Community Ecology Chapter 54. Interspecific Interactions Competition --/-- Competitive exclusion...
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Transcript of Community Ecology Chapter 54. Interspecific Interactions Competition --/-- Competitive exclusion...
Community EcologyChapter 54
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
Character Displacement• Tendency for characteristics to
diverge more in sympatric pop of 2 species than in allopatric pop
Predation +/--• Can be animal eating plant tissues• Defensive adaptations
– Cryptic coloration
Aposematic coloration-warning
Batesian mimicry-harmless or palative looks bad
Mullerian mimicry• 2 unpalatable species look alike
Herbivory +/--
Plants have chemical toxins, spines, thorns
ex strychnine, nicotine, selenium toxinsHerbivores-special adaptations
– Insect-chemical sensors– Sense of smell– Specialized teeth– Length of digestive systems
Symbiosis• Parasitism +/--• Mutualism +/+ obligate; facultative• Commensalism +/0
Facilitation• Species can have positive effects on
the survival and reproduction of another species without living in direct or intimate contact.
• Ex. Juncus grows in salt marshes and prevents salt buildup-benefits other species
Species Diversity• Species richness• Relative abundance
Shannon diversity (H)• Index based on species richness and
relative abundance
Trophic structure• Food Chain
Food Webs (Elton 1920s)
Limits on length of foodchain
• 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
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…
Invasive pressure• American Chestnut• Before 1910-40% of US trees-fungal disease-Chestnut blight-killed all the trees-oak, hickoryreplaced; mammals, birdsok, but 7 species of moths and butterfliesbecame extinct
Keystone species• Sea otters: Sea otters are a keystone species in the kelp
forests. They eat many invertebrates, but especially sea urchins. If there are too many sea urchins, they will eat too much of the kelp and destroy it.
• Elephants: By eating small trees, elephants preserve the grasslands, because the grasses need plenty of sun to survive. If they were not there, the savanna would convert to a forest or scrublands.
• Grizzly bears: As predators, bears keep down the numbers of several species, like moose and elk. They also carry and deposit seeds throughout the ecosystem. Bears that eat salmon will leave their dropping and the partially eaten remains that provide nutrients such as sulfur, nitrogen and carbon to the soil.
Foundation species• Ecosystem “engineers”• Affect by causing physical changes in
the environment• Ex beavers• Facilitators-may help other species
Models of organization• Bottom up VH increase of veg-more
H• NVHP• Top down VH increase in H- less V• NVHP Trophic Cascade (ex.
Remove top carnivoresprimary carnivores so upherbivores decreasephytoplankton goes upnutrients go down) (Manipulate +/- effect
Biomanipulation-prevent algal blooms by adding consumers rather than chemicals
Disturbance• Influences species diversity and
composition• Storms, waves, fires, freezing,
drought, • Moderate disturbance can foster
greater diversity than low or high levels
Ecological succession• Species are replaced by other species• Primary• Secondary• Climax community
Island Biogeography• http://www.youtube.com/watch?v=2R
avt4AqdZI
Island Equilibrium Model
Latitudinal gradients• Species richness increases as
approach tropics• Tropics-older; others have repeatedly
started over (glaciers retreating, etc)• Growing season longer• Sunlight and precipitation higher• Evapotranspiration-evap of water for
soil and plants together
• Zoonotic pathogens: transferred to humans from other animals (vector)
Detritivores• Return nutrients to the soil• Law of conservation of mass
Aquatic Ecosystem• Light limitation• Nutrient limitation• Eutrophication
Biomass-dry mass• *
• *In inverted pyramid, phytoplankton grow, reproduce, and are consumed so quickly by the zooplankton that they never develop a large population size, or standing crop
• Phytoplankton continually replace their biomass at such a rapid rate, they can support a biomass of zooplankton bigger than their own biomass.
The Green World Hypothesis
• Terrestrial herbivores are held in check by a variety of factors.– Mechanical defenses– Chemicals
– Low nutrient concentrations so must consume large quantities
– Abiotic factors-temp & moisture extremes
– Competition
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; oligotrophic-nutrient poor
– On land-temp and water– evotranspiration
Biogeochemical cycles
Nitrogen cycle
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
Population conservation• Focuses on:
– Population size– Genetic diversity– Critical habitat
MVP• Minimum Viable Population• Extinction Vortex
Landscape and regional conservation
• Habitat fragmentation• Movement corridors• Biodiversity hot spot-small area with
an exceptional concentration of endemic species
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
• BIDE birth immigration death emigration
• Additive growth• Multiplicative growth
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