Economics 1021A/B Lecture Notes - Lecture 20: Steller Sea Lion, Autotroph, Omnivore

• School: Western University
• Department: Economics
• Course: Economics 1021A/B
• Professor: Tim Hain

Document Summary

The fraction is greater in aquatic ecosystems than terrestrial: most is associated with detritivores, primarily bacterial and fungi. In terrestrial ecosystems, energy and biomass pyramids are similar because biomass is closely associated with energy production. In aquatic ecosystems, the biomass pyramid may be inverted: the primary producers are phytoplankton with short life spans and high turnover. This suggests that herbivore production is limited by the amount of food available. Trophic efficiency: amount of energy at one trophic level divided by the amount of energy at the trophic level immediately below it. Changes in the abundance of organisms at one trophic level can influence energy flow at multiple trophic levels. In reality, both controls are operating simultaneously in ecosystems: top-down control has implications for the effects of trophic interactions on energy flow. 2008: disturbance frequency did not impact trophic levels, but the top predator species changed. Food webs: conceptual models of the trophic interactions of organisms in an ecosystem.