chap 15- nature of communities

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  1. Communities
    • group of interacting species at same place and time
    • synergistics: interactions make communities into something more than the sum of parts
    • considered to be fundamental unit of landscape
    • often classified by physical or biological characteristics
  2. Subset of species used to define communities
    • Taxonomic affinity: "birds"
    • Guild: group of species using same resources "birds, bees, and bats are all pollen-eating animals"
    • Functional Group: includes species that function in a particular way but do not necessarily use the same resources misquetos and aphids
    • Food Web: based on trophic, energentic, interactions
  3. Food Web
    • organzed by tropic levels- group of species that have similar wayto obtain energy
    • primary producer: autotrophs
    • primary consumers: herbivores
    • secondary consumers: carnivores
    • tertiary consumers: carnivores
    • does not tell about strength of interaction
  4. Interaction Web
    • used to describe both trophic and non-trophic interactions among species
    • omnivores: feed on more than one trophic level
    • horitontal interactions: competition and positive interactions
  5. Community Structure
    • set of characteristics that shape a community
    • include species diversity and species composition
  6. Species Diversity
    • a measure that combines relative number of species to relative abundance
    • Shannon Index: calculated number showing diversity lowest 0 can go to infinity, the higher the value the more diversity
  7. Species richness
    number of species
  8. Species eveness
    tells commonness or rarity of species
  9. Biodiversity
    describe the diversity of important ecological entities that span multiple spatial scales, genes to species to communities
  10. Rank abundance curve
    plots proportional abundance of each species to the others in rank order from most to least abundant
  11. Species Accumulation Curve
    • calculated by plotting species richness as a function of the sampling effort
    • theoretically the more sampling done the line levels off revealing fewer or no new species
  12. Species Composition
    identity of the species present in the community
  13. Direct Interactions
    occur between 2 species and include trophic and non-trophic interactions
  14. Indirect Interactions
    relationship between 2 species is mediated by a 3rd or more species
  15. Trophic Cascade
    • rate of consumption at one level results in a change in species abundance or composition at lower trophic levels
    • kelp forest, urchins and otters
  16. Tropic Facilitation
    • consumer is indirectly facilitated by a positive interaction between its prey and another species,
    • juncus helped iva plant grow in turn helping aphid population
  17. Competitive Networks
    • competitive interactions among multiple species in which every species negatively interacts with every other species
    • circular web rather than linear
  18. Interaction Strength
    • effect of one species on the abundance of another
    • can be measured experimentally by removing one species(interactor species) from the community and looking at the effect on the other species(target species)
    • if removal of interactor resluts in large decrease in target species, interaction is strong and positive
    • if the abundance of the target increase the interactor species has srong negative effect
  19. Dominant Species
    • aka foundation species
    • large or abundant species or biomass in community, usually trees, provide habitat or food for other species
  20. Ecosystem Engineer
    are able to create. modify, or maintain physical habitat for themselves and other species
  21. Keystone Species
    • large effect on community not because of thier abundance but because of the roles they play
    • influence community structure indirectly , by trophic means
  22. Interactions are context-dependant
    changeable under different enviromental conditions
Card Set:
chap 15- nature of communities
2012-01-31 00:14:31
ecology communities

chapter 15 terms
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