Identify the type of equilibrium represented in panel A.

Describe two features of stable equilibrium shown in panel B.

Identify the Earth-system sphere containing each of the following: mountain snow and exposed soil.

Explain the change in river turbidity between the period before the wildfire and month 1.

Explain why Earth is considered to approximate a closed system rather than an open system.

Evaluate the usefulness of representing the wildfire as an integrated Earth system.

Identify the approximate phosphorus concentration at which the lake shifts to a high-algal-biomass state as phosphorus is increased.

Compare the algal biomass at a phosphorus concentration of $0.04\ \text{mg}$ per litre during the increasing- and decreasing-phosphorus treatments.

Explain how the pattern in Figure 4 demonstrates a tipping point and a regime shift.

Calculate the percentage of annual anthropogenic carbon emissions that accumulates in the atmosphere.

Explain why Earth approximates a closed system for matter but not for energy.

Analyse how the anthroposphere can cause linked changes in three other Earth-system components shown in Figure 5.

Draw a systems diagram for this pond.

Explain how melting sea ice can form a positive feedback loop that amplifies an initial increase in temperature.

Calculate the percentage increase in chlorophyll-a concentration when phosphorus loading increased from 0.60 to $0.65\ \text{mg m}^{-2}\text{ day}^{-1}$.

Explain why the change at a phosphorus loading of approximately $0.65\ \text{mg m}^{-2}\text{ day}^{-1}$ may be described as a tipping point.

Explain one positive feedback loop that maintains the turbid state.

Evaluate the proposal that reducing external phosphorus loading to $0.50\ \text{mg m}^{-2}\text{ day}^{-1}$ would restore the lake to its clear-water state.

Calculate the percentage decrease in summer sea-ice area between temperature anomalies of 0 K and 3 K.

Describe the relationships between sea-ice area, surface albedo and absorbed solar energy.

Explain how the relationships in Figure 6 form a positive feedback loop.

Suggest one feature of Figure 6 that may indicate movement towards a tipping point.

Determine which model most closely matches the observations and calculate its absolute prediction error in year 10.

Explain how the feedbacks included in Model C account for its pattern after the drought.

Evaluate the use of Model C to predict the response of other forests to drought.

Outline four features that should be identified when applying a systems approach to the composting facility.

Using named examples, evaluate the usefulness of a systems approach in improving the sustainability of urban organic-waste management.

Explain how negative feedback produces the temperature pattern for the living Daisyworld.

Explain one advantage of using this model rather than manipulating an entire forest.

Explain one limitation of its prediction.

Outline two ways in which changing the boundary from the local pool to the river catchment would alter the systems model.

Outline why decomposition within the local pool may be represented as only one aggregated flow in a global model.

Calculate the difference between the temperature increases of the lifeless planet and living Daisyworld from relative stellar radiation 0.85 to 1.15.

Explain how negative feedback regulates the temperature of Daisyworld as stellar radiation increases.

Explain how the Daisyworld results support the regulatory principle of the Gaia hypothesis.

Evaluate the usefulness of Daisyworld as a model for predicting temperature regulation on Earth.

Calculate the daily change in reservoir storage under the representative pre-management dry-season conditions.

Explain why the reservoir was not in steady-state equilibrium under the pre-management conditions shown in the water-budget table.

Analyse how the management measures may have contributed to the change in reservoir storage by year 5.

Explain why a systems approach is more appropriate than considering the reservoir storage in isolation.

Evaluate the conclusion that seasonal pricing and leakage repairs caused the increase in reservoir storage.

Explain how interactions among three named Earth-system spheres demonstrate that Earth is an integrated system.

Explain how the Daisyworld model represents temperature regulation by negative feedback.

Evaluate the Gaia hypothesis as a model for understanding regulation within the Earth system.

Distinguish between stable equilibrium and steady-state equilibrium in an open ecosystem.

Explain how negative feedback may contribute to the recovery of a forest ecosystem after a severe storm reduces its plant biomass.

Using named examples, to what extent do negative feedback loops maintain the stability of ecosystems exposed to human disturbance?

Explain how crossing the tipping point can cause a regime shift from the clear-water state to the turbid state.

Determine the percentage of incoming radiation absorbed by sea ice and by open ocean.

Explain how the ice–albedo feedback can amplify an initial decrease in sea-ice cover.

Analyse the evidence that the model contains a tipping point.

Evaluate the use of this model to guide decisions about polar-climate policy.

Explain the relationship between positive feedback, a tipping point and a regime shift.

Analyse how repeated heat stress could cause a coral-dominated reef to undergo a regime shift to an algae-dominated state.

Using named examples, evaluate the usefulness of system models for predicting and managing environmental tipping points.

Outline four characteristics of a model used to represent an environmental system.

Analyse how changing the model boundary and spatial scale could affect the coastal city's flood-risk assessment.

Using named examples, evaluate the use of models at different scales to guide management of environmental hazards.

Explain why Earth may be considered approximately closed for matter but open for energy.

Analyse how thawing permafrost can create linked changes across the integrated Earth system.

Using named examples, to what extent does a systems approach improve decisions intended to reduce climate-related environmental change?