Decoding the ESS SL command-term matrix: from Paper 1 to Paper 2
A working map of IB ESS SL command terms, showing which rubric criterion each verb triggers on Paper 1 and Paper 2 and how to turn marks into a 7.
IB Environmental Systems and Societies is unusual inside the IB Diploma because it is the only SL-only science that lets arts-track candidates sit a Group 4 subject. That single fact reshapes how command terms behave. Most ESS SL candidates reading this are juggling Language and Literature, History or Geography at the same time, and the verbs that appear at the top of a Paper 2 8-marker often feel borrowed from another subject. They aren't. Each command term is wired to a specific rubric criterion, and recognising the wiring is the difference between a band 5 answer and a band 7 answer that looks similar on the page.
This guide builds a working map of the eight or nine command terms that really decide your grade on ESS SL Paper 1 and Paper 2, shows which assessment objective each one triggers, and gives concrete answering moves for the ones that trip candidates most often. Read it once before you start a topic, again before each mock, and once more the week of the exam.
Why command terms matter more in ESS than in most Group 4 subjects
Biology, Chemistry and Physics share a Group 4 mark scheme, so a verb like "evaluate" pulls the same rubric criteria in all three. ESS borrows verbs from Group 4 and from the humanities, and the IB mark-scheme writers have mapped them to two separate assessment objectives: Knowledge and Understanding (criterion A) and Analysis, Evaluation and Synthesis (criterion B). A 6-mark answer on Topic 4 is rarely a "describe" — it is almost always an "evaluate" or "discuss" — and the verbs decide which criterion the examiner is actually scoring you on.
In practice, a candidate who writes a beautifully structured "describe" answer to an "evaluate" question will lose 2 to 3 marks because the response shows no judgement, even if the content is accurate. Most candidates reading this underestimate how literal the rubric is. Treat the command term as a contract.
The two assessment objectives ESS SL examiners score against
Before mapping verbs, you need to know the two criteria that absorb almost all the marks on Papers 1 and 2:
- Criterion A — Knowledge and Understanding. Marks for accurate, relevant science content: definitions, named processes, units, and the use of environmental systems terminology in context.
- Criterion B — Synthesis, Evaluation and Research Skills. Marks for the reasoning moves: comparing perspectives, weighing evidence, drawing conclusions and proposing justified actions.
On Paper 1 short answers, criterion A typically dominates. On Paper 2 Section A data-response and Section B 8-markers, criterion B carries the larger share. The command term at the start of the question tells you which side to lean on.
Eight command terms that decide your ESS SL grade
The list below is ordered from the verb most candidates over-perform on to the verb that costs the most marks in real marking sessions. For each, I have noted which criterion it primarily triggers and a one-line tactical answer frame.
Define and State
Both verbs are pure criterion A. "Define" expects a textbook-quality sentence (for example: "Eutrophication is the enrichment of a water body with nutrients, typically nitrates and phosphates, leading to excessive algal growth"). "State" is a one-clause recall. In ESS SL, these appear inside Section A of Paper 1 as 1-markers. Most candidates reading this over-write and burn 90 seconds they will need for an 8-marker later.
Describe
Still criterion A, but with a structural requirement: trend, mechanism, and a concrete example. For Topic 5 atmospheric systems, a "describe" answer that names ozone depletion, references CFCs and gives the Antarctic springtime maximum will earn full marks. A description that ignores one of those three legs is capped at 2 of 3 marks.
Explain
The transition verb. It pulls on criterion A for the science and on criterion B for the causal chain. A solid 3-mark "explain" is two sentences: the first names the mechanism, the second links cause to effect with a "because" or "which results in". Candidates who write three paragraphs of background lose the thread.
Distinguish and Compare
This pair catches out the strongest students. "Distinguish between X and Y" is criterion A: list two parallel differences, no judgement required. "Compare" is criterion B: you must explicitly say how X and Y differ or are similar, not just list them. Most ESS SL answers under-mark on "compare" because they write two parallel definitions with no comparative sentence. Add one sentence that says "Unlike X, Y…" or "Both X and Y…, however X…" and the mark lifts immediately.
