Understanding Systems and their Characteristics

1. Quiz • Outline the concept and characteristics of systems. • Give some examples of systems from the following subject areas: • Biology • Environmental sciences • Every Day Life • What does it mean that systems can be applies on a range of scales. Give some examples to help make your point. • Construct a table to compare the exchange of matter and energy in open, closed, and isolated systems. Give an example of each.

2. Assessment Statements 1.1.4 Describe how the first and second law of thermodynamics are relevant to environmental systems. 1.1.5 Explain the nature of equilibria 1.1.6 Define and explain the principles of positive feedback and negative feedback.

3. Ecosystems involve interrelationships among climate, geology, soil, vegetation, and animals. These components are linked together transfers of energy and or matter.

4. Two basic processes occur in an ecosystem: 1. The cycling of matter 2. A flow of energy

5. The cycling of matter. Because there are only finite amounts of nutrients available on the earth, they must be recycled in order to ensure the continued existence of living organisms. Examples are the:

6. Runoff Runoff Surface runoff (rapid) Surface runoff (rapid) Condensation Rain clouds Transpiration from plants Transpiration Precipitation Precipitation Evaporation Precipitation to ocean Evaporation From ocean Infiltration and percolation Surface runoff (rapid) Groundwater movement (slow) Ocean storage Groundwater movement (slow) What type of System is this? Name the inputs, outputs, transfers and transformations

7. The cycling of matter. Because there are only finite amounts of nutrients available on the earth, they must be recycled in order to ensure the continued existence of living organisms. Examples are the: Water Cycle http://www.youtube.com/watch?v=0_c0ZzZfC8c

8. The cycling of matter. Because there are only finite amounts of nutrients available on the earth, they must be recycled in order to ensure the continued existence of living organisms. Examples are the: Carbon Cycle http://www.youtube.com/watch?v=OByqdUhWERk

10. The cycling of matter. Because there are only finite amounts of nutrients available on the earth, they must be recycled in order to ensure the continued existence of living organisms. Examples are the: Nitrogen Cycle http://www.youtube.com/watch?v=w03iO_Yu9Xw

11. The cycling of matter. Because there are only finite amounts of nutrients available on the earth, they must be recycled in order to ensure the continued existence of living organisms. Examples are the: Phosphorus Cycle http://www.youtube.com/watch?v=Au0ZaqXy1wM

12. The flow of solar energy into the earth's systems. As radiant energy, it is used by plants for food production. As heat, it warms the planet and powers the weather system. Eventually, the energy is lost into space in the form of infrared radiation. Most of the energy needed to cycle matter through earth's systems comes from the sun.

13. Thermodynamics is the study of the energy transformations that occur in a system. 2 Laws of thermodynamics: • Energy can be transferred and transformed, but it cannot be • created or destroyed. It follows the law of conservation of • energy (physics) and it describes how the energy of the • universe is constant. • In an isolated system, the total amount of entropy (disorder) will tend to increase. (This results in the loss of het energy)

14. Any conversion of energy is less than 100% efficient and therefore Some energy is wasted or lost. Usually this energy is lost in the form of heat. Only 25% of the energy stored in gasoline is transformed in the motion of a car, 75% is lost as heat.

15. Pyramid of energy is always upright. It is so because at each transfer about 80 - 90% of the energy available at lower trophic level is used up to overcome its entropy and to perform metabolic activities. Only 10% of the energy is available to next trophic level (as per Lindemann's ten percent rule).

16. Equilibrium: a state of balance between parts of a system • There are fluctuations in a system, however most systems return to a balanced state after a disturbance. • Steady-state equilibrium – allows system to go to a steady state after disturbance (ex: mammals regulate body temperature, population of animals in an ecosystem, tree falling in forest) Steady-state equilibrium

17. Static Equilibrium: • no changes over time • no inputs or outputs to system • non-living • ex: rock formations over time, bottle sitting on table

18. Homeostasis = The property of a system, that regulates its internal environment and tends to maintain a stable, constant condition. Negative Feedback = The way living systems maintain homeostasis. Negative feedback systems include a sequence of events that will cause an effect that is in the opposite direction to the original stimulus and thereby brings the system back to its equilibrium position.

19. Predator Prey relationships are usually controlled by negative feedback where: Increase in Prey  Increase in Predator  Decrease in Prey  Decrease in Predator  Increase in Prey  and so on in a cyclical manner

23. Positive feedback systems include a sequence of events that will cause an effect that is in the same direction to the original stimulus and thereby brings the system further away from equilibrium. • Example: Exponential population growth • Eventually the positive feedback reaches a tipping point and is unstable. At this point a new equilibrium must form.

24. Which of the populations show positive feedback? Which of the populations show negative feedback?

25. Positive or Negative Feedback? • If a pond ecosystem became polluted with nitrates, washed off agricultural land by surface runoff, algae would rapidly grow in the pond. The amount of dissolved oxygen in the water would decrease, killing the fish. The decomposers that would increase due to the dead fish would further decrease the amount of dissolved oxygen and so on... • A good supply of grass for rabbits to eat will attract more rabbits to the area, which puts pressure on the grass, so it dies back, so the decreased food supply leads to a decrease in population because of death or out migration, which takes away the pressure on the grass, which leads to more growth and a good supply of food which leads to a more rabbits attracted to the area which puts pressure on the grass and so on and on....

26. Equilibrium generally maintained by negative feedback – inputs should equal outputs

27. Systems are defined by the source and ultimate destination of their matter and/or energy. Open system = A system in which both matter and energy are exchanged across boundaries of the system. Closed system = A system in which energy is exchanged across boundaries of the system, but matter is not. Isolated system = A system in which neither energy or matter is exchanged across boundaries of the system. No such system exists.