What’s the link between these species?

5. What’s the link between these species?

6. Myxomatosis in Australia

7. Conclusions • These examples illustrate the complexity of ecology. • They also suggest that it is not enough to study species in isolation.

8. Systems • A system is an assemblage of parts, working together, forming a functional whole. • Many types exist from cells, to people, to cars, to economies to the whole planet. • Reductionist vs systems approach

9. Scales of systems • Systems occur on different scales. • Individual organism • Ecosystem • Biome • Planet • Universe

10. Classifying systems • Open – exchange matter and energy • Closed – exchange energy • Isolated – exchanges neither

11. Making our own system www.essib.com

12. Biosphere II

13. Thermodynamics • 1st law of thermodynamics: energy is neither created nor destroyed. • Therefore, in an isolated system (the universe) energy is constant. • Energy is transformed into different forms, e.g. from solar to chemical energy in food. • 2nd law of thermodynamics: in any isolated system entropy tends to increase spontaneously. • This means energy and materials go from a concentrated into a dispersed form.

14. Thermodynamics • 1st law of thermodynamics: energy is neither created nor destroyed. • Therefore, in an isolated system (the universe) energy is constant. • Energy is transformed into different forms, e.g. from solar to chemical energy in food. • 2nd law of thermodynamics: in any isolated system entropy tends to increase spontaneously. • This means energy and materials go from a concentrated into a dispersed form. • What does this mean for living organisms?

15. Summary • The world can be studied using a reductionist or systems approach: both have merits. • A system is an assemblage of parts, working together, forming a functional whole. • Systems can be small or large. • Systems can be classified as open, closed or isolated. • Thermodynamics: 1st and 2nd laws have implications for the maintenance of living systems.

16. Communication Edmodo code: 4nuu62 Website: www.essib.com Email: tmartell@parksidefederation.org.uk

17. Properties of systems • Equilibria • Flows and storages • Feedback processes – how do they influence equilibria? • Transfer and transformation processes

18. Equilibria

19. Equilibria A static equilibrium is a state in which nothing changes. These are uncommon in nature. A steady-state equilibrium is where there are continuous inputs and outputs but the overall system remains the same. Over a long period there can be large changes in the equilibrium position.

20. Flows and storages Storages Inputs Outputs Flows Flows Solar Glucose (chemical energy) Heat

21. Feedback Positive feedback leads to a change in the equilibrium state. It accelerates deviation. Negative feedback leads to a maintenance of the equilibrium state. It counteracts deviation, for example, predator-prey relations. There is always a time lag.

22. Negative feedback

23. Transfer and transformation • Transfers flow through a system and lead to a change in location. • Transformations lead to an interaction within a system in the formation of a new end product. • Dead organic matter entering a lake is a transfer process; decomposition of this material is a transformation process.

24. Task Make a diagram to describe your model ecosystem. Include: • Feedback processes involved • Transfer and transformation processes • Flows and storages • What kind of an equilibrium is your system in?

25. Good morning! Please get out your homework and put it on the desk. We are going to start the lesson by looking at each other’s work. • When listening to others consider the following • Would you add anything to their model? • Is anything about their model unrealistic? • Is there model quantitative? • What assumptions does their model make? Extension: • Does it matter how realistic the model is? • Are there situations where it really matters that we use good models?

26. What is a model and why do we use them? • A model is a representation of the world. • The real world is very complicated, but by using models we can start to understand the interactions that occur in a system. • What is the difference between quantitative and qualitative?

27. Model example 1

28. Model example 2

29. Model example 3 • “If I don’t do my homework. The teacher will be angry and give me a detention”. • We all make models like this in our head every day. Can you think of any models that we make?

30. Model 4

31. When does it matter how accurate models are? • Weather models – shipping, aircraft, fishing, crops. • Economic models – impact on people’s lives. • Climate models – action on global warming. • What other models can you think of when it matters how accurate they are?

32. Evaluating models “All models are wrong, but some models are useful.” George Box, 1919-2013

33. Making a better model • Choose your own system. • Your task is to produce a presentation to explain your model. • It should include everything we have looked at so far. • The nature of any equilibria – and how resilient it might be to change. • Your model should ideally be quantitative. • Carefully consider and justify any assumptions you make.

34. Questions • What is the difference between negative and positive feedback? • Give an environmental example of positive feedback. • What is meant by transfer within a system? How does this differ from transformation? • Draw a systems diagram showing the inputs, outputs and storages of a tree. • Compile a table with the strengths and weaknesses of using models.

35. Extra reading • Essential • Weebly • Email addresses • Fun! • Can also be documentaries and books.