Chapter 53:Community ecology

  1. what is a community?
    • interacting species, usually living within a defined area
    • ex.2 species interacting
  2. interactions among species have two main outcomes:
    • 1.they affect thr distribution and abundance of the inetracting species
    • 2.they are agents of natural selection
  3. competition
    occurs when individuals use the same resoruces, resulting in lower fitness(-/-)
  4. Mutualism
    when two species interact in a way that confers fitness to both (+/+)
  5. Commensalism
    occurs when one species but the other species is unaffected (+/0)..The least studied
  6. Predation
    One organism eats another, increasing the predators fitness but decreases the prey(+/-)
  7. Herbivory
    animal eats plant. (+/-)
  8. Intraspecific Competition
    • competition that occurs between memebers of the same species
    • -Occurs when the niches of two species overlap
  9. Interspecific Competition
    • occurs when individuals from different species use the same limiting resources
    • ex. the barnacles>>>>Chthamalus(high tidal area); Balanus(low tidal area); Balanus outcompetes Chthamalus from coming down
  10. Niche
    the range of resources that the species is abe to use or the range of conditions it can tolerate
  11. Competitive exclusion principle
    Not possible for species with the same niche to coexist
  12. asymmetric competition
    one species suffers a much greater fitness decline than the other species does
  13. Symmetric competition
    each of the interacting species experiences a roughly equal decrease in fitness
  14. Fundamental niche
    • the combination of resources or areas used or conditions tolerated in the absence of predators
    • -always larger larger than the realized
  15. Realized niched
    the portion of resoruces or areas used or conditions tolerated when competition occurs
  16. Niche differentiaition(resource partitioning)
    • an evolutionary change in resource use, caused by competition.
    • ex.if 2 species compete over a resource(middle part), then overtime they would grow apart so they would not be competing(no more middle part would remain in the ven diagram)
  17. Character displacement:
    • the change that occurs in species traits, and that allows individuals to exploit different resources
    • Ex. Galapagos Finches
  18. Mullerian mimicry
    when harmful species resemble each other
  19. Batesian mimicry
    when non-harmful species resemble harmful species
  20. Inducible defenses
    defensive traits that are produced only in response to the presence of a predator
  21. Disturbance
    any event that removes biomass from a comunnity
  22. Primary succession
    when a disturbance removes the soil and its organism. Ex.Glaciers, floods, volcanic eruptions
  23. Secondary succession
    • when a disturbance removes some or all organism but leaves the soil intact.
    • ex.Fires
  24. what are early successional communties dominated by?
    early successional communties are dominated by species that are short-lived and small in stature
  25. What are late successional communites dominated by?
    Late successional communities are dominated by species that tend to be long-lived, large and good competitiors for light and nutrients
  26. Pioneer species
    tend to have "weedy" life histories. adapted for growth in distrubed soils
  27. Facilitation
    early species makes condtions more favorable for the next species. Shade/nutrients
  28. Tolerance
    existing species do not affect how the new species establishes
  29. Inhibition
    one species inhibits the establishment of another
  30. Species richness
    how many species are present in a given community
  31. Species diversity
    • incorporates the number of species in an area and also their relative abundance
    • -(How common or how rare compared to other species) Eveness
  32. species richeness should be higher on
    1.larger islands2.nearshore islands
  33. Intermediate distrubance hypothesis:
    the region with a moderate type, frequency, and severity of disturbance should have high species richness and diversity
  34. What is niche differentiation?
    -the evolution of traits that reduce niche overlap and competiton
  35. why are inducible defenses advantageous?
    -they make efficient use of resources, because they are produced only when needed
  36. Species diversity is correlated with
    • 1.latitude
    • 2.productivity
    • 3.island size
  37. What is net primary productivity?
    -the amount of energy that is stored in standing biomass per year
  38. top-down control
    herbivore populations are kept at relatively low levels by predation and disease
  39. Bottom-up control
    plant matter is low in nitrogen or defended by chemicals that are toxic to herbivores
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Chapter 53:Community ecology