Significant Ideas
The laws of thermodynamics govern the flow of energy in a system and the ability to do work.
Systems can exist in alternative stable states or as equilibria between which there are tipping points.
Destabilizing positive feedback mechanisms will drive systems toward these tipping points, whereas stabilizing negative feedback mechanisms will resist such changes.
Knowledge and Understanding
The first law of thermodynamics is the principle of conservation of energy, which states that energy in an isolated system can be transformed but cannot be created or destroyed.
The principle of conservation of energy can be modeled by the energy transformations along food chains and energy production systems.
The second law of thermodynamics states that the entropy of a system increases over time. 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.
The second law of thermodynamics explains the inefficiency and decrease in available energy along a food chain and energy generation systems.
As an open system, an ecosystem will normally exist in a stable equilibrium, either in a steady-state equilibrium or in one developing over time (for example, succession), and maintained by stabilizing negative feedback loops.
Negative feedback loops (stabilizing) occur when the output of a process inhibits or reverses the operation of the same process in such a way as to reduce change—it counteracts deviation.
Positive feedback loops (destabilizing) will tend to amplify changes and drive the system toward a tipping point where a new equilibrium is adopted.
The resilience of a system, ecological or social, refers to its tendency to avoid such tipping points and maintain stability.
Diversity and the size of storages within systems can contribute to their resilience and affect their speed of response to change (time lags).
Humans can affect the resilience of systems through reducing these storages and diversity.
The delays involved in feedback loops make it difficult to predict tipping points and add to the complexity of modeling systems.
Applications and Skills
Explain the implications of the laws of thermodynamics to ecological systems.
Discuss resilience in a variety of systems.
Evaluate the possible consequences of tipping points.
Guidance
The use of examples in this sub-topic is particularly important so that the abstract concepts have a context in which to be understood.
Emphasis should be placed on the relationships between resilience, stability, equilibria and diversity.
A stable equilibrium is the condition of a system in which there is a tendency for it to return to the previous equilibrium following disturbance.
A steady-state equilibrium is the condition of an open system in which there are no changes over the longer term, but in which there may be oscillations in the very short term.
A tipping point is the minimum amount of change within a system that will destabilize it, causing it to reach a new equilibrium or stable state.
Examples of human impacts and possible tipping points should be explored.
Key Vocabulary
Here
Textbook Reading and/or Activities
Pages 4-9
Case Study (p.7)
Case Study (p.8)
Exercises (p.9)
Notes
i-Biology Notes (Not available)
A detailed set of notes, created by Stephen Taylor, examining UX - UY and AX - AY.
i-Biology Study Questions (Not available)
A series of questions, created by Stephen Taylor, to help check your understanding of the IB learning expectations. This is VERY GOOD practice.
Bioknowledgy Notes (Not available)
A detailed set of notes, created by Chris Paine, examining all of the IB learning expectations.
Bioknowledgy Study Questions (Not available)
A series of questions, created by Chris Paine, to help check your understanding of the IB learning expectations. This is VERY GOOD practice.
Learning Activities
Resource
Description
Supplemental Reading
Resource
Description
This video outlines concepts K&U 8-9 and A&S 2.
This video outlines concepts K&U 5-7 but there is no need to watch past the 8:15 mark.
This video outlines concepts K&U 5-7.
This video outlines the concepts examined throughout most of the K&U section of this page.
Should Watch Videos
This video outlines concepts K&U 6-11 and A&S 2-3.
This video outlines concepts K&U 1-5 and A&S 1.
Must Watch Videos
This video outlines concepts K&U 10-11 and A&S 3.