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Homeostasis

Homeostasis. Walter Cannon 1932 “The Wisdom of the Body” Jame Lovelock ~1969 Gaia hypothesis (Lovelock, J.E.; Margulis, L. (1974). "Atmospheric homeostasis by and for the biosphere- The Gaia hypothesis". Tellus 26 (1): 2–10.

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Homeostasis

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  1. Homeostasis • Walter Cannon 1932 “The Wisdom of the Body” • Jame Lovelock ~1969 Gaia hypothesis (Lovelock, J.E.; Margulis, L. (1974). "Atmospheric homeostasis by and for the biosphere- The Gaia hypothesis". Tellus26 (1): 2–10.

  2. Draw a causal lop diagram describing a self regulating component of the human body.

  3. Example • Draw a causal loop diagram to describe the following: • The sun becomes brighter causing Earth to warm to a new equilibrium temperature. sunlight Earth’s mean Temperature + - - + Emitted infrared energy

  4. Coffee System The hotter the coffee is The faster it cools Cooling Rate Tc-TR + Tc The higher the cooling rate The colder the coffee TR Cooling Rate Tc-TR -

  5. Coffee System The hotter the coffee is The faster it cools The higher the cooling rate The colder the coffee - Cooling Rate Tc-TR Tc + - = - TR

  6. Negative connection The higher the cooling rate The colder the coffee Cooling Rate Tc-TR Tc - TR

  7. Positive connection The hotter the coffee is The faster it cools Tc Cooling Rate Tc-TR + TR

  8. Negative feedback loop The hotter the coffee is The faster it cools The higher the cooling rate The colder the coffee - Cooling Rate Tc-TR Tc + - = - TR

  9. Cools with a characteristic time constant, t~10 minutes

  10. Homeostasis is internal balance

  11. Equilibrium

  12. Stable equilibrium (negative feedback)

  13. Unstable equilibrium (positive feedback) • ,

  14. Perturbations Small changes that disturb a system from its equilibrium state. Hot Plate Hot Plate

  15. A simple Earth TE Heating rate

  16. A simple Earth Albedo Absorbed solar TE Heating rate Complete the system diagram

  17. Daisy World simulation

  18. Daisy World Average surface Temp Daisy coverage Ts Albedo Daisies Daisies Ts

  19. Daisy World Daisies Ts Ts Daisies Daisy coverage Average surface Temp

  20. Daisy World Ts Daisies P1 Daisy coverage P2 Average surface Temp Daisies Daisies Ts Ts P1 P2 albedo albedo

  21. Daisy World Model

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