Ecology Notes

1
Ecology Notes

• Chapter 54-56 Ecosystems, Populations and
  Communities

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Ecology

• Components abioticnonliving chemical
  physical factors bioticliving factors
• Populationgroup of individuals of the same
  species in a particular geographical area
• Communityassemblage of populations of different
  species
• Ecosystemall abiotic factors and the community
  of species in an area
• Rachel Carson, 1962, Silent Spring

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Population characteristics

• Density of individuals per unit of area
• Dispersion pattern of spacing
• random unpredictable, patternless spacing (c)
  clumped patchy aggregation
  (a) uniform even spacing (b)

4
Demography factors that affect growth decline
of populations

• Birthrate (natality, fecundity) of offspring
  produced
• Death rate (mortality)
• Age structure relative number of individuals of
  each age
• Survivorship curve plot of numbers still alive
  at each age

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Population Growth Models

• Exponential model (blue)  idealized population
  in an unlimited environment (J-curve) r-selected
  species (rper capita growth rate)
• Logistic model (red) carrying capacity (K)
  maximum population size that a particular
  environment can support (S-curve) K-selected
  species

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Population life history strategies

• r-selected (opportunistic)
• Short maturation lifespan
• Many (small) offspring usually 1 (early)
  reproduction no parental care
• High death rate

• K-selected (equilibrial)
• Long maturation lifespan
• Few (large) offspring usually several (late)
  reproductions extensive parental care
• Low death rate

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Population limiting factors

• Density-dependent factors competition
• predation
• stress/crowding
• Waste accumulation
• Density-independent factors weather/climate
• periodic disturbances

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Abiotic factors

• Biospherethe sum of all the planets ecosystems
• Biome areas of predominant flora and fauna
• Temperature
• Water
• Sunlight
• Wind
• Rocks Soil
• Periodic disturbances

Ecotone biome grading areas
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Global climate

• Seasons

Precipitation Winds
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Lake stratification turnover

• Thermal stratification vertical temperature
  layering
• Biannual mixing spring and summer
• Turnover changing water temperature profiles
  brings oxygenated water from the surface to the
  bottom and nutrient rich water form the bottom to
  the surface

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Aquatic biomes

• Vertical stratification photic zone
  photosynthetic light aphotic zone little light
  thermocline narrow stratum of rapid temperature
  chang benthic zone bottom substrate
• Benthos community of organisms
• Detritus dead organic matter food for benthic
  organisms

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Freshwater biomes

• Littoral zone shallow, well-lit waters close to
  shore
• Limnetic zone well-lit, open water farther from
  shore
• Profundal zone deep, aphotic waters
• Lake classification oligotrophic deep,
  nutrient poor eutrophic shallow, high nutrient
  content
• mesotrophic moderate productivity
• Wetland area covered with water
• Estuary area where freshwater merges with ocean

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Marine biomes

• Intertidal zone area where land meets water
• Neritic zone shallow regions over continental
  shelves
• Oceanic zone very deep water past the
  continental shelves
• Pelagic zone open water of any depth
• Benthic zone seafloor bottom
• Abyssal zone benthic region in deep oceans

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Terrestrial biomes

• Tropical forests equator most complex constant
  temperature and rainfall canopy
• Savanna tropical grassland with scattered trees
  occasional fire and drought large herbivores
• Desert sparse rainfall (lt30cm/yr)
• Chaparral spiny evergreens at midlatitudes along
  coasts
• Temperate grassland all grasses seasonal
  drought, occasional fires large mammals
• Temperate deciduous forest midlatitude regions
  broad-leaf deciduous trees
• Coniferous forest cone-bearing trees
• Tundra permafrost very little precipitation

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Relationships, I

• Trophic structure / levels feeding relationships
  in an ecosystem
• Primary producers the trophic level that
  supports all others autotrophs
• Primary consumers herbivores
• Secondary and tertiary consumers carnivores
• Detrivores/detritus special consumers that
  derive nutrition from non-living organic matter
• Food chain trophic level food pathway

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Relationships, II

• Food webs interconnected feeding relationship in
  an ecosystem

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Energy Flow, I

• Primary productivity (amount of light energy
  converted to chemical energy by
  autotrophs) Gross (GPP) total energy
  
  Net (NPP) represents
  the storage of energy available to consumers
  Rs respiration
• NPP GPP - Rs
• Biomass primary productivity reflected as dry
  weight of organic material
• Secondary productivity the rate at which an
  ecosystem's consumers convert chemical energy of
  the food they eat into their own new biomass

