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Chapter 54.1-2 Community Ecology: The Interactions of Different Populations

Chapter 54.1-2 Community Ecology: The Interactions of Different Populations. I. What is a Community?. - An assemblage of species living close enough together for potential interaction. What forms the community structure?. II. Interspecific Interactions!.

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Chapter 54.1-2 Community Ecology: The Interactions of Different Populations

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  1. Chapter 54.1-2 Community Ecology: The Interactions of Different Populations I. What is a Community? - An assemblage of species living close enough together for potential interaction. What forms the community structure? II. Interspecific Interactions! - A competition for resources between individuals of two or more species when resources are in short supply; detrimental to both species (-/-) A. Competition ( - / - ) - Interaction detrimental to both species B. Competitive Exclusion Principle Two species with similar needs for same limiting resources cannot coexist in the same place. Example - Paramecium

  2. C. Ecological Niche • An organism’s role in the environment. • -Sum total of an organism’s use of abiotic/biotic resources in the environment. • -The Competitive Exclusion Principle can be restated to say that two species • cannot coexist in a community if their niches are identical. 1. Fundamental Niche -Niche that is possible for the organism due to abiotic conditions 2. Realized Niche - Niche that results due to biotic interactions D. Resource Partitioning -differentiation of niches that enables two similar species to coexist in a community. E. Character Displacement -the tendency for characteristics to be more divergent in sympatric populations of 2 species than allopatric populations of same 2 species

  3. Character Displacement(don’t focus on too much, will see again in evolution unit) -Allopatric means geographically separate; sympatric means geographically overlapping -both birds eat similarly sized seeds on Los Hermanos and Daphne islands. -Difference in beak morphology show adaptations that favor eating different-sized seeds

  4. F. Predation Types ( + / - ) 1) “Standard” ( + / - ) predator eats prey that is immediately consumed 2) Herbivory (+ / - ) animal eats plant predators live on (ectoparasite) /or in (endoparasite) a host and depend on the host for nutrition 3) Parasitism (+ / - ) 4) Parasitoidism (+ / - ) special type of parasitism where the parasite eventually kills the host http://www.youtube.com/watch?v=Df_iGe_JSzI G. Prey Defenses 1) Cryptic Coloration camouflage including deceptive markings. 2) Aposematic Coloration warning colors, that is sometimes associated with other defenses (toxins). 3) Batesian Mimicry harmless species mimics a harmful one 4) Mullerian Mimicry two or more unpalatable species resemble each other H. Symbiosis 1) Mutualism ( + / + ) two species benefit from their interaction 2) Commensalism ( + / 0 ) one species benefits from the interaction, but other is not affected. Vocab Quiz

  5. III. Species Diversity – 2 components -the variety of different kinds of organisms that make up the community A. Species Richness -the number of different species in the community B. Relative Abundance -the proportion each species represents of all individuals in the community H=0.71 H=1.39 -the higher the value H, the more diverse community C. Measure using Shannon diversity (H) -more resistant to invasive species (organism established outside native area), more resistant to disturbance/stress (drought, fire, flood), and are more productive (more biomass, meaning total mass of all organisms in a habitat) D. Diversity & Community Stability

  6. IV. Trophic Structure determines the feeding relationships between organisms A. Food Chains transfer of food energy from its source in photosynthetic organisms through herbivores and carnivores B. Food Webs All trophic relationships diagrammed in a community; interconnecting food chains

  7. C. Dominant Species -have the highest abundance or highest biomass (the sum weight of all individuals in a population) D. Keystone Species -exert an important regulating effect on other species in a community E. Ecosystem Engineers -an organism that influences community structure by causing physical changes to the environment Nellie the otter

  8. V. How is Community Structure controlled? N = minerals/nutrients V = vegetation H = herbivores P = predators A. Bottom-up model -unidirectional influence from lower to higher trophic levels N  V  H  P -predation controls community organization because predators limit herbivore numbers, which in turn control plant/phytoplankton numbers, which in turn control nutrient levels (aka trophic cascade model) B. Top-down model N  V  H  P

  9. Pygmy Seahorses Slide 3

  10. Slide 3

  11. Predator Interaction Slide 3

  12. Which community relationship is demonstrated by each of the pictures below? A: Commensalism B: Parasitoidism C: Mutualism D: Batesian Mimicry E: Mullerian Mimicry F: Cryptic Coloration I: G Herbivory H: Aposematic Coloration Batesian Mimicry Slide 3

  13. Gause’s experiment that led to idea of Competitive Exclusion

  14. Slide 1

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