Energy Flow in an Ecosystem

Energy flows one way through an ecosystem.

  1. Trophic level are levels of consumption:
    • 1st trophic level = primary producers.
    • 2nd trophic level = primary consumers.
    • 3rd trophic level = secondary consumers.
    • 4th trophic level = tertiary consumers.
    • 5th trophic level = detritivores.
    Not all trophic levels may be present.
  2. Biomass - total weight of all living organisms in an ecosystem.
  3. Biomagnification - tendency of toxins to accumulate in higher trophic levels.
  4. Food chain - simple, linear series of producers and consumers.
  5. Food web - complex diagram with branching lines showing the trophic relationships of organisms in an ecosystem.

Autotrophs - the producers

(self-nourishing)
  1. photosynthesis - plants, approx 1% efficiency.
  2. chemosynthesis - deep-sea vent H2S bacteria.

Heterotrophs - the consumers

(nourishment from others)
  1. herbivores - feed on plants, converting about 10% of the consumed energy into biomass.
  2. carnivore - consume other animals (includes parasites), also about 10% conversion efficiency.
  3. detritivore - consume refuse of ecosystem (includes decomposers, saprophyte and scavengers).
  4. omnivore - feeds at many trophic levels.
  5. filter feeders - filter food from liquid medium.

An Organism's Production Efficiency

  1. Production efficiency = growth + reproduction
  2. Energy intake = growth + reproduction - maintenance
  3. Efficiencies vary depending on :
    • the organism must maintain a constant body temperature
    • if it consumes difficult to digest plant material