Most IB ESS students know the content — but they still lose marks because they don't answer the way the examiner expects. The command term in every question tells you exactly what type of response is needed. Getting this wrong can cost you 2–4 marks per question.
This guide breaks down the six command terms that cause the most confusion, with side-by-side ESS examples so you can see exactly what a strong answer looks like.
Describe — Say WHAT happens
What it means: Give a detailed account of features, characteristics, or a process. No reasons needed — just state what you observe or what occurs.
ESS example question: "Describe the trend shown in the graph of global CO₂ concentrations from 1960 to 2020."
❌ Weak answer: "CO₂ has gone up because of burning fossil fuels."
This explains WHY — the question only asks you to describe the trend.
✅ Strong answer: "Global CO₂ concentrations have increased steadily from approximately 315 ppm in 1960 to over 415 ppm in 2020. The rate of increase has accelerated, with a seasonal fluctuation pattern visible each year."
States the trend, includes data, and mentions the pattern — all without explaining causes.
Explain — Say WHAT happens and WHY
What it means: Give a detailed account AND provide reasons or causes. You need to connect facts with reasoning using words like "because", "this leads to", "as a result".
ESS example question: "Explain why deforestation leads to increased soil erosion."
❌ Weak answer: "When trees are cut down, the soil gets washed away."
States the effect but doesn't explain the mechanism.
✅ Strong answer: "Tree roots bind soil particles together and increase soil stability. When trees are removed through deforestation, the root network is lost, leaving soil exposed. Without the canopy to intercept rainfall, raindrops hit the bare soil directly, dislodging particles. This leads to increased surface runoff, which carries the loosened topsoil downhill, accelerating erosion."
Chain of reasoning: cause → mechanism → effect. Each sentence links to the next.
Evaluate — Judge the value with evidence
What it means: Make a judgment about a strategy, solution, or argument by weighing strengths and limitations. You MUST reach a conclusion.
ESS example question: "Evaluate the effectiveness of recycling as a strategy for reducing solid domestic waste."
❌ Weak answer: "Recycling is good because it reduces waste in landfills. However, not everything can be recycled."
Too vague. No specific evidence and the conclusion is missing.
✅ Strong answer: "Recycling reduces the volume of waste sent to landfills and conserves raw materials — for example, recycling aluminium uses 95% less energy than producing new aluminium. However, recycling has limitations: contamination of recyclable materials often leads to rejection, and some materials like mixed plastics are difficult to recycle economically. In many developing countries, lack of infrastructure limits recycling rates to below 10%. Overall, recycling is effective as part of a broader waste management strategy but cannot solve the waste problem alone — it must be combined with reduction and reuse to be truly effective."
Strengths with evidence → limitations with evidence → balanced conclusion.
Discuss — Explore multiple perspectives
What it means: Present different viewpoints or arguments about an issue. Similar to evaluate, but focuses more on exploring the debate than reaching a single judgment.
ESS example question: "Discuss the use of genetically modified organisms (GMOs) in agriculture."
❌ Weak answer: "GMOs are bad because they harm the environment and are unnatural."
One-sided and no evidence. A "discuss" question requires multiple perspectives.
✅ Strong answer: "Proponents of GMOs argue they can increase crop yields, improve nutritional content (such as Golden Rice with added vitamin A), and reduce pesticide use through built-in pest resistance. However, critics raise concerns about biodiversity loss if GM crops cross-pollinate with wild species, the economic dependence of farmers on seed companies, and uncertainty about long-term ecological impacts. From an environmental perspective, the benefits depend on how GMOs are managed — in monoculture systems they may reduce biodiversity, while in targeted applications they could reduce chemical inputs."
Arguments for → arguments against → contextual nuance. Multiple stakeholder perspectives shown.
Analyse — Break it down
What it means: Break down information to identify patterns, relationships, or component parts. Go beyond describing — show how things connect.
ESS example question: "Analyse the data in the table showing species diversity in two different forest ecosystems."
❌ Weak answer: "Forest A has more species than Forest B."
This only describes the data. Analysis requires identifying patterns and explaining relationships.
✅ Strong answer: "Forest A has a Simpson's Diversity Index of 0.89 compared to 0.45 for Forest B, indicating significantly higher biodiversity. Forest A shows a more even distribution of species, with no single species dominating — the most abundant species represents only 12% of individuals. In contrast, Forest B is dominated by one species (68% of individuals), suggesting it may be a managed plantation or an early-succession ecosystem with low species evenness."
Uses data → identifies a pattern → interprets the relationship → suggests an explanation.
Distinguish — Show the differences
What it means: Make clear the differences between two or more concepts. Focus on what separates them, not their similarities.
ESS example question: "Distinguish between a food chain and a food web."
❌ Weak answer: "A food chain shows what eats what. A food web is bigger."
Vague. Does not clearly state how they differ.
✅ Strong answer: "A food chain is a single linear pathway showing the transfer of energy from one trophic level to the next (e.g., grass → rabbit → fox). A food web, in contrast, represents multiple interconnected food chains within an ecosystem, showing that most organisms feed on more than one species and can occupy more than one trophic level."
Defines each concept clearly, then highlights the specific difference with an example.
Quick reference table
| Command term | What to do | Key signal words |
|---|---|---|
| Describe | State what happens — no reasons | what, how (process), the trend shows |
| Explain | State what happens AND give reasons | because, this leads to, as a result |
| Evaluate | Weigh strengths and limitations → conclude | however, on balance, overall |
| Discuss | Present multiple perspectives | proponents argue, critics suggest, from the perspective of |
| Analyse | Break down, find patterns and relationships | the data shows, this suggests, the pattern indicates |
| Distinguish | Clearly state the differences | in contrast, whereas, unlike |
The mistakes that cost the most marks
- Describing when asked to explain — Always ask yourself: "Have I said WHY?" If not, you're only describing.
- One-sided evaluations — Evaluate and discuss questions require at least two perspectives. A one-sided answer cannot earn top marks.
- Forgetting the conclusion — Evaluate questions need a final judgment. Without it, you've only listed pros and cons.
- Listing facts instead of analysing — Analysis means showing how facts connect, not just stating them.
Want to see the full list of all 23 IB command terms? Check our complete IB command terms reference.
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