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Exam skills

IB Biology command terms

The first word of an exam question tells you what kind of answer earns the marks. Here are all 28 command terms in the IB Biology guide: what each one wants, the traps, and an example with a model answer.

28 command terms3 assessment objectives

Three rules that hold for every question

  1. The command term sets the depth. "State" wants a word; "Explain" wants the reason behind it. Answering the wrong one costs marks even when your biology is right.
  2. The marks tell you how many points. A [3] needs three separate, creditable points. On longer answers, add one spare.
  3. Read the words around the term. "Using all the data", "one" and "two" change what earns marks (see below).

From short to deep

The same topic, asked with five terms. Each step adds something the one before it does not need.

Statethe fact
Outlinethe main points, briefly
Describethe full account of what happens
Explainplus why: the cause of each step
Discuss · Evaluateplus both sides and a judgement

All 28 command terms

Grouped by assessment objective (AO), as in the IB Biology guide. Find a term, or jump to it.

AO1DefineDrawLabelListMeasureState
AO2AnnotateCalculateDescribeDistinguishEstimateIdentifyOutline
AO3AnalyseCommentCompareCompare and contrastConstructDeduceDesignDetermineDiscussEvaluateExplainJustifyPredictSketchSuggest

AO1: Recall

Short answers that show you know the fact. No reasons, no working.

Define

AO1 · Recall

Give the exact meaning of a word, phrase or concept.

Earns marks
The precise meaning, including its key qualifying words. Usually 1 mark.
Watch out
An example is not a definition. Learn the small words that carry the mark, such as net, partially permeable or heritable.
In exams
Rare (under 1% of parts), 1 mark.
Example question and model answer

Define osmosis. [1]

  • the net movement of water molecules across a partially permeable membrane, from a lower to a higher solute concentration;

Often confused with State, Outline.

Draw

AO1 · Recall

Make an accurate, labelled diagram or graph in pencil: a ruler for straight lines, drawn to scale, points plotted exactly and joined with a straight line or smooth curve.

Earns marks
Correct shape and proportions, plus every label the question needs. Marks often go to the labels.
Watch out
No shading or sketchy double lines. Label lines must touch the structure. Graphs need both axes labelled with units.
In exams
About 2% of parts, 1 to 4 marks (Punnett grids, molecules, cell structures).
Example question and model answer

Draw a labelled diagram of a section through a phospholipid bilayer. [3]

  • two layers of phospholipids, tails facing inwards;
  • heads labelled hydrophilic (phosphate) heads;
  • tails labelled hydrophobic (hydrocarbon/fatty acid) tails;
  • at least one layer drawn with heads touching each other in a continuous row;

Often confused with Sketch, Construct.

Label

AO1 · Recall

Add the names of parts to a diagram.

Earns marks
One correct name per mark, on a line that clearly points to the right part.
Watch out
Names only: no notes on function (that is Annotate). A label line that stops short or points between two parts loses the mark.
In exams
Not seen in recent papers, but on the list.
Example question and model answer

A diagram of a bacterium is shown. Label the nucleoid and one ribosome. [2]

  • nucleoid: a line to the region of coiled DNA, with no membrane around it;
  • ribosome: a line to one of the small dots in the cytoplasm;

Often confused with Annotate, Identify.

List

AO1 · Recall

Give a series of brief answers, with no explanation.

Earns marks
One brief item per point asked for.
Watch out
Give only as many as asked. Extra items gain nothing, and a wrong one can cancel a right one.
In exams
Rare (under 1% of parts), 1 mark.
Example question and model answer

List two products of the light-dependent reactions that are used in the Calvin cycle. [1]

  • ATP and reduced NADP (both needed for the mark);

Often confused with State, Outline.

Measure

AO1 · Recall

Find the value of a quantity, for example with a ruler or by reading a scale.

Earns marks
A value in the accepted range, with its unit.
Watch out
Always give the unit. On a micrograph, measure the image, then use the scale bar or magnification to get the real size.
In exams
Not seen in recent papers, but on the list.
Example question and model answer

On a micrograph, a 10 μm scale bar is 20 mm long. Measure the real length of the guard cell, which is 48 mm long on the image. [1]

  • 24 μm (48 ÷ 20 × 10), unit included;

Often confused with Calculate, Estimate.

State

AO1 · Recall

Give a name, a value or another short answer, with no explanation or working.

Earns marks
The fact itself. Almost always 1 mark.
Watch out
A word or phrase is enough. Adding reasons wastes time, and a wrong extra detail can lose the mark.
In exams
About 13% of parts; nearly always 1 mark.
Example question and model answer

State the type of bond that links adjacent nucleotides in one strand of DNA. [1]

  • phosphodiester bond / covalent bond;
  • (hydrogen bonds hold the two strands together, so they score nothing here)

Often confused with Define, Identify, List.

