Can someone explain positive and negative feedback with examples?

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Srslyno
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I just can't get the hang of making sense around it and also applying it in questions, how would you bring it in?
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jsg9
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Positive feedback amplifies a change away from the constant or normal range. For this reason it’s not involved in homeostasis. For example, in labour, the head of the baby will push against the cervix. A nerve impulse to the brain will detect this and cause the hormone oxytocin to be secreted from the pituitary gland. Oxytocin will travel in the blood and then cause more uterine contractions, which cause the baby’s head to push more against the cervix, and so the process will start again. This is amplifying the change, i.e. increasing the number of uterine contractions.

Negative feedback will minimise a change back towards the constant or normal range. For example, when your body temperature rises above the normal temperature. The thermoregulatory centre of the hypothalamus will detect the increased body temperature causing effectors to respond to the change. Pre-capillary sphincter muscle will relax causing vasodilation - more heat loss from skin surface to surroundings. Sweat production will be increased so that more evaporates from the skin which decreases body temp. The body temperature will be returned to within normal range.

So basically, negative feedback will minimise changes and so is involved in homeostasis and positive feedback amplifies a change away from the normal.
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Srslyno
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(Original post by jsg9)
Positive feedback amplifies a change away from the constant or normal range. For this reason it’s not involved in homeostasis. For example, in labour, the head of the baby will push against the cervix. A nerve impulse to the brain will detect this and cause the hormone oxytocin to be secreted from the pituitary gland. Oxytocin will travel in the blood and then cause more uterine contractions, which cause the baby’s head to push more against the cervix, and so the process will start again. This is amplifying the change, i.e. increasing the number of uterine contractions.

Negative feedback will minimise a change back towards the constant or normal range. For example, when your body temperature rises above the normal temperature. The thermoregulatory centre of the hypothalamus will detect the increased body temperature causing effectors to respond to the change. Pre-capillary sphincter muscle will relax causing vasodilation - more heat loss from skin surface to surroundings. Sweat production will be increased so that more evaporates from the skin which decreases body temp. The body temperature will be returned to within normal range.

So basically, negative feedback will minimise changes and so is involved in homeostasis and positive feedback amplifies a change away from the normal.
hey thank you for the biology! this was meant for the geography forum. I'm still quite new to this so I'm not sure if I've posted this in the right forum.
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username1292215
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(Original post by Srslyno)
hey thank you for the biology! this was meant for the geography forum. I'm still quite new to this so I'm not sure if I've posted this in the right forum.
What they have said is the same as geography. For example with coasts.

Positive feedback is when waves move with even more destructive energy

For climate change:

Positive feedback increases the rate of global warming, while negative feedback will reduce the rate
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username2088165
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(Original post by Srslyno)
I just can't get the hang of making sense around it and also applying it in questions, how would you bring it in?
As the other posters have said, positive feedbacks amplify an initial change, whereas negative feedbacks reverse the initial change.

A positive feedback example: increased global temperatures cause melting of glaciers and ice sheets, which means less incoming solar radiation is reflected back into space (i.e. the Earth's albedo is lowered). More solar radiation is therefore absorbed by the Earth and re-emitted as infrared radiation, which becomes trapped in the atmosphere and further increases global temperatures.

A negative feedback example: an increase in temperature causes an increase in rates of photosynthesis. As a result, higher volumes of carbon dioxide are taken up by plants and stored in biomass, and the reduction in atmospheric carbon dioxide may therefore reverse the effect of the initial warming.

I hope that makes sense
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Srslyno
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(Original post by Leviathan1741)
As the other posters have said, positive feedbacks amplify an initial change, whereas negative feedbacks reverse the initial change.

A positive feedback example: increased global temperatures cause melting of glaciers and ice sheets, which means less incoming solar radiation is reflected back into space (i.e. the Earth's albedo is lowered). More solar radiation is therefore absorbed by the Earth and re-emitted as infrared radiation, which becomes trapped in the atmosphere and further increases global temperatures.

A negative feedback example: an increase in temperature causes an increase in rates of photosynthesis. As a result, higher volumes of carbon dioxide are taken up by plants and stored in biomass, and the reduction in atmospheric carbon dioxide may therefore reverse the effect of the initial warming.

I hope that makes sense
thank you!!
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Skkkk
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(Original post by Srslyno)
thank you!!
Do U do well in English I need someone marking my essay
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Srslyno
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(Original post by Skkkk)
Do U do well in English I need someone marking my essay
sorry, I don't take A level English.
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morc13
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A change that promotes itself = a positive feedback
Loop E.g. Global warming causes more water to evaporate, water vapour then acts as a greenhouse gas and increases global warming (which will cause more water to evaporate...)

A change that reduces the cause of the change = negative feedback loop. E.G. If the product of a chemical reaction is able to inhibit the same reaction that produced it.
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Kappo99
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Negative feedback is a response to a change that restores equilibrium. For example:
- in the water cycle, exceptionally heavy rain will increase the water table (due to the recharge of aquifers) after a period of drought to normal levels.
- in the carbon cycle, an increase in carbon dioxide in the atmosphere will stimulate photosynthesis and thus the biosphere will hold more carbon reducing atmospheric CO2 levels back to what they were.

Positive feedback is a response to a change that generates further change. For example:
- Global warning will intensify the carbon cycle, speed up decomposition and release more CO2 to the atmosphere, amplifying the greenhouse effect.
- Where global warming is occurring in the Arctic tundra, sea ice and snow cover is shrinking leaving more land exposed. More insulation is absorbed which warms the tundra and melts the permafrost. Permafrost is a vast carbon sink, so melting will expose organic material to decomposition and oxidation and increase atmospheric carbon dioxide levels contributing to further global warming.

Took me ages to learn this, but I hope it helps 😄
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