Autotrophs (producers) synthesize their own energy, creating organic materials that are utilized as fuel by heterotrophs (consumers).
Productivity, measured by gross and net primary productivity, is defined as the amount of energy that is incorporated into a biomass.
Energy is lost as it is transferred between trophic levels; the efficiency of this energy transfer is measured by NPE and TLTE.
Ecological pyramids, which can be inverted or upright, depict biomass, energy, and the number of organisms in each trophic level.
When toxic substances are introduced into the environment, organisms at the highest trophic levels suffer the most damage.