AO2: Apply

Accounts, working and comparisons: more detail, but still no judgement.

Annotate

AO2 · Apply

Add brief notes to a diagram or graph: a label plus what it means or does.

Earns marks
Each note must say something about the feature, not just name it.
Watch out
A bare label is not an annotation. Keep each note short and next to the feature it describes.
In exams
Rare (under 1% of parts), 1 mark.
Example question and model answer

On a graph of enzyme activity against temperature, annotate the peak and the steep fall after it. [2]

  • peak: optimum temperature, where enzyme-substrate collisions are most frequent and successful;
  • fall: active site changes shape (denaturation), so substrate no longer fits;

Often confused with Label, Describe.

Calculate

AO2 · Apply

Work out a numerical answer, showing the steps of the working.

Earns marks
The correct answer with its unit. Working can earn credit even if the final answer is wrong.
Watch out
Write the substitution, not just the result. Give the unit and a sensible number of significant figures.
In exams
About 4% of parts; usually 1 mark, sometimes 2. Units are usually required.
Example question and model answer

In a capture-mark-release-recapture study, 40 woodlice were marked and released. Later, 50 were caught, of which 10 were marked. Calculate the estimated population size. [1]

  • (40 × 50) ÷ 10 = 200 woodlice;

Often confused with Estimate, Determine, Measure.

Describe

AO2 · Apply

Give a detailed account of what is there or what happens. For data: the trend, any change in the trend, and values.

Earns marks
One mark per accurate detail. For data, quote values with units.
Watch out
No reasons: why something happens belongs to Explain. For a graph, give the overall trend, then where it changes, then numbers.
In exams
About 10% of parts, usually 2 or 4 marks (often 'Describe the trend' or 'Describe the relationship').
Example question and model answer

A graph shows the rate of photosynthesis at light intensities from 0 to 600 units. Describe the relationship between light intensity and the rate of photosynthesis. [2]

  • the rate increases as light intensity increases, up to about 400 units;
  • above about 400 units the rate stays constant / levels off (at about 12 units);

Often confused with Outline, Explain.

Distinguish

AO2 · Apply

Make clear the differences between two or more things.

Earns marks
One mark per difference, and each difference must mention both things.
Watch out
Write each point as a pair: 'X ..., whereas Y ...'. Separate facts about each item (a list for X, then a list for Y) usually score nothing.
In exams
About 6% of parts, usually 2 marks.
Example question and model answer

Distinguish between DNA and RNA. [2]

  • DNA contains deoxyribose, whereas RNA contains ribose;
  • DNA contains thymine, whereas RNA contains uracil;
  • DNA is usually double-stranded, whereas RNA is usually single-stranded;
  • (any two)

Often confused with Compare and contrast, Compare.

Estimate

AO2 · Apply

Find an approximate value.

Earns marks
A value inside the accepted range, with its unit.
Watch out
Approximate does not mean a wild guess: show how you got it, and give the unit.
In exams
Under 1% of parts, 1 mark.
Example question and model answer

Ten 0.25 m² quadrats held a mean of 4.8 daisies each. Estimate the number of daisies on a 50 m² lawn. [1]

  • about 960 daisies (4.8 ÷ 0.25 = 19.2 per m²; × 50); accept 900 to 1000;

Often confused with Calculate, Measure.

Identify

AO2 · Apply

Pick out the answer from a number of possibilities: a graph, table, diagram or list.

Earns marks
The right answer, usually 1 mark.
Watch out
Do not explain. If the question says one, give one: a second, wrong answer can cancel the right one.
In exams
About 9% of parts, usually 1 mark.
Example question and model answer

In the food chain grass → grasshopper → frog → snake, identify the trophic level of the snake. [1]

  • tertiary consumer / fourth trophic level;

Often confused with State, Deduce.

Outline

AO2 · Apply

Give a brief account or summary: the main points, in order if it is a process.

Earns marks
One creditable point per mark. No reasons needed.
Watch out
Brief, but not too brief: a 4-mark Outline needs four separate points. The commonest term on the papers.
In exams
About 17% of parts, the most common term; 1 to 4 marks.
Example question and model answer

Outline the process of transcription. [4]

  • RNA polymerase binds to the promoter;
  • the DNA strands separate / the double helix unwinds;
  • free RNA nucleotides pair with complementary bases on the template strand (uracil pairs with adenine);
  • RNA polymerase joins the nucleotides, building mRNA in the 5′ to 3′ direction;
  • the mRNA separates from the DNA, which rewinds;

Often confused with Describe, State.

AO3: Analyse, evaluate, create

Reasons, conclusions, judgements and plans: the highest-mark terms.

Analyse

AO3 · Analyse, evaluate, create

Break information down to bring out its key parts, patterns or relationships.

