Energy Movement

Ecosystem ecology emphasizes energy flow and chemical cycling
  • Ecosystem ecologists view ecosystems as transformers of energy and processors of matter.
  • We can follow the transformation of energy by grouping the species in a community into trophic levels of feeding relationships.

    Ecosystems obey physical laws.

  • The law of conservation of energy states that energy cannot be created or destroyed but only transformed.
    • Plants and other photosynthetic organisms convert solar energy to chemical energy, but the total amount of energy does not change.
    • The total amount of energy stored in organic molecules plus the amounts reflected and dissipated as heat must equal the total solar energy intercepted by the plant.
  • The second law of thermodynamics states that some energy is lost as heat in any conversion process.
    • We can measure the efficiency of ecological energy conversions.
  • Chemical elements are continually recycled.
    • A carbon or nitrogen atom moves from one trophic level to another and eventually to the decomposers and back again.

    Trophic relationships determine the routes of energy flow and chemical cycling in ecosystems.

  • Autotrophs, the primary producers of the ecosystem, ultimately support all other organisms.
    • Most autotrophs are photosynthetic plants, algae or bacteria that use light energy to synthesize sugars and other organic compounds.
    • Chemosynthetic prokaryotes are the primary producers in deep-sea hydrothermal vents.
  • Heterotrophs are at trophic levels above the primary producers and depend on their photosynthetic output.
    • Herbivores that eat primary producers are called primary consumers.
    • Carnivores that eat herbivores are called secondary consumers.
    • Carnivores that eat secondary producers are called tertiary consumers.
  • Another important group of heterotrophs is the detritivores, or decomposers.
    • They get energy from detritus, nonliving organic material such as the remains of dead organisms, feces, fallen leaves, and wood.
    • Detritivores play an important role in material cycling.

    Decomposition connects all trophic levels.

  • The organisms that feed as detritivores form a major link between the primary producers and the consumers in an ecosystem.
  • Detritivores play an important role in making chemical elements available to producers.
    • Detritivores decompose organic material and transfer chemical elements in inorganic forms to abiotic reservoirs such as soil, water, and air.
  • Producers then recycle these elements into organic compounds.
  • An ecosystem’s main decomposers are fungi and prokaryotes