1. Energy and Equilibria

2. Energy
Ecosystems maintain themselves by cycling energy and nutrients obtained from external sources

3. Energy
An example of the concept of energy flow through trophic levels of a food chain.

4. The laws of energy in an ecosystem
1st Law of Thermodynamics
2nd Law of Thermodynamics

5. 1st law of thermodynamics are relevant to environmental systems
1st Law = Energy is neither created or destroyed.
In nature energy comes in as sunlight, passes along as biomass, and exits as heat bit by bit.

6. 1st law of thermodynamics are relevant to environmental systems
The amount of energy within a system is constant. The form of the energy however changes.

7. System Processes Two basic processes must occur
1. Cycling of chemical elements
2. Flow of energy

8. System Processes
1. Transfer- Basic flow through a system. Change in location of energy or matter
Ex. Water rushing down a hill

9. System Processes
2. Transformation- A new product is created. Change of state (solid, liquid, gas).
Ex. Water evaporating into water vapor

10. 1st law of thermodynamics are relevant to environmental systems
Producers transform light energy from the sun into chemical energy (photosynthesis)
Consumed and transferred to other organisms (respiration)
Eventually dead organism are broken down by decomposers and nutrients are returned to the soil.

11. 1st law of thermodynamics are relevant to environmental systems
Energy is lost as heat to the atmosphere during this process but is not lost to the system.

12. 2nd law of thermodynamics are relevant to environmental systems
2nd Law = Energy goes from a concentrated form into a dispersed form.

13. 2nd law of thermodynamics are relevant to environmental systems
Available energy decreases with time as order takes energy.

14. 2nd law of thermodynamics are relevant to environmental systems
Energy transfer is not 100% effective.
There is less and less available energy in each successive level.

15. Entropy
The entropy of an isolated system not in equilibrium will tend to increase over time.
In other words, the randomness (entropy) of the universe is always increasing
Entropy is a measure of the amount of disorder in a system.
An increase in entropy arising from energy transformations reduces the energy available to do work.

16. Entropy
When energy conversions take place they are not 100% efficient and some energy is wasted as heat energy.

17. Entropy
Within any food web the amount of energy that is found in the producers is much more than that found in the top carnivores (tertiary etc…).
As energy is transferred and transformed from one organism to the next (moves up the trophic levels) energy is lost as heat.

18. Entropy
When a loin chases a zebra, the zebra attempts to escape, changing stored chemical energy into useful work
During its attempt to escape some of the stored energy is converted to heat and lost from the food chain.
Energy = work + heat (and other wasted energy)

19. Demonstrating Energy Conversion 2nd Law
Calculating the percent of energy transferred
Divide energy from the second trophic level by the energy from the first trophic level.
Multiply by 100

20. Demonstrating Energy Conversion 2nd Law
Pour 1000 mL of tap water into the 1000 mL beaker. Add 2 drops of food coloring to the water and swirl. The water in this beaker represents the energy found in the first trophic level (producers)

21. Demonstrating Energy Conversion 2nd Law
Line up 3 clear cups. How much energy was transferred from trophic level one to trophic level 2?
Pour that percentage from the 1000 mL into the first cup.

22. Demonstrating Energy Conversion 2nd Law
How much energy was transferred from the second trophic level to the third?
Pour that percentage from cup one into cup two.
Repeat for the fourth trophic level/cup three.

23. Flow of Energy
Flow of energy through a ecosystem can be shown as an Ecological Pyramid

24. Equilibria

25. Types of Equilibria
Equilibrium refers to a state of balance in an ecosystem
Steady state
Static

26. Nature of equilibria
Steady-state equilibrium – Maintains a stable system due to constant flow of inputs and outputs
Steady-state equilibrium refers to an ecological system because such a system requires inputs and outputs in order to function. .

27. Nature of equilibria
Static equilibrium - doesn't’t apply to natural systems as there are no inputs or outputs so no change occurs.
Static – always in balance
Inanimate objects

28. Nature of equilibria Stable – Returns to balance after disturbance
Rubber
Unstable – Achieves new balance after disturbance
Car Crash

29. Nature of equilibria
A system that is an unstable equilibrium and faces a disturbance will not return to the original equilibrium and establish a new one.
As long as there is sunlight, plants can perform the process of photosynthesis, however when night time comes, plants must adopt a new equilibrium to produce food, this equilibrium is known as respiration.

30. Principles of positive and negative feedback
Ecosystems are said to be “Self-regulating”
Each contain feedback mechanisms which function to maintain the system in its equilibrium state.
Positive
Negative

31. Principles of positive and negative feedback
Negative Feedback – dampens effects and promotes return to stability
Predator-prey relationships

32. Principles of positive and negative feedback
Positive Feedback – Amplifies change and leads to deviation from stability
Temperature and greenhouse gases

33. Principals of Positive and Negative Feedback

34. Resilience The capacity of an ecosystem to respond to a disturbance.
Absorb disturbance without shifting to an alternative state and losing function and services. conditions

35. Resilience Disturbances can include Fires Flooding Windstorms
Insect population explosions
Deforestation
Fracking
Pesticide

36. Resilience
Some disturbances can significantly affect an ecosystem and can cause an ecosystem to reach a threshold beyond which some species can not recover.
Reduction of biodiversition
Exploitation of natural resources
Pollution
Land-use

37. Tipping Point
Positive Feedback tends to amplify and drive a system toward a tipping point
Minimum amount of change within a system that will destabilize it, causing it to reach a new equilibrium or stable state.

38. Tipping Point
At a particular moment in time, a small change within a global climate system can transform a relatively stable system to a very different state of the climate

39. Identifying what phenomena are capable of passing tipping points can be tricky.
“Tipping elements” is used to describe large-scale components of the Earth System which may be subject to tipping points.
Arctic Sea Ice
Ice Sheets
El Nino
Amazon Rain Forest

40. Tipping Point