IB ESS HL 1.2 Systems Questions

Practise IB ESS HL 1.2 by evaluating system models, feedback loops and resilience under competing environmental pressures.

Exam points

construct and interpret system diagrams by linking storages, inputs and outputs with transfers, transformations and directional cause-and-effect flows
classify open and closed systems by matter and energy exchange, then use Earth-system and Gaia evidence to explain interdependence and regulation
trace positive and negative feedback through equilibrium, amplification, tipping points and alternative stable states in ecological or social systems
evaluate models and model projections by weighing their simplified representation, predictive use, assumptions, input data and uncertainty
judge resilience by linking diversity, storage size, time lags and human disturbance to resistance, recovery and ecosystem stability

Covered syllabus points

1.2.1—Systems definition 1.2.2—Systems approach 1.2.3—System diagrams 1.2.4—Types of flows 1.2.5—Open vs. closed systems 1.2.6—Earth as integrated system 1.2.7—System scales 1.2.8—Negative feedback loops 1.2.9—Stable equilibrium in ecosystems 1.2.10—Positive feedback loops 1.2.11—Tipping points 1.2.12—Tipping point effects 1.2.13—Models 1.2.14—Model limitations 1.2.15—Emergent properties 1.2.16—System resilience 1.2.17—Factors affecting resilience 1.2.18—Human impacts on resilience

[Maximum number: 20]

(a)

Outline how four different factors influence the resilience of an ecosystem.

[ 4 ]

(b)

Explain how a community of trees in a woodland may be considered a system.

[ 7 ]

(c)

Disturbance of the composition and processes of the atmospheric system through human activity always disturbs the equilibria of marine systems.

Discuss the validity of this statement with reference to named examples.

[ 9 ]

• understanding concepts & terminology of greenhouse gases; global warming; thermal expansion; rising sea-level; melting ice caps; salinity; ocean acidification; ozone depletion; UV radiation; global productivity; tropospheric ozone; acid rain (worth noting here that acid rain is NOT a significant cause/contributor to ocean acidification); etc
• breadth in addressing and linking impacts on atmospheric systems (increased $\mathrm{CO}_{2}$ ; global warming; ozone depletion; tropospheric ozone; acid rain; etc) with disturbances in marine systems (rising sea level; ocean currents; fish migration; acidification; destruction of coral reefs; phytoplankton / marine food chains; etc)
• examples of relevant atmospheric pollutants/disturbances; ocean currents; coral communities; migratory fish; marine food chains; etc
• balanced analysis of the extent to which each atmospheric disturbance causes disturbance in marine systems whether significant, minimal or none at all, acknowledging relevant counter-arguments/alternative viewpoints;
• a conclusion that is consistent with, and supported by analysis and examples given e.g. generally, the statement is valid regarding large scale disturbances to the atmosphere such as global warming and ozone depletion but more localized disturbances like tropospheric ozone and acid rain have fairly minimal impact;

The following guide for using the markbands suggests certain features that may be offered in responses. The five headings coincide with the criteria given in each of the markbands (although "ESS terminology" has been conflated with "Understanding concepts"). This guide simply provides some possible inclusions and should not be seen as requisite or comprehensive. It outlines the kind of elements to look for when deciding on the appropriate markband and the specific mark within that band.

NB This is only an example of a possible conclusion. Candidates' conclusions do not have to agree.
Use the official Section B, part (c) markbands below.

Marks	Level descriptor
0	The response does not reach a standard described by the descriptors below and is not relevant to the question.
1–3	The response contains: • minimal evidence of knowledge and understanding of ESS issues or concepts • fragmented knowledge statements poorly linked to the context of the question • some appropriate use of ESS terminology • no examples where required, or examples with insufficient explanation/relevance • superficial analysis that amounts to no more than a list of facts/ideas • judgments/conclusions that are vague or not supported by evidence/argument.
4–6	The response contains: • some evidence of sound knowledge and understanding of ESS issues and concepts • knowledge statements effectively linked to the context of the question • largely appropriate use of ESS terminology • some use of relevant examples where required, but with limited explanation • clear analysis that shows a degree of balance • some clear judgments/conclusions, supported by limited evidence/arguments.
7–9	The response contains: • substantial evidence of sound knowledge and understanding of ESS issues and concepts • a wide breadth of knowledge statements effectively linked with each other, and to the context of the question • consistently appropriate and precise use of ESS terminology • effective use of pertinent, well-explained examples, where required, showing some originality • thorough, well-balanced, insightful analysis • explicit judgments/conclusions that are well-supported by evidence/arguments and that include some critical reflection.

