Buffers and Feedback Loops
Cla
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Buffers and Feedback Loops
Buffersare agents or
regulatorymechanisms
that reduce or minimize
fluctuations and change
A forest experiences less fluctuation
in temperature, wind, and humidity than an
unforested area
Example
Buffers and Feedback Loops
Because the trees cool with their shade, block winds, and their fallen
leaves help keep the soil moist
Thus the microclimate in the forest is buffered against extremes
Less fluctuation….. Less change……
How Feedback Loops Function – Example One
A feedback is a signal that can be detectedand can trigger a response
Imaginean air-conditioner
regulatedby a
thermostattime
1
How Feedback Loops Function
As the room warms, the thermostat
detectsthe change,
and causes theair-conditioner to
switch ontime
2
and in response, the temperature begins to fall
time
3 As temperaturescool, the thermostat
again detectsthe change
and shuts off theair-conditioner
and, in response, the room begins to warm again
How Feedback Loops Function
time
4These repeated reversals
illustrate the usefulness of
negative feedbacks
Negative feedback loops help bring constancy to a systemand help buffer the system against
Extremes Fluctuations, and Change
* Remember, negative does not mean ”bad” and positive does not mean “good”
Negative feedback loops help bring constancy to a system
time
Extremes Fluctuations and Change
Reducing
They help produce and maintain an active stateof constancy known as.
time
Homeostasis
:the tendency of a system, esp. the physiological system of higher animals, to maintain internal stability.
Some Feedback Loops Can Destabilize
What is the oppositeof a negative feedback loop?
Answer:
A positive feedback loop
When a signal is detected in a
positive feedback system
The system responds by
Amplifying Intensifying Magnifying or Accelerating
the original trend
We all know, snow reflects sun back into space
-if the planet gets a little warmer, snow melts
-with less snow, more sunlight is absorbed by planet
-the increased absorption accelerates warming
-etc., etc., etc.
Positive Feedback Loop
Living systemstend to benefit
because the interactions of many species help maintain
from
Negative Feedback Loops
Stability Constancy and Homeostasis in the system
Buffers and Feedbacks on a Planetary Scale
Buffers and Feedbacks on a Planetary Scale
NASA consultant James Lovelock helps us see
buffers and negativefeedback systems at work on a
planetary scale
First, envision an imaginary planet that is perfectly
round, smooth, grey and lifeless
He calls his imaginary planet
"Daisyworld"
If Daisyworld'ssun heats up and
emits more radiation, what will happen to Daisyworld's
temperature?
The planetary temperature will increase
Decreased Solar Output
What will happen toDaisyworld's temperature if its star becomes cooler and emits
less radiation?
The planetary temperature will go down
Next imagine thatDaisyworld is inhabited by two species of organisms
White daisies that reflect light energy
And dark daisies that absorb light energy
Imagine that 100% of Daisyworld's surface is coveredwith equal numbers of these two species
What happensif Daisyworld's
sun becomescooler?
Will both daisy species be affected in the same way?
Decreased Solar Output
As a result, dark daisies increase in numbers
because theyabsorb
the energy that arrives
The dark daisies are better able to survivea decrease in solar radiation
Decreased Solar Output
In contrast, thelight daisies reflect the
light that arrivesand their
numbers decline
Decreased Solar Output
Daisyworld remains warmer than it would be if it were entirely lifeless
With so many additional dark daisies absorbing solar radiation,
Increased Solar Output
This time the dark daisies absorb too much of the
extra solar output
What if Daisyworld's star heats up?
and their numbers decline
and cover a greater portionof Daisyworld's surface
The light daisies, however,
reflectmuch of the excess heat so
that they survive
Significance
The presence of life
helps moderate planetary conditions
helps reduce fluctuations and change
buffers Daisyworld’s temperature
( in this case, two mindless species of daisies)
Positive and Negative feedback loops in Global Warming
Both negative and positive feedback processes occur in the atmosphere. If negative feedback loops are strong, then global
warming will be more moderate. If positive feedback loops prevail, global warming could be catastrophic for life as we
know it.
1. Increased algae populations reduce [CO2] in atmosphere and causes cooling.
2. Increased plant growth will reduce [CO2] in atmosphere and causes cooling.
3. Increased water evaporation will increase cloud cover and cause cooling.
The Negative Feedback loop
The Positive Feedback Loop
4. Increased evaporation adds more water vapor to atmosphere causing warming
5. Melting of permafrost releases more methane gas causing warming
6. Reduced summer snow-pack decreases Earth’s albedo causing warming
7. Increased use of air conditioning using more fossil fuels causes warming