Earns marks
Each pattern found, supported by values, and what it shows.
Watch out
Do not just restate the data. Compare the conditions, quote numbers, and say what each pattern means.
In exams
Under 1% of parts, 2 to 3 marks.
Example question and model answer

Discs soaked in an antibiotic were placed on two bacterial strains. Clear zones were 18 mm (strain A) and 2 mm (strain B) at the low dose, and 26 mm and 3 mm at the high dose. Analyse the data. [3]

  • strain A is sensitive: large clear zones;
  • strain A's clear zone increases with dose (18 to 26 mm), so more bacteria are killed;
  • strain B is resistant: almost no clear zone at either dose;
  • so a higher dose would not treat an infection caused by strain B;

Often confused with Evaluate, Deduce, Describe.

Comment

AO3 · Analyse, evaluate, create

Give a judgement on a given statement or on the result of a calculation.

Earns marks
A clear judgement plus the reason for it.
Watch out
Do not just repeat the statement. Say whether it holds (or how far), and why.
In exams
Seen inside longer instructions rather than as an opening word.
Example question and model answer

A student counted 25 cells in an onion root tip and calculated a mitotic index of 0.12. Comment on the reliability of this result. [2]

  • the result is not very reliable;
  • 25 cells is a small sample / one field of view may not be representative;
  • counting more cells in several fields of view would improve it;

Often confused with Evaluate, Discuss.

Compare

AO3 · Analyse, evaluate, create

Give an account of the similarities between two or more items, referring to all of them throughout.

Earns marks
One mark per similarity that applies to both items.
Watch out
In the IB definition, Compare means similarities. Differences are asked for with 'Compare and contrast' or 'Distinguish'. Write 'both ...'.
In exams
Used on its own very rarely (1 of 291 parts); 'Compare and contrast' is far more common.
Example question and model answer

Compare the light-dependent reactions of photosynthesis with the electron transport chain in cell respiration. [2]

  • both pass electrons along a chain of carriers in a membrane;
  • both use the energy to pump protons, making a proton gradient;
  • both make ATP by chemiosmosis through ATP synthase;

Often confused with Compare and contrast, Distinguish.

Compare and contrast

AO3 · Analyse, evaluate, create

Give an account of the similarities and the differences between two or more items, referring to all of them throughout.

Earns marks
Points for similarities and points for differences. Full marks usually need at least one of each.
Watch out
Write linked points about both items, not two separate descriptions. Do not leave out the similarity.
In exams
About 4% of parts, usually 2 or 3 marks, almost always on data.
Example question and model answer

Compare and contrast mitosis and meiosis. [3]

  • similarity: both are preceded by DNA replication / both use a spindle to move chromosomes;
  • mitosis has one division, whereas meiosis has two;
  • mitosis produces genetically identical diploid cells, whereas meiosis produces genetically different haploid cells;
  • crossing over happens in meiosis but not in mitosis;

Often confused with Compare, Distinguish.

Construct

AO3 · Analyse, evaluate, create

Show information in a diagram or a logical form, such as a table, key, Punnett grid, food web or cladogram.

Earns marks
The correct form, set out with its conventions, plus correct content.
Watch out
Follow the conventions: gametes on the edges of a Punnett grid, headings and units in a table, branches in the right order in a cladogram.
In exams
Seen inside longer instructions (for example, constructing a Punnett grid).
Example question and model answer

Two parents are both carriers of cystic fibrosis (Ff). Construct a Punnett grid to show the possible genotypes of their children. [2]

  • gametes F and f shown for each parent on the edges of the grid;
  • offspring FF, Ff, Ff and ff in the grid (1 in 4 chance of cystic fibrosis);

Often confused with Draw, Design.

Deduce

AO3 · Analyse, evaluate, create

Reach a conclusion from the information given.

Earns marks
The conclusion, and the step of reasoning that leads to it from the evidence.
Watch out
The answer must follow from the information on the page (a pedigree, a cross, a data table), not from memory. Show the evidence you used.
In exams
About 3% of parts, 1 to 3 marks; often pedigrees and crosses.
Example question and model answer

Two unaffected parents have a daughter with a genetic condition. Deduce how the condition is inherited, giving a reason. [2]

  • recessive, because neither parent is affected, so both must be carriers;
  • autosomal, because if it were X-linked recessive, an affected daughter would need an affected father;

Often confused with Predict, Suggest, Determine.

Design

AO3 · Analyse, evaluate, create

Produce a plan, simulation or model.

