1. 1.1.5. Equilibria

3. Equilibrium Equilibrium describes the average condition of a system, as measured through one of its elements or attributes, over a specific period of time.

4. Steady state equilibrium Steady state equilibrium is an average condition of a system where the trajectory remains unchanged in time.Steady state equilibrium Figure : Example of the state of a steady state equilibrium over time.

5. dynamic equilibrium A dynamic equilibrium occurs when there are unrepeated average states through time.dynamic equilibrium Figure : Example of the state of a dynamic equilibrium over time.

6. Static equilibrium Static equilibrium occurs where force and reaction are balanced and the properties of the system remain unchanged over time.Static equilibrium Figure : Example of the state of a static equilibrium over time.

7. stable equilibrium In a stable equilibrium the system displays tendencies to return to the same equilibrium after disturbance.stable equilibrium disturbance Figure : Example of the state of a stable equilibrium over time.

8. unstable equilibrium In an unstable equilibrium the system returns to a new equilibrium after disturbance.unstable equilibrium disturbance Figure : Example of the state of an unstable equilibrium over time.

9. 1.1.6 Positive and Negative Feedback

11. The way that living systems and even inanimate systems self- regulate or maintain homeostasis (the maintenance of a steady state in an organism, ecosystem or biosphere) is through feedback systems

12. Feedback loop *a system ’ s output serves as input to that same system *A circular process

13. feedback process, in diagrammatic form, consists of a set of labeled system components and connecting arrows that form one or more closed loops (see Figure 1). Each arrow is accompanied by a C, −, or 0, assigned according to the nature of the causal connection between components, as shown in Figure 1.

14. POSITIVE FEEDBACK high temperatures increase evaporation leading to more water vapour in the atmosphere. Water vapour is a greenhouse gas which traps more heat worsening Global Warming. Atmosphere Oceans Water Vapour + + + + Global Warming HeatEnergy 14 Sun Evaporation

15. Positive Feedback Loop A feedback loop in which the output of one type acts as an input that moves the system in the same direction. The input and output drive the system further toward one extreme or another

16. Positive feedbackPositive feedback amplifies or increases change; it leads to exponential deviation away from an equilibrium. changes are reinforced. This takes ecosystems to new positions Examples: exponential growth in human population, spread of cancer, erosion Rare in nature –But are common in natural systems altered by human impact

17. NEGATIVE FEEDBACK Population of Hare Population of Lynx + - In this example, when the Hare population increases, the Lynx population increases too in response to the increase in food offer which illustrates both Bottom-Up regulation and Positive Feedback. However, when the Lynx population increases too much, the large number of lynxes will pray more hares reducing the number of hares. As hares become fewer, some lynxes will die of starvation regulating the number of lynx in the population. This illustrates both Top-Down and negative Feedback regulation.

18. Negative Feedback Loop- A feedback loop in which the output of one type acts as an input that moves the system in the opposite direction. The input and output essentially neutralizes each other’s effects, stabilizing the system.

19. Eg:Negative feedback loop Input and output essentially neutralize one another –Stabilizes the system –Example: body temperature –Most systems in nature

20. Negative feedback: an example of population control