclines
• Above Population increasing
• Below Population decreasing
• Coexistence of two species is only possible when
  isoclines cross.

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Lotka Volterra

• Effect of interspecific competition on population
  growth of each species
• dN1 / dt rm1N1 ((K1-N1-?12N2) / K1)
• dN2 / dt rm2N2 ((K2-N2-?21N1) / K2)
• ?12 Effect of individual of species 2 on rate
  of pop. growth of species 1.
• ?21 Effect of individual of species 1 on rate
  of pop. growth of species 2.

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Lotka Volterra
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Niches

• Niche Summarizes environmental factors that
  influence growth, survival, and reproduction of a
  species.
• Type of food eaten, area it lives in.

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Niches

• Hutchinson defined niche as
• n-dimensional hyper-volume
• n equates the number of environmental factors
  important to survival and reproduction of a
  species.
• Fundamental niche hypervolume many env
  factors considered such as food, nest sites,
  mating strategies.
• Realized niche (also called ecological niche)
  includes interactions such as competition that
  may restrict environments where a species may
  live.
• Includes inter and intra specific competition

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Feeding Niches of Galapagos Finches

• Grant found differences in beak size among ground
  finches translates directly into diet.
• Size of seeds eaten can be estimated by measuring
  beak depths.
• Individuals with deepest beaks fed on hardest
  seeds.
• After 1977 drought, the remaining seeds were
  very hard. Thus, mortality was most heavy in
  birds with smaller beaks.

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Feeding Niches of Galapagos Finches
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Gause Principle of Competitive Exclusion
Pileated Downy Northern Flicker

• Two species with identical niches cannot coexist
  indefinitely.
• One will be a better competitor and thus have
  higher fitness and eventually exclude the other.
• 4 C rule (Complete Competitors Cannot Coexist
• Compare niches of 5 species of woodpeckers

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Paramecia Lab Experiments

• Gause demonstrated resource limitation with
  Paramecium caudatum and Paramecium aurelia in
  presence of two different concentrations of
  Bacillus pyocyaneus.
• When grown alone, carrying capacity determined by
  intraspecific competition.
• When grown together, P. caudatum quickly
  declined.
• Reduced resource supplies increased competition.

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Paramecia Lab Experiments
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Competition and Niches

• Competition can restrict species to their
  realized niches.
• But if competitive interactions are strong and
  pervasive enough, they may produce an
  evolutionary response in the competitor
  population.
• Changes fundamental niche.

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Niche Overlap and Competition Between Barnacles

• Connell discovered interspecific competition in
  barnacles. Balanus plays a role in determining
  lower limit of Chthamalus within intertidal zone.
• Did not account for all observed patterns.
• Predation by starfish

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Competition and Niches of Small Rodents

• Brown studied competition among rodents in
  Chihuahuan Desert.
• Predicted if competition among rodents is mainly
  for food, then small granivorous rodent
  populations would increase in response to removal
  of larger granivorous rodents.
• Insectivorous rodents would show little or no
  response.
• Results supported hypothesis.

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Competition and Niches of Small Rodents
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Character Displacement resource partitioning

• degree of competition depends on degree of niche
  overlap, interspecific competition is predicted
  to lead to directional selection for reduced
  niche overlap.
• Resource Partioning ex. beaks of finches
• Compare 5 types of beaks in Darwins finches

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Character Displacement