Ecology
In ecology, top-down control refers to when a top predator controls the structure or population dynamics of the ecosystem. The classic example is of kelp forest ecosystems. In such ecosystems, sea otters are a keystone predator. They prey on urchins which in turn eat kelp. When otters are removed, urchin populations grow and reduce the kelp forest creating urchin barrens. In other words, such ecosystems are not controlled by productivity of the kelp but rather a top predator.
Bottom up control in ecosystems refers to ecosystems in which the nutrient supply and productivity and type of primary producers (plants and phytoplankton) control the ecosystem structure. An example would be how plankton populations are controlled by the availability of nutrients. Plankton populations tend to be higher and more complex in areas where upwelling brings nutrients to the surface.
There are many different examples of these concepts. It is not uncommon for populations to be influenced by both types of control.
Read more about this topic: Top-down And Bottom-up Design
Famous quotes containing the word ecology:
“... the fundamental principles of ecology govern our lives wherever we live, and ... we must wake up to this fact or be lost.”
—Karin Sheldon (b. c. 1945)