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Community Ecology Chapter 54
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Interspecific Interactions Competition --/-- Competitive exclusion Ecological Niches (Habitat-address; niche- profession) Resource partitioning-allows similar species to coexist in a community Fundamental niche-potential Realized niche-actual-may be result of interspecific competition
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Character Displacement Tendency for characteristics to diverge more in sympatric pop of 2 species than in allopatric pop
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Predation +/-- Can be animal eating plant tissues Defensive adaptations –Cryptic coloration
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Aposematic coloration- warning
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Batesian mimicry-harmless or palative looks bad
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Mullerian mimicry 2 unpalatable species look alike
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Herbivory +/-- Plants have chemical toxins, spines, thorns ex strychnine, nicotine, selenium toxins Herbivores-special adaptations –Insect-chemical sensors –Sense of smell –Specialized teeth –Length of digestive systems
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Symbiosis Parasitism +/-- Mutualism +/+ obligate; facultative Commensalism +/0
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Species Diversity Species richness Relative abundance
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Shannon diversity (H) Index based on species richness and relative abundance
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Trophic structure Food Chain
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Food Webs (Elton 1920s)
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Limits on length of food chain Energetic hypothesis-inefficiency of energy transfer -10% rule Dynamic stability hypothesis-long food chains are less stable than short ones- population fluctuations at lower trophic levels are magnified at higher levels Also-carnivores tend to be larger at successive trophic levels-can’t get enough food to meet needs
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Dominant species Most abundant-have the highest biomass Exert a powerful control Are they are competitively superior in exploiting limited resources? Are they are most successful at avoiding predation?-would explain effect of invasive species…
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Invasive pressure American Chestnut Before 1910-40% of US trees-fungal disease- Chestnut blight-killed all the trees-oak, hickory replaced; mammals, birds ok, but 7 species of moths and butterflies became extinct
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Keystone species
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Foundation species Ecosystem “engineers” Affect by causing physical changes in the environment Ex beavers Facilitators-may help other species
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Models of organization Bottom upV H N V H P Top down V H N V H P Trophic Cascade Biomanipulation-prevent algal blooms by adding consumers rather than chemicals
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Disturbance Influences species diversity and composition Storms, waves, fires, freezing, drought, Moderate disturbance can foster greater diversity than low or high levels
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Ecological succession Species are replaced by other species Primary Secondary Climax community
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Island Equilibrium Model
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Detritivores Return nutrients to the soil Law of conservation of mass
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Aquatic Ecosystem Light limitation Nutrient limitation Eutrophication
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Biomass-dry mass
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Phytoplankton continually replace their biomass at such a rapid rate, they can support a biomass of zooplankton bigger than their own biomass.
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The Green World Hypothesis Terrestrial herbivores are held in check by a variety of factors.
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Transitional Page
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Productivity GPP-gross primary production NPP-net primary production NPP=GPP – R(autotrophic respiration) Primary production –in aquatic is mostly affected by light and nutrients-N and P –Eutrophic-nutrient rich –On land-temp and water –evotranspiration
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Biogeochemical cycles
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Nitrogen cycle
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Additional Terms Bioremediation-use of organisms to detoxify polluted areas Bioaugmentation-add desirable species such as nitrogen fixers Biodiversity (3 Levels)-genetic diversity, species diversity and ecosystem diversity Threats: habitat loss, introduced species, over-harvesting, global change
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Population conservation Focuses on: –Population size –Genetic diversity –Critical habitat
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MVP Minimum Viable Population Extinction Vortex
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Landscape and regional conservation Habitat fragmentation Movement corridors Biodiversity hot spot-small area with an exceptional concentration of endemic species
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Human Actions Agriculture-nutrient cycling-take it out of soil or too much in water Acid precipitation Biological magnification Greenhouse effect Global warming Ozone layer
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Elements www.animationfactory.com
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