Discuss
The single most common Paper 2 Section B opener. "Discuss" is a balanced criterion B verb: it expects at least two perspectives on the same environmental issue, evidence for each, and a justified conclusion. A 6-mark "discuss" needs roughly 220 to 280 words and at least one named stakeholder perspective (e.g. smallholder farmer, government policy, indigenous community). Without a stakeholder, the answer is capped at 3 of 6.
Evaluate
The hardest verb on the mark scheme. "Evaluate" asks for a judgement against a criterion, not a list. A 4-mark "evaluate" of a named management strategy needs: the strategy named, two strengths, two limitations, and a final sentence that says which side wins and why. Candidates who write "in conclusion, both sides have valid points" lose the last 1 to 2 marks. Pick a side and defend it with one piece of evidence.
To what extent and Justify
These are the verdict verbs. They appear in Topic 7 sustainability questions and on Paper 2 Section B. A "to what extent" answer needs a clear position in the first sentence, two arguments in favour, one argument against, and a closing sentence that restates the position with a qualifier ("largely", "only partially", "in the short term"). 4 of 5 candidates skip the qualifier and lose the band.
Command term to criterion: a one-glance map
Use the table below as a quick reference during revision. It is the same matrix IB examiners use to allocate marks, reduced to the verbs that actually appear in Paper 1 and Paper 2.
| Command term | Primary criterion | Typical paper | Marks | Move that costs the most marks |
|---|---|---|---|---|
| Define / State | A | Paper 1 Section A | 1 | Over-writing beyond 2 sentences |
| Describe | A | Paper 1 Section A | 2–3 | Missing the example leg |
| Explain | A → B | Paper 1 Section A | 2–3 | No explicit cause-to-effect link |
| Distinguish | A | Paper 1 Section A | 2 | Adding a judgement (unnecessary) |
| Compare | B | Paper 2 Section A | 3–4 | No comparative sentence |
| Discuss | B | Paper 2 Section B | 6 | No stakeholder perspective |
| Evaluate | B | Paper 2 Section B | 4 | Refusing to pick a side |
| To what extent / Justify | B | Paper 2 Section B | 4–6 | Missing the qualifying adverb |
Common pitfalls and how to avoid them
Three patterns cost ESS SL candidates the most marks each exam session, and all three are command-term mistakes in disguise.
- Treating "distinguish" as "compare". A "distinguish" answer that opens with "On the one hand…" is signalling a 2-mark answer where a 3-mark answer is available. Re-read the verb; if it is "distinguish", use bullet-style parallel sentences.
- Writing a "describe" when the question says "evaluate". The 8-marker on Topic 2 ecosystem structure is a common site. Candidates describe the carbon cycle in three paragraphs and have no room for the judgement. Cap yourself at 120 words of description, then move to evaluation.
- Skipping the qualifier on "to what extent". A flat "yes" or "no" verdict without "largely", "only partially" or "in the short term" reads as binary and caps the answer at band 5.
A 30-minute drill to lock the matrix in your head
Take any past Paper 2 Section B, cover the command term, and try to answer the question as if the verb were "describe". Then re-write the same question as "evaluate". Compare word counts. In my experience this usually reveals that the "evaluate" answer is only 60 to 80 words longer than the "describe" answer, but it picks up 2 to 3 extra marks because the rubric is criterion-B heavy. Repeat for "discuss" versus "to what extent" — the latter is a tighter structure and is the verb to prefer when the choice allows it.
What this means for your revision plan
Treat the command-term matrix as a second syllabus. Build a 12-week block where weeks 1 to 8 are topic content and weeks 9 to 12 are verb-specific drills. In week 9, answer four "evaluate" questions across different topics. In week 10, answer four "discuss" questions. By week 12 you should be able to glance at any verb and produce the right structure before reading the stimulus. That reflex is what moves a candidate from a 5 to a 6 or 7 in ESS SL, far more than memorising one extra topic.
Working with a tutor who has marked ESS SL papers is the fastest way to internalise this map. IB Courses' one-to-one ESS SL programme drills each command term against the rubric criterion it triggers and builds the answering reflex before the exam window opens.