IB Biology command terms are the instructional verbs in exam questions, such as state, outline, explain, and evaluate. They tell you what intellectual task to perform and how much depth your response requires. Knowing the biology is not enough if your answer does not perform the task specified by the command term.
The current IB Biology guide, for first assessment in 2025, organizes command terms broadly by assessment objective. Some require concise recall, others require application, and the most demanding require analysis, evaluation, or synthesis. The definitions below follow the current guide, while the response strategies are practical advice rather than fixed IB rules.
Why IB Biology command terms matter
A command term determines what can earn credit. If a question says state, adding a lengthy mechanism wastes time. If it says explain, merely naming the outcome is incomplete because the answer needs reasons, causes, or a mechanism.
Always read three parts of a question before writing:
- Command term: What must you do?
- Biological content: What topic must you address?
- Scope and context: Does the question specify an organism, data set, condition, or number of examples?
The mark allocation can help you judge breadth, but there is no universal rule that one mark always equals one sentence. A concise sentence may contain several relevant ideas, while a long sentence may contain none. Treat the available marks as a guide to the number of distinct, developed points required.
Essential recall and representation terms
These terms commonly ask for precise knowledge or a correctly presented visual response.
| Command term | What the IB expects | Biology example and suitable response |
|---|---|---|
| Define | Give the precise meaning of a word, phrase, concept, or physical quantity. | Define an allele. An allele is one of two or more alternative forms of a gene. |
| State | Give a specific name, value, or brief answer without explanation or calculation. | State the site of translation. Ribosomes. |
| List | Give a sequence of brief answers with no explanation. | List three components of a nucleotide. Phosphate group, pentose sugar, nitrogenous base. |
| Identify | Provide an answer from several possibilities. | Identify the organelle shown. Mitochondrion. |
| Label | Add labels to a diagram. | Place accurate names beside the appropriate structures, using clear label lines. |
| Draw | Produce a labelled, accurate diagram or graph using a pencil. | A cell drawing should use clear lines, accurate proportions, labels, and a ruler for straight lines. |
| Measure | Obtain a value for a quantity. | Read the specimen length from a scale and include the appropriate unit. |
A definition is not the same as an example. Defining osmosis by saying “water entering a plant cell” gives an instance, but not its precise meaning. A complete definition must establish the net movement of water through a selectively permeable membrane down a water-potential gradient.
Application and detailed-account terms
These terms require more than recalling an isolated fact. You may need to apply knowledge, report detail, distinguish concepts, or summarize a process.
| Command term | Required depth | Effective approach |
|---|---|---|
| Annotate | Add brief notes to a diagram or graph. | Combine labels with short functional or explanatory notes. |
| Apply | Use an idea, equation, principle, theory, or law in relation to a problem. | Select relevant biological knowledge and use it in the unfamiliar context provided. |
| Calculate | Obtain a numerical answer while showing relevant working stages. | Write the formula, substitute values, calculate, and give units where applicable. |
| Describe | Give a detailed account. | Report what happens, what is present, or what pattern the data show. Include sequence and values where relevant. |
| Distinguish | Make differences between two or more items clear. | Use paired contrasts such as “X does..., whereas Y does....” |
| Estimate | Obtain an approximate value. | Read or infer a reasonable value and show how it was obtained when useful. |
| Outline | Give a brief account or summary. | Include the principal stages or features without developing every mechanism. |
Outline, describe, and explain compared
These three terms often cause avoidable errors. Consider a question about ventilation:
- Outline ventilation: Air moves into the lungs during inhalation and out during exhalation.
- Describe inhalation: The diaphragm contracts and flattens, the external intercostal muscles contract, the rib cage moves up and out, and thoracic volume increases.
- Explain inhalation: Contraction of the diaphragm and external intercostal muscles increases thoracic volume. This lowers pressure inside the lungs below atmospheric pressure, so air moves into the lungs down the pressure gradient.
An outline selects the main features. A description supplies a detailed account of what occurs. An explanation establishes why or how it occurs through connected causal reasoning.
Higher-order analytical command terms
These terms often appear in data-based, experimental, and extended-response questions. They require conclusions, relationships, evidence, or judgments rather than unconnected factual recall.
| Command term | What a successful answer does |
|---|---|
| Analyse | Breaks information down to reveal essential elements, patterns, or relationships. |
| Comment | Gives a judgment based on a statement or calculated result. |
| Compare | Gives similarities between items, referring to both throughout. |
| Compare and contrast | Gives both similarities and differences, referring to all items throughout. |
| Construct | Displays information in a diagrammatic or logical form. |
| Deduce | Reaches a conclusion from information supplied in the question. |
| Design | Produces a plan, simulation, or model. |
| Determine | Obtains the only possible answer. |
| Discuss | Offers a considered, balanced review of arguments, factors, or hypotheses, supported by evidence. |
| Evaluate | Makes an appraisal by weighing strengths and limitations. |
| Explain | Gives a detailed account including reasons or causes. |
| Justify | Provides valid reasons or evidence supporting an answer or conclusion. |
| Predict | Gives an expected result. |
| Sketch | Shows the general shape or relationship in a diagram or graph, including relevant features. |
| Suggest | Proposes a possible solution, hypothesis, or answer. |
A frequently misunderstood point is that the current Biology guide defines compare in terms of similarities. If the question says compare and contrast, both similarities and differences are needed. In either case, write paired points that refer explicitly to both items rather than completing two disconnected mini-essays.
