From studying ecosystems and biomes, it may seem as if there is complete "bottom up" control, that the producers determine the life and success of the ecosystem. Yet closer examination shows "top down" control by the third trophic level is essential as
well. Evaluate why this is so, citing at least one good example.
What will be an ideal response?
Producers certainly serve as the foundation of an ecosystem, providing the net primary production that supports the rest of the ecosystem. However, the upper trophic levels provide population controls on the other consumers, which provides the necessary balance and prevents depletion of resources. The intentional flooding of an area in Venezuela that produced many small islands, some with insufficient size or biomass to support secondary consumers is a good example. Without secondary consumers, herbivores depleted resources and essentially destroyed the ecosystem. Somewhat larger islands with enough biomass to support the third trophic level maintained a more balanced ecosystem.
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Fill in the blank(s) with the appropriate word(s).