Section B, part (c) markbands (official markscheme p16)

[Maximum number: 4]

(a)

The soil system includes storages of inorganic nutrients.

[ 4 ]

(i)

Identify two inputs to these storages.

[ 2 ]

(ii)

Identify two outputs from these storages.

[ 2 ]

[Maximum number: 4]

Draw a system diagram to illustrate the impact of acid deposition on an ecosystem.

[Maximum number: 7]

Explain how a community of trees in a woodland may be considered a system.

[Maximum number: 2]

Figure:Representation of the water cycle

Identify one transfer and one transformation process shown in the water-cycle diagram above.

Transfer:
Transformation:

[Maximum number: 1]

Figure:Simplified map of the Lake Shergar area

Figure 3: A simplified diagram of the Lake Shergar area.

The lake provides a water supply for the local population.

Outline why this lake may be considered an open system.

[Maximum number: 4]

Outline the Gaia hypothesis as a model of the global ecosystem.

Gaia hypothesis views Earth as a self-regulating system/homeostatic system/living organism;
...maintaining life-supporting conditions/equilibrium;
...through negative feedback mechanisms;
...eg where any changes in global temperature/ocean salinity/ $\mathrm{O}_{2}$ concentration stimulate mechanisms to inhibit/reverse that change;
living organisms interact with non-living elements to form habitable conditions on Earth / it proposes that the evolution of life on earth stabilised global temperatures/atmospheric composition/ocean salinity making the planet more habitable;
eg "Daisy World" where high temperatures promote growth of more reflective daisies;
humans are part of the living system, do not dominate it or have any intrinsic right of exploitation / but may contribute to positive feedback mechanisms destabilising equilibrium in the short term;

[Maximum number: 3]

Explain how predation may lead to:

stability in a population of the prey species.

[Maximum number: 9]

Steady state equilibrium is a concept relevant to many systems. Justify its usefulness in understanding the sustainability of named systems.

Answers may demonstrate:
- understanding concepts & terminology of steady state equilibrium; short-term oscillations; long-term stability; systems approach; holistic view; open/closed systems; storages; flows; balanced inputs & outputs; balanced processes (transfers & transformations); laws of thermodynamics; tipping points; stable equilibrium; negative & positive feedback; ecosystem resilience; sustainable development definition; life-supporting services; food webs; population dynamics; S curve; carrying capacity; cycles of matter; flow of energy; mean global temperature; natural income; natural capital; MSY (maximum sustainable yield); environmental/social/economic sustainability;
- breadth in addressing the concept of steady state equilibrium (SSE) as applied to a range of natural and/or anthropogenic systems and linking to how this concept contributes to understanding sustainability as the quest of human societies to achieve long-term stability (meeting the need of future generations), despite inevitable short-term fluctuations in the process of meeting present needs.
- examples of different steady state equilibria occurring in a range of natural & anthropogenic systems, e.g. predator-prey cycles, fluctuation around carrying capacity, disturbance-prone ecosystems, nutrient cycling, timber harvesting, fisheries, crop/meat production, energy use, water extraction, etc. or unsustainable examples deviating from SSE; e.g. deforestation, overfishing, global climate change, pollution, habitat loss, overconsumption etc..
- balanced analysis providing evidence supporting the idea that the concept of 'steady state equilibrium' is useful in understanding how various aspects of sustainability may be achieved in a range of systems. [Note to examiners: not how equilibrium is achieved in sustainable systems or how unsustainable systems deviate from equilibrium/balance. Still, such examples are implicitly linked to the context of the question].
- a conclusion that is consistent with, and supported by analysis and examples given e.g. Steady state equilibrium is inherent in the sustainable management and responsible use of natural capital. Short-term fluctuations are inevitable, as, for example, catching fish at a rate observing MSY, reduces temporarily the population, but soon it will regenerate through reproduction. Understanding that the important issue is to maintain the long-term stability of natural capital would help achieving sustainability of a system like wild fisheries.

[Maximum number: 2]

Outline how a reduction in snow cover in the Alps can act as a positive feedback loop for climate change.

[Maximum number: 4]

Outline how feedback loops are involved in alternate stable states and the tipping points between them.

[Maximum number: 1]

Figure 1: Three projections for world population from the present day to 2100.

The chart shows three projections for world population to 2100. The lines represent high, medium and low population estimates.

Outline one advantage of modelling future human population sizes.