Explain, discuss, and evaluate compared
Suppose a question concerns biological control of an invasive species:
- Explain asks for the mechanism, such as how a predator reduces the invasive population and changes competition.
- Discuss asks for a balanced review of relevant factors, potentially including effectiveness, effects on non-target organisms, ecological uncertainty, and alternatives.
- Evaluate asks you to appraise the approach by weighing strengths against limitations and reaching a supported judgment.
An evaluation should not be a generic list of advantages and disadvantages. State the criteria being used, connect each judgment to evidence or biological reasoning, and finish with a qualified conclusion. For example, biological control may be effective and require little repeated application, but it is difficult to reverse and may threaten non-target species, so its suitability depends on rigorous host-specificity testing.
Command terms in data-based questions
Data questions test both reading accuracy and biological interpretation. Match your response to the verb:
- Describe: Quote the overall trend, relevant values, maxima or minima, and anomalies. Do not explain the mechanism unless asked.
- Analyse: Break the data into meaningful patterns, compare conditions, and identify relationships supported by values.
- Calculate: Show working and retain appropriate units.
- Deduce: Derive a conclusion from the supplied evidence rather than simply recalling a textbook fact.
- Suggest: Offer a biologically plausible answer. More than one response may be defensible, but it must fit the evidence.
- Evaluate: Consider reliability, uncertainty, sample size, controls, variation, and whether the evidence supports the stated conclusion.
If instructed to use the data, numerical evidence matters. “Enzyme activity increased” is less informative than “activity increased from 12 to 29 arbitrary units between 20°C and 40°C.” Do not claim causation merely because two variables are correlated.
Common command-term mistakes
- Explaining when asked to state: This consumes time without answering additional demands.
- Describing when asked to explain: Reporting that enzyme activity falls does not explain denaturation or changes to the active site.
- Giving examples instead of definitions: Examples illustrate meaning but rarely establish it precisely.
- Writing separate accounts for comparisons: Use linked sentences containing both items.
- Treating discuss and evaluate as synonyms: Discussion reviews a range of arguments or factors; evaluation explicitly appraises strengths and limitations.
- Ignoring the question context: A correct explanation about respiration may still be irrelevant if the question asks specifically about anaerobic respiration in yeast.
- Forgetting evidence: Judgments and conclusions should be supported by data or biological reasoning.
How to internalise command terms efficiently
Memorizing definitions is useful, but the fastest route to reliable exam technique is seeing many questions worked through. You need to observe how a short state response differs from a causal explain response and how an evaluate answer weighs evidence before reaching a judgment.
Use this practice cycle:
- Circle the command term and underline the biological scope.
- Translate the term into a task, such as “give causes” or “weigh strengths and limitations.”
- Plan distinct points using the mark allocation as a guide.
- Answer without unnecessary background information.
- Compare your response with the markscheme or worked solution.
- Rewrite the answer, correcting both content and command-term depth.
The IB Biology Questionbank allows targeted exam-style practice, while the Biology video library helps you watch questions and concepts worked through. Use the available per-question video explanations and worked solutions to notice exactly how each response matches its command term. Jojo AI can then identify when an answer contains correct biology but lacks the required reasoning, comparison, or judgment.
For knowledge gaps revealed by practice, return to the IB Biology resource hub or use Biology flashcards to strengthen precise definitions. Once individual terms feel secure, complete Biology predicted papers under timed conditions to practise switching between different response depths.
Conclusion
IB Biology command terms tell you both what to do and how deeply to do it. State and list require brevity, describe requires detail, explain requires causal reasoning, and discuss or evaluate requires supported higher-order judgment. Read the command term alongside the question scope and mark allocation, then provide only the type of response requested.
Repeated exam-question practice is more effective than memorizing a glossary alone. RevisionDojo’s Biology Questionbank, per-question video solutions, and Jojo AI feedback can help you connect each official definition to the form of answer that earns credit.
Sources and referenced URLs
- Official IB Biology programme page
- IB Biology guide for first assessment 2025
- Official IB Biology specimen papers
- IB assessment principles and practices
- RevisionDojo guide to IB Biology command terms
- RevisionDojo IB Biology Questionbank
- RevisionDojo Biology video library
- RevisionDojo IB Biology resource hub
- RevisionDojo Biology flashcards
- RevisionDojo Biology predicted papers