Feedback

For other uses, including Audio feedback, see Feedback (disambiguation)

Feedback in nature

In biological systems such as organisms, ecosystems, or the biosphere, most parameters must stay under control within a narrow range around a certain optimal level under certain environmental conditions. The deviation of the optimal value of the controlled parameter can result from the changes in internal and external environments. A change of some of the environmental conditions may also require change of that range to change for the system to function. The value of the parameter to maintain is recorded by a reception system and conveyed to a regulation module via an information channel.

Related Topics:
Biological - Organism - Ecosystem - Biosphere

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Biological systems contain many types of regulatory circuits, among which positive and negative feedbacks. Positive and negative don't imply consequences of the feedback have positive or negative final effect. The negative feedback loop tends to slow down a process, while the positive feedback loop tends to accelerate it.

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Feedback and regulation are self related. The negative feedback helps to maintain stability in a system in spite of external changes. It is related to homeostasis. Positive feedback amplifies possibilities of divergences (evolution, change of goals); it is the condition to change, evolution, growth; it gives the system the ability to access new points of equilibrium.

Related Topics:
Homeostasis - Equilibrium

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For example, in an organism, most positive feedbacks provide for fast autoexcitation of elements of endocrine and nervous systems (in particular, in stress responses conditions) and play a key role in regulation of morphogenesis, growth, and development of organs, all processes which are in essence a rapid escape from the initial state.

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Homeostasis is especially visible in the nervous and endocrine systems when considered at organism level.

Related Topics:
Nervous - Endocrine systems

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Feedback is also central to the operations of genes and gene regulatory networks. repressor (see Lac repressor) and activator proteins are used to create genetic operons, which were identified by Francois Jacob and Jacques Monod in 1961 as feedback loops.

Related Topics:
Gene - Gene regulatory network - Repressor - Lac repressor - Activator - Protein - Operons - Francois Jacob - Jacques Monod - 1961

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Any self-regulating natural process involves feedback and is prone to hunting. A well known example in ecology, is the oscillation of the population of snowshoe hares due to predation from lynxes.

Related Topics:
Ecology - Snowshoe hare - Lynx

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In zymology, feedback serves as regulation of activity of an enzyme by its direct product(s) or downstream metabolite(s) in the metabolic pathway.

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There is an ice-albedo positive feedback loop whereby melting snow exposes more dark ground (of lower albedo), which in turn absorbs heat and causes more snow to melt. This is part of the evidence of the danger of global warming.

Related Topics:
Albedo - Global warming

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Compare with: feed-forward

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