Transfers of energy

• Ecosystem


  Open system where a community interacts with abiotic factors
• Ecosystems without sun

  • Deep sea hydrothermal vents have chemoautotrophic bacteria
  • Caves rely on outside organic matter
• Food chain


  Feeding relationships in an ecosystem
• Food web


  Combination of food chains
• Decomposers


  • Feed on dead or decaying matter
  • Saprotrophs do external digestion (fungi)
  • Detritivores do internal digestion (earthworms)
• Photoautotrophs


  Use light energy to synthesize organic compounds
• Chemoautotrophs


  Oxidation of inorganic compounds to synthesize carbon compounds
• Chemoautotrophs


  • Iron oxidizing bacteria oxidize ferrous ions to ferric ions
  • Use energy released from oxidation to fix carbon dioxide
• Consumers


  Obtain carbon compounds from living organisms
• Digestion

  1. Hydrolysis

  2. Synthesis of carbon compounds involved condensation
• Both autotrophs and heterotrophs release energy from carbon compounds through respiration
• Trophic level


  Position an organism occupies within a feeding sequence
• 90% of energy is lost between each trophic level
• Reasons for energy loss between trophic levels

  • Some organisms are not consumers and die, passed to decomposers
  • Incomplete digestion, indigestible material is egested in feces, energy passes to saprotrophs
  • Cell respiration, carbon compounds oxidized in respiration can't pass to the next trophic level, energy is lost
• Decomposers are not included in food chains
• Energy is lost when decomposers break down dead organisms as heat
• Limit on the number of trophic levels

  Loss of energy stored in biomass at each trophic level limits it
• Biomass


  Dry mass of organisms in an ecosystem
• Productivity

  • Primary production: mass of carbon compounds synthesized from carbon dioxide by autotrophs, grams per meter squared per year
  • Gross primary production: total biomass of carbon compounds made by autotrophs
  • Net primary production: accounts for a loss due to respiration
• Biomes rely on their ability to accumulate biomass depending on photosynthetic rates, it is higher in rainforests than deserts
• Secondary production is lower than primary production
• Net secondary production is less than gross secondary production
• Decreased secondary production at each trophic level
• Carbon sink


  Store of carbon (ocean)
• Carbon flux


  Transfer of carbon (photosynthesis)
• Carbon cycle


  1. Diffusion: carbon dioxide diffuses from the atmosphere or water into autotrophs

  2. Photosynthesis: autotrophs including aquatic plants use carbon dioxide

  3. Decay: dead organic matter is converted into carbon dioxide, it diffuses into the atmosphere or water

  4. Peat formation: acidic an anaerobic conditions, dead organic matter is not fully decomposed

  5. Methane: organic matter in anaerobic conditions is decayed by methane producing bacteria

  6. Combustion of fossil fuels

  7. Shell and bone formation combines bicarbonate with calcium ions, may accumulate as limestone sediments

  8. Lime formation: terrestrial chalk and limestone are quarried and converted to lime which releases carbon dioxide

  9. Volcanic eruptions