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Energy Flow, II

• Ecological efficiency of E transferred from
  one trophic level to the next (5-20)
• Pyramid of productivity multiplicative loss of
  energy in trophic levels
• Biomass pyramid trophic representation of
  biomass in ecosystems
• Pyramid of numbers trophic representation of the
  number of organisms in an ecosystem

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Chemical Cycling

• Biogeochemical cycles the various nutrient
  circuits, which involve both abiotic and biotic
  components of an ecosystem
• Water
• Carbon
• Nitrogen
• Phosphorus

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Community structure

• Community an assemblage of populations living
  close enough together for potential interaction
• Richness (number of species) abundance.
• Species diversity
• Hypotheses Individualistic chance assemblage
  with similar abiotic requirements
• Interactive assemblage locked into association
  by mandatory biotic interactions

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Interactions

• Interspecific (interactions between populations
  of different species within a community)
  Predation including parasitism may
  involve a keystone species/predator Competition
• Commensalism
• Mutualism

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Predation defense

• Cryptic (camouflage) coloration
• Aposematic (warning) coloration
• Mimicry superficial resemblance to another
  species v Batesian palatable/
  harmless species mimics an unpalatable/ harmful
  model v Mullerian 2 or more
  unpalatable, aposematically colored species
  resemble each other

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Competition a closer look

• Interference actual fighting over resources
• Exploitative consumption or use of similar
  resources
• Competitive Exclusion Principle (Lotka /
  Volterra) 2 species with similar needs for the
  same limiting resources cannot coexist in the
  same place vGause experiment predators and prey
  limit each other

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Competition evidence

• Resource partitioning sympatric species consume
  slightly different foods or use other resources
  in slightly different ways

• Character displacement sympatric species tend to
  diverge in those characteristics that overlap

Ex Anolis lizard sp. perching sites in the
Dominican Republic
Ex Darwins finch beak size on the Galapagos
Islands
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The Niche

• Ecological niche the sum total of an organisms
  use of biotic and abiotic resources in its
  environment its ecological role
  v fundamental the set of resources a
  population is theoretically capable of using
  under ideal conditions v realized the resources
  a population actually uses
• Thus, 2 species cannot coexist in a community if
  their niches are identical

Ex Barnacle sp. on the coast of Scotland
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Succession

• Ecological succession transition in species
  composition over ecological time
• Primary begun in lifeless area no soil, perhaps
  volcanic activity or retreating glacier
• Secondary an existing community has been cleared
  by some disturbance that leaves the soil intact

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Biodiversity crisis

• Extinction natural phenomenon, however, rate is
  of concern..
• 50 loss of species when 90 of habitat is lost
• Major Threats
• Habitat destruction single greatest threat
  cause of 73 of species designation as extinct,
  endangered, vulnerable, rare 93 of coral reefs
• Competition by exotic (non-native) species
  cause of 68 of species designation as extinct,
  endangered, vulnerable, rare travel
• Overexploitation commercial harvest or sport
  fishing illegal trade

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Biodiversity Human welfare

• 25 of all medical prescriptions
• Genetic variability
• Aesthetic and ethical reasons
• Species survival

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Conservation biology focus

• Preservationism setting side select areas as
  natural and underdeveloped
• Resource conservation public lands to meet the
  needs of agriculture and extractive industries,
  i.e., multiple use
• Evolutionary / ecological view natural systems
  result from millions of years of evolution and
  ecosystem processes are necessary to maintain the
  biosphere

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Geographic distribution of biodiversity

• Energy availability solar radiation
• Habitat heterogeneity environmental patchiness
• Niche specialization narrow resource range
  specialization
• Population interactions complex population
  interactions

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Population species level conservation

• Biodiversity hot spot small area with an
  exceptional concentration of species
• Endemic species species found nowhere else
• Endangered species organism in danger of
  extinction
• Threatened species likely to become endangered
  in the foreseeable future
• Bioremediation use of living organisms to
  detoxify polluted systems

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Human Impact

• Biological magnification trophic process in
  which retained substances become more
  concentrated at higher levels
• Greenhouse effect warming of planet due to
  atmospheric accumulation of carbon dioxide
• Ozone depletion effect of chlorofluorocarbons
  (CFCs) released into the atmosphere
• Rainforest destruction
• Cause Overpopulation?