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Understanding IB Environmental Systems and Societies (ESS) command terms is essential for success in the course, as these terms determine the type of responses expected in your exams. Simply knowing environmental concepts is not enough – you must also understand exactly what the examiner is asking you to do since each command term requires a different style of response. In this guide, we'll break down the most important IB ESS command terms and show you how to answer each one effectively.
IB ESS Command Terms
Define – Give the precise meaning of a word, phrase or quantity. For example, if you were asked to define ecological footprint, an appropriate answer would be: "An ecological footprint is the amount of biologically productive land and water required to provide the resources consumed and absorb the wastes produced by an individual, population, or activity."
Draw – Represent a diagram or graph accurately, using labels unless instructed otherwise. For example, if you were asked to draw the carbon cycle, you should include major carbon stores (such as the atmosphere, oceans, vegetation, and fossil fuels) and clearly label the processes that transfer carbon between them, including photosynthesis, respiration, combustion, and decomposition.
Label – Add labels to a diagram. For example, if you were given a diagram of a freshwater ecosystem, you would label the producers, consumers, decomposers, sunlight, nutrients, and other relevant components indicated on the diagram.
List – Give a sequence of brief answers with no explanation. For example, if asked to list the main greenhouse gases, you would write:
- Carbon dioxide
- Methane
- Nitrous oxide
- Water vapour
No further explanation is required.
Measure – Obtain a value for a quantity. For example, during an ESS field investigation, you may be asked to measure the pH of a water sample using a pH probe or test kit and record the value accurately.
State – Give a brief answer without explanation. For example:
State one renewable source of energy.
Answer: Solar energy.
Annotate – Add brief explanatory notes to a diagram or graph. For example, you may annotate a food web by identifying producers, primary consumers, and decomposers while briefly explaining the direction of energy flow.
Apply – Use knowledge or principles in a new situation. For example, if asked to apply the concept of carrying capacity to a national park, you would explain how exceeding the park's carrying capacity could result in habitat degradation, increased pollution, and declining biodiversity.
Calculate – Find a numerical answer, showing your working. For example, you may be asked to calculate percentage biodiversity loss or determine population growth rate using data provided in a table.
Describe – Give a detailed account. For example, if asked to describe ecological succession, you should explain how an ecosystem changes over time from pioneer species through intermediate communities to a stable climax community.
Distinguish – Make clear the differences between two or more concepts. For example, if asked to distinguish between renewable and non-renewable resources, you should explain that renewable resources can be replenished naturally within a human timescale, whereas non-renewable resources cannot.
Estimate – Give an approximate value. For example, you may estimate the percentage of forest cover shown on a satellite image or approximate carbon emissions from a graph.
Identify – Select the correct answer from the information provided. For example, after examining a graph of atmospheric carbon dioxide concentrations, you may be asked to identify the year with the highest recorded concentration.
Outline – Give a brief summary. For example, if asked to outline the process of eutrophication, you would briefly mention nutrient enrichment, algal bloom formation, oxygen depletion, and the resulting effects on aquatic organisms.
Analyse – Interpret data to reach conclusions. For example, if given data showing changes in fish populations over time, you would identify trends, compare values, and explain what the data suggests about ecosystem health or human impacts.
Comment – Give a judgment based on evidence provided. For example, after calculating the ecological footprint of two countries, you may comment on which country appears to use resources more sustainably and support your conclusion using the data.
Compare – Give similarities and differences, referring to both throughout your answer. For example, compare intensive agriculture with sustainable agriculture by discussing productivity, environmental impacts, biodiversity, and long-term sustainability.
Construct – Represent or develop information in graphical form. For example, you may be asked to construct a line graph showing changes in atmospheric carbon dioxide concentrations over time using the data provided.
Deduce – Reach a conclusion using the information given. For example, if dissolved oxygen levels decrease while nutrient concentrations increase, you may deduce that eutrophication is occurring.
Derive – Manipulate mathematical relationships to obtain a new equation or value. For example, you may derive a percentage change from raw environmental data or rearrange an equation to calculate population density.
Design – Produce a plan or investigation. For example, if asked to design an investigation into water quality, you should identify the research question, variables, sampling method, equipment, data collection techniques, and methods for ensuring reliable results.
Determine – Find the only possible answer. For example, after analysing a biodiversity index, you may determine which study site has the greatest species diversity.
Discuss – Present a balanced argument considering different viewpoints. For example, if asked to discuss the use of nuclear energy, you should consider benefits such as low greenhouse gas emissions alongside disadvantages including radioactive waste, accident risks, and high construction costs.
Evaluate – Assess strengths, weaknesses, implications, and limitations. For example, if asked to evaluate the effectiveness of protected areas in conserving biodiversity, you should consider both their successes in protecting habitats and their limitations, such as funding challenges, habitat fragmentation, and enforcement issues.
Explain – Give detailed reasons or mechanisms. For example, if asked to explain how deforestation contributes to climate change, you would describe how removing forests reduces carbon sequestration while increasing carbon dioxide emissions through decomposition and burning.
Predict – Give an expected outcome based on evidence or knowledge. For example, if global temperatures continue to rise, you could predict increased sea-level rise, shifts in species distributions, more frequent extreme weather events, and reduced biodiversity in vulnerable ecosystems.
Show – Present all stages of a calculation or derivation. For example, if calculating the percentage increase in atmospheric carbon dioxide concentration, you should include each calculation step as well as the final answer.
Sketch – Draw a simple diagram showing the essential features. For example, you may sketch an energy pyramid showing producers at the base and successive consumer trophic levels above, without worrying about exact proportions.
Solve – Obtain the answer using mathematical methods. For example, you may solve a calculation involving population growth rate, energy efficiency, or percentage change using the data provided.
Suggest – Propose a reasonable explanation or hypothesis. For example, if biodiversity unexpectedly decreases at one sampling site, you might suggest that pollution, habitat disturbance, invasive species, or changes in land use are responsible.
We hope you found this post helpful! For more useful materials associated with the IB, check out the wide variety of IA, EE and TOK exemplars available at Clastify and other guides available on our blog.
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