8/25/2015 1 It involves understanding biotic and abiotic factors influencing the distribution and abundance of living things. Biotic Factors • Competitors • Disease • Predators • Food availability • Habitat availability • Symbiotic relationships Abiotic Factors • pH • Temperature • Weather conditions • Water availability • Chemical composition of environment • nitrates, phosphates, ammonia, O 2 , pollution • population growth • competition between species • symbiotic relationships • trophic (=feeding) relationships • origin of biological diversity • interaction with the physical environment Energy Flow & Nutrient Cycle
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8/25/2015
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It involves understanding bioticand abiotic factors influencingthe distribution and abundanceof living things.
Biotic Factors• Competitors
• Disease
• Predators
• Food availability
• Habitat availability
• Symbiotic relationships
Abiotic Factors• pH
• Temperature
• Weather conditions
• Water availability
• Chemical composition ofenvironment
• nitrates, phosphates,ammonia, O2, pollution
• population growth• competition between species• symbiotic relationships• trophic (=feeding) relationships• origin of biological diversity• interaction with the physical environment
Energy Flow & Nutrient Cycle
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Food Chains
• Artificial devices toillustrate energy flowfrom one trophic levelto another
• Trophic Levels:groups of organismsthat obtain theirenergy in a similarmanner
• Total number of levels in a food chaindepends upon locality and number ofspecies
• Highest trophic levels occupied by adultanimals with no predators of their own
• Secondary Production: total amount ofbiomass produced in all higher trophiclevels
Food Chains
Nutrients• Inorganic nutrients incorporated
into cells during photosynthesis- e.g. N, P, C, S
• Cyclic flow in food chains
• Decomposers release inorganicforms that become available toautotrophs again
Energy• Non-cyclic, unidirectional flow• Losses at each transfer from one
trophic level to another- Losses as heat from respiration- Inefficiencies in processing
• Total energy declines from one transferto another- Limits number of trophic levels
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Energy Flow
PrimaryProducer Primary
Consumer SecondaryConsumer
TertiaryConsumer
Food Chain
Decomposer
zooplankton larval fishfish
fungi
Energy Flow through an Ecosystem
heat heatheat
phytoplankton
sun
water
Nutrients
Transfer Efficiencies• Efficiency of energy transfer called
transfer efficiency
• Units are energy or biomass
Et = PtPt-1
Pt = annual production atlevel t
Pt-1 = annual productionat t-1
Transfer Efficiency Example• Net primary production = 150 g C/m2/yr• Herbivorous copepod production = 25 g C/m2/yr
• Typical transfer efficiency ranges*Level 1-2 ~20%*Levels 2-3, …: ~10%