Summarizing Energy Flow Through Ecosystems

Summary

Organisms in an ecosystem acquire energy in a variety of ways, which is transferred between trophic levels as the energy flows from the bottom to the top of the food web, with energy being lost at each transfer. The efficiency of these transfers is important for understanding the different behaviors and eating habits of warm-blooded versus cold-blooded animals. Modeling of ecosystem energy is best done with ecological pyramids of energy, although other ecological pyramids provide other vital information about ecosystem structure.

Glossary

assimilation

biomass consumed and assimilated from the previous trophic level after accounting for the energy lost due to incomplete ingestion of food, energy used for respiration, and energy lost as waste

biomagnification

increasing concentrations of persistent, toxic substances in organisms at each trophic level, from the primary producers to the apex consumers

biomass

total weight, at the time of measurement, of living or previously living organisms in a unit area within a trophic level

chemoautotroph

organism capable of synthesizing its own food using energy from inorganic molecules

ecological pyramid

(also, Eltonian pyramid) graphical representation of different trophic levels in an ecosystem based of organism numbers, biomass, or energy content

gross primary productivity

rate at which photosynthetic primary producers incorporate energy from the sun

net consumer productivity

energy content available to the organisms of the next trophic level

net primary productivity

energy that remains in the primary producers after accounting for the organisms’ respiration and heat loss

net production efficiency (NPE)

measure of the ability of a trophic level to convert the energy it receives from the previous trophic level into biomass

trophic level transfer efficiency (TLTE)

energy transfer efficiency between two successive trophic levels