Lecture 9 Communities C

Lecture 9 Communities C - Species diversity two components...

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2/17/09 1 III. SPECIES DIVERSITY Species diversity : two components Species richness (number of species) Relative abundance of species (evenness) Certain species - large impact on the structure of entire communities *highly abundant *play a pivotal role Dominant species most abundant or have the highest biomass Redwood forest Keystone species – Usually not most abundant – Influence community by their ecological niches
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2/17/09 2 Sea stars ( Pisaster ochraceous ) - keystone species Why would species diversity in the intertidal decrease when Pisaster was removed? a. Pisaster was a superior competitor b. Pisaster predation kept superior competitors in check c. Competitive exclusion d. Resource partitioning Mytilus californicus (mussel) Pisaster ochraceous (sea star) Foundation Species - Ecosystem “Engineers” Some organisms exert their influence by causing physical changes in the environment IV. TROPHIC STRUCTURE the feeding relationships between organisms in a community (what you eat and who eats you)
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  • Spring '08
  • SCHROEDER
  • trophic level, Apex predator, Trophic relationships, IV. TROPHIC STRUCTURE, complex trophic interactions

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Lecture 9 Communities C - Species diversity two components...

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