[Maximum number: 1]

Figure 2: Observed and projected changes in global stratospheric ozone

Figure:Observed and projected changes in global stratospheric ozone

Key:
- Annually averaged data
- Average of atmospheric model projections

Outline one factor that may affect the reliability of the model projections in Figure 2.

[Maximum number: 3]

Figure:Building back better

Dominica is focusing on a “Building back better” programme of recovery after Hurricane Maria to:
• become the world’s first climate-resilient nation
• conduct disaster risk assessment before reconstruction
• build hurricane-proof buildings
• build using local skills and resources
• focus on community participation in reconstruction
• plant fast-growing crops, such as lettuce and Chinese cabbage
• focus on root crops, such as sweet potatoes and ginger
• plant heat-tolerant varieties of foods
• keep farm animals in air-conditioned buildings.

Using information from Figure 5, outline how the “Build back better” programme can contribute to the resilience of Dominica.

[Maximum number: 4]

Outline how four different factors influence the resilience of an ecosystem.

[Maximum number: 9]

Discuss the role of humans in the destabilization of ecological systems.

Answers may include:
• understanding concepts and terminology of steady state and dynamic equilibria, stability, resilience, tipping-points, diversity, storage size, productivity, negative/positive feedback, complexity, community interdependence/interaction, human impacts of overexploitation/unsustainable harvesting, pollution, habitat degradation/destruction, unsustainable development, etc
• breadth in addressing and linking factors that provide stability/resilience eg storage size, diversity, productivity, complexity, etc with human activities that either weaken/reduce them eg overfishing, intensive agriculture, C emissions/global warming, water/atmospheric pollution, deforestation, urbanisation, mining/resource extraction, etc or activities that strengthen/protect them eg legislation setting pollution limits/standards/fishing quotas, sustainable development schemes, alternative/renewable energies, conservation efforts/reserves, etc
• examples of specific negative impacts on stability of ecological systems e.g. overfishing reduces the storage size of targeted fish populations reducing their stability, C emissions lead to climate change that reduces primary productivity of systems, eutrophication will interfere with negative feedback loops in freshwater systems, atmospheric pollutants may eliminate sensitive species of lichen reducing diversity, etc and positive impacts on stability e.g. in-situ conservation protects complexity of relationships in system, agricultural techniques conserving soils maintain high productivity, etc
• balanced analysis of the extent to which human activities promote or prevent destabilisation of ecological systems with acknowledgement of relevant counter-arguments/alternative viewpoints.
• a conclusion that is consistent with, and supported by, analysis and examples given eg "The role of humans in destabilising ecological systems is very diverse, and with the current size and growth of population, the magnitude of that role is becoming immense, calling for urgent and wide-scale efforts to adopt a proactive role in re-stabilising those systems." NB This is only an example of a possible conclusion. Candidates' conclusions do not have to agree. Their value should be assessed simply according to the criteria given in the markband descriptors.

Marks	Level descriptor
0	The response does not reach a standard described by the descriptors below and is not relevant to the question.
1–3	The response contains: • minimal evidence of knowledge and understanding of ESS issues or concepts • fragmented knowledge statements poorly linked to the context of the question • some appropriate use of ESS terminology • no examples where required, or examples with insufficient explanation/relevance • superficial analysis that amounts to no more than a list of facts/ideas • judgments/conclusions that are vague or not supported by evidence/argument.
4–6	The response contains: • some evidence of sound knowledge and understanding of ESS issues and concepts • knowledge statements effectively linked to the context of the question • largely appropriate use of ESS terminology • some use of relevant examples where required, but with limited explanation • clear analysis that shows a degree of balance • some clear judgments/conclusions, supported by limited evidence/arguments.
7–9	The response contains: • substantial evidence of sound knowledge and understanding of ESS issues and concepts • a wide breadth of knowledge statements effectively linked with each other, and to the context of the question • consistently appropriate and precise use of ESS terminology • effective use of pertinent, well-explained examples, where required, showing some originality • thorough, well-balanced, insightful analysis • explicit judgments/conclusions that are well-supported by evidence/arguments and that include some critical reflection.

Section B, part (c) markbands (MS p15)

All question bank results loaded

Covered syllabus points

Question 1

Question (a)

Question (b)

Question (c)

Question 2

Question (a)

Question (i)

Question (ii)

Question 3

Question 4

Question 5

Question 6

Question 7

Question 8

Question 9

Question 10

Question 11

Question 12

Question 13

Question 14

Question 15

Question 16