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What is a community and its structure?
- - community - an association of interacting species inhabiting some defined area
- - community structure - includes number of species, relative abundance of species, and type of species
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Species diversity depends on...?
- Species evenness, and species richness
- Higher in more complex environments with many niches
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What does rank abundance curves show?
- Shows both components of species diversity - species evenness and richness
- Flatter rank abundance curve with lower slope indicates greater species evenness
- If comparing 2 species, the one that extends farther has greater species richness
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What does spatial heterogeneity do in an environment?
- Spatial heterogeneity can affect the coexistence of 2 or more species
- If nutrients are low in one place, but high in another, spatial heterogeneity can allow the species to coexist
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Alpha vs Beta diversity
- Alpha diversity - each community might have similar diversity within its boundaries
- Beta diversity - diversity may stay the same (alpha), but encounter new species
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Intermediate disturbance hypothesis
- Intermediate levels of disturbance promotes higher diversity
- Without disturbance, competitive exclusion operates
- With too much disturbance, only a few r-selected species with rapid colonization and life cycles inhabit
- Results in homogenization of communities, reducing beta diversity
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Food webs and trophic biology
- Trophic biology refers to the feeding relationships in communities
- Relationships are often depicted as food webs, which present feeding hierarchies as trophic levels
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Direct vs. Indirect Interactions
- Direct interactions involve effects of one species on another without the influence of a third (parasitism, herbivory, predation)
- Indirect - where one species affects another through a third species
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