Feedback Mechanisms. Positive and Negative Feedback loops  A negative feedback loop is one that tends to slow down a process, whereas the positive feedback.

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Presentation transcript:

Feedback Mechanisms

Positive and Negative Feedback loops  A negative feedback loop is one that tends to slow down a process, whereas the positive feedback loop tends to accelerate it.

Negative Feedback loops  Example: Predator- Prey relationships  as prey population growth goes up, the predator population eats well and their populations increase, but then there are many predators and prey goes down (so a "+" arrow followed by a "-" arrow).  Another example:  if a plant becomes too dense, individuals start to compete with each other for limiting water and then they thin out (density dependence). Once they are thinned out there is increased water availability for the survivors. Plant cover can’t keep increasing (or decrease too much either) so the negative feedbacks stabilize plant cover.

Positive Feedback Loop  A positive feedback is when there are two plusses between the two processes, such as when water availability supports the growth of a plant species (+) and more plants increase soil water (through increased infiltration and decreased evaporation) available to support plant growth (+). You could also have two minuses (-)