13 Aug IB ESS Short Answers: Command Terms and Practice Examples
Good ESS short answers respond to the question, use accurate knowledge and include relevant evidence. The command term and mark allocation help you judge depth, but one sentence does not automatically equal one mark. These practice examples are illustrative learning aids, not official IB questions or verified full-mark answers.
Read the task before choosing a structure
Identify the command term, what the question refers to and any figures or units you need. A definition, calculation and explanation require different kinds of response. You do not need a named case study or numerical value in every answer; include one when the task needs it.
- State or identify: Give the requested fact or item directly.
- Define: Give the precise meaning of the term.
- Outline: Give a brief account or summary, rather than assuming it always means a list.
- Explain: Give reasons or show how a process leads to an outcome.
- Suggest: Offer a plausible response suited to the context.
- Calculate: Show relevant working, include units where applicable and use appropriate precision.
For official practice, use the correct syllabus, SL or HL paper and its question-specific markscheme. Assessment objectives are not separate automatic marks assigned to successive sentences.
Use flexible planning prompts
Ask: “What does the question require?”, “What evidence is relevant?” and “Have I explained the link?” Avoid compulsory word counts or sentence counts for one-, two- or three-mark responses. Repetition and unrelated detail rarely help, but a calculation may earn method credit without resembling a list of facts.
Four practice examples
1. Biodiversity
Practice task: Outline two possible consequences of reduced species diversity in a grassland.
Illustrative response: Loss of species can reduce the range of responses to environmental change, making some ecosystem functions less resilient. The loss of particular plant species can also reduce food or habitat for organisms that depend on them.
Review: Two possible consequences are identified with brief detail. Their occurrence depends on which species and functions are lost; avoid claiming that every decrease in richness causes the same outcome.
2. Eutrophication
Practice task: Explain how nutrient enrichment can reduce dissolved oxygen in a lake.
Illustrative response: Additional nutrients can stimulate algal growth. When increased organic material dies, aerobic decomposers respire while breaking it down, consuming dissolved oxygen. If oxygen demand exceeds replenishment, hypoxic conditions can harm oxygen-dependent organisms.
Review: The response links enrichment, organic matter and oxygen consumption. It should be adapted to any data or context in the actual question.
3. Trophic efficiency
Practice task: Define trophic transfer efficiency and suggest why it is below 100%.
Illustrative response: Trophic transfer efficiency is the percentage of production transferred from one trophic level into production at the next over a comparable period. Not all biomass is eaten or assimilated, and some assimilated energy is used in respiration and dissipated as heat.
Review: The definition and explanation are both present. A fixed 10% value is not a universal rule for every food web.
4. Data interpretation
Fictional practice data: Annual CO₂ emissions for a hypothetical region rise from 100 Mt CO₂ in 2000 to 140 Mt CO₂ in 2020. These values are invented for practice and are not a global emissions dataset.
Practice task: State the overall change and suggest one possible reason.
Illustrative response: Annual emissions increased by 40 Mt CO₂, or 40%, between the stated years. Increased fossil-fuel use is one possible explanation, but the two values alone do not establish the cause or show changes within the period.
Practise timing for your level
For the ESS course first assessed in 2026, Paper 2 Section A carries 40 marks at both levels. Plan practice using the full paper’s SL or HL duration and question choices. A minute-per-mark target can be a trial strategy, not an official or universally suitable limit. Reading, calculations and unfamiliar resources may need different amounts of time.
After a timed attempt, check the relevant markscheme and record one specific gap: knowledge, interpretation, units, explanation or pacing. Reattempt a related question to see whether the difficulty has changed.
Keep practice, CAS and assessed writing distinct
Practising ESS answers is academic study and does not automatically count as CAS. A separate environmental activity may offer CAS opportunities, subject to the school’s approval and rules; do not double-count assessed coursework as CAS.
Concise explanation can help your IA, but exam models are not text to transplant into an assessed report. Use your own evidence and reasoning, acknowledge sources and follow your school’s rules about assistance. Paraphrasing a model or replacing its numbers does not automatically make it independent work.
Discuss your practice answers
Marija Maletz has 13 years of teaching experience and more than 10 years as an IB ESS examiner. Regular lessons can focus on understanding a concept, interpreting a resource or developing a response to a command term.
Request a FREE 20-minute trial lesson to discuss your level, main difficulty and a starting point. The introduction does not promise a fully marked paper or detailed IA review.
Official reference
IB ESS guide, first assessment 2026. Use school-authorised practice papers and their markschemes for formal exam preparation.
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