1. Buffers and Feedback Loops Class Notes 1:6

2. Buffers and Feedback Loops Buffers are agents or regulatory mechanisms that reduce or minimize fluctuations and change

3. A forest experiences less fluctuation in temperature, wind, and humidity than an unforested area Example Buffers and Feedback Loops

4. 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……

5. How Feedback Loops Function – Example One A feedback is a signal that can be detected and can trigger a response Imagine an air-conditioner regulated by a thermostat time 1

6. How Feedback Loops Function As the room warms, the thermostat detects the change, and causes the air-conditioner to switch on time 2 and in response, the temperature begins to fall

7. time 3 As temperatures cool, the thermostat again detects the change and shuts off the air-conditioner and, in response, the room begins to warm again How Feedback Loops Function

8. time 4 These repeated reversals illustrate the usefulness of negative feedbacks Negative feedback loops help bring constancy to a system and help buffer the system against Extremes Fluctuations, and Change * Remember, negative does not mean ”bad” and positive does not mean “good”

9. Negative feedback loops help bring constancy to a system time  Extremes  Fluctuations and  Change Reducing

10. They help produce and maintain an active state of constancy known as. time Homeostasis :the tendency of a system, esp. the physiological system of higher animals, to maintain internal stability.

11. Some Feedback Loops Can Destabilize

12. What is the opposite of a negative feedback loop? Answer: A positive feedback loop

13. When a signal is detected in a positive feedback system The system responds by  Amplifying  Intensifying  Magnifying or  Accelerating the original trend

14. 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

15. Living systems tend to benefit because the interactions of many species help maintain from Negative Feedback Loops  Stability  Constancy and  Homeostasis in the system

16. Buffers and Feedbacks on a Planetary Scale

17. NASA consultant James Lovelock helps us see buffers and negative feedback systems at work on a planetary scale

18. First, envision an imaginary planet that is perfectly round, smooth, grey and lifeless He calls his imaginary planet " Daisyworld "

19. If Daisyworld's sun heats up and emits more radiation, what will happen to Daisyworld's temperature? The planetary temperature will increase

20. Decreased Solar Output What will happen to Daisyworld's temperature if its star becomes cooler and emits less radiation? The planetary temperature will go down

21. Next imagine that Daisyworld is inhabited by two species of organisms White daisies that reflect light energy

22. And dark daisies that absorb light energy

23. Imagine that 100% of Daisyworld's surface is covered with equal numbers of these two species

24. What happens if Daisyworld's sun becomes cooler? Will both daisy species be affected in the same way? Decreased Solar Output

25. As a result, dark daisies increase in numbers because they absorb the energy that arrives The dark daisies are better able to survive a decrease in solar radiation Decreased Solar Output

26. In contrast, the light daisies reflect the light that arrives and their numbers decline Decreased Solar Output

27. Daisyworld remains warmer than it would be if it were entirely lifeless With so many additional dark daisies absorbing solar radiation,

28. 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

29. and cover a greater portion of Daisyworld's surface The light daisies, however, reflect much of the excess heat so that they survive

30. 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)

31. 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.

32. 1. Increased algae populations reduce [CO 2 ] in atmosphere and causes cooling. 2. Increased plant growth will reduce [CO 2 ] in atmosphere and causes cooling. 3. Increased water evaporation will increase cloud cover and cause cooling. The Negative Feedback loop

33. 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