Earns marks
For an experiment: the variable changed and how, what is measured and how, the variables kept constant, repeats, and how results are recorded.
Watch out
Be specific enough that someone else could carry it out: give real values and real equipment.
In exams
Not seen as an opening word recently, but on the list (also central to the internal assessment).
Example question and model answer

Design an experiment to find the effect of temperature on the activity of catalase. [4]

  • vary temperature: at least five values, e.g. 10 to 50 °C, using water baths;
  • measure the volume of oxygen released per minute, with a gas syringe or by counting bubbles;
  • keep constant: pH (buffer), enzyme concentration, and the concentration and volume of hydrogen peroxide;
  • let both solutions reach the temperature before mixing;
  • repeat at least three times at each temperature and calculate a mean;

Often confused with Construct, Suggest.

Determine

AO3 · Analyse, evaluate, create

Find the only possible answer.

Earns marks
The single correct answer, often a number or genotype.
Watch out
There is one right answer: show how you got it, and do not give alternatives.
In exams
Not seen as an opening word recently, but on the list.
Example question and model answer

A diploid body cell of a dog has 78 chromosomes. Determine the number of chromosomes in a dog sperm cell. [1]

  • 39 (meiosis halves the number);

Often confused with Calculate, Deduce.

Discuss

AO3 · Analyse, evaluate, create

Give a considered, balanced review of a range of arguments, factors or hypotheses, with a conclusion supported by evidence.

Earns marks
Points on more than one side, each backed by evidence, and a conclusion.
Watch out
One side only caps the marks. With 'Using all the data, discuss', use every table and graph given.
In exams
About 3% of parts: 1 to 4 marks to end a data question, 7 marks in Section B.
Example question and model answer

Discuss whether adding antibiotics to livestock feed should be banned. [4]

  • for a ban: it selects for antibiotic-resistant bacteria;
  • for a ban: resistant bacteria or resistance genes can spread to humans;
  • against: antibiotics reduce disease and losses in crowded livestock;
  • alternatives exist: vaccination, better hygiene, less crowding;
  • a conclusion that weighs these, e.g. ban routine use but allow treatment of sick animals;

Often confused with Evaluate, Comment.

Evaluate

AO3 · Analyse, evaluate, create

Weigh up the strengths and the limitations of something and reach an appraisal.

Earns marks
At least one strength, at least one limitation, and an overall judgement.
Watch out
A list of only strengths or only limitations is capped. Say why each one matters.
In exams
Under 1% of parts, around 3 marks.
Example question and model answer

Evaluate the use of capture-mark-release-recapture to estimate a population of woodlice. [3]

  • strength: estimates a population without counting every individual;
  • strength: suits mobile animals that cannot be counted with quadrats;
  • limitation: assumes no births, deaths or migration between samples;
  • limitation: assumes marks are not lost and do not affect survival, and that marked woodlice mix fully;
  • judgement: useful for a rough estimate if the sampling periods are short;

Often confused with Discuss, Analyse, Comment.

Explain

AO3 · Analyse, evaluate, create

Give a detailed account that includes reasons or causes: how and why.

Earns marks
Each point links a feature or event to its cause or effect.
Watch out
Describing what happens is not enough: add the because. Link each point with so, therefore or which means.
In exams
About 16% of parts: 2 to 3 marks in Section A, and the big 7 to 8 mark parts in Section B.
Example question and model answer

Explain how the structure of the alveoli is adapted for gas exchange. [4]

  • walls one cell thick, so the diffusion distance is short;
  • very many alveoli, so the total surface area is large;
  • a dense capillary network keeps blood flowing, so the concentration gradient is maintained;
  • a moist lining, so gases dissolve before diffusing;
  • surfactant reduces surface tension, so the alveoli do not collapse;

Often confused with Describe, Justify, Outline.

Justify

AO3 · Analyse, evaluate, create

Give valid reasons or evidence that support an answer or conclusion.

Earns marks
Each reason or piece of evidence, tied to the claim.
Watch out
Do not just repeat the claim. Point to the evidence, quoting data when it is given.
In exams
About 1% of parts, 2 to 3 marks.
Example question and model answer

An enzyme's activity fell from 90 units at 45 °C to 5 units at 55 °C and stayed at 5 units after cooling to 37 °C. Justify the conclusion that the enzyme was denatured. [2]

  • activity fell sharply above the optimum, from 90 to 5 units;
  • activity did not recover on cooling, so the change was permanent: the active site had changed shape;

Often confused with Explain, Evaluate.

Predict

AO3 · Analyse, evaluate, create

Give an expected result.

Earns marks
The direction of the change, and its size if the data allow.
Watch out
Give a clear result. Add a reason only if the question asks for one ('predict, with a reason').
In exams
Under 1% of parts, 1 to 4 marks.
Example question and model answer

Predict the effect of an increase in wind speed on the rate of transpiration. [1]

  • the rate of transpiration increases;

Often confused with Deduce, Suggest.

Sketch

AO3 · Analyse, evaluate, create

Draw a diagram or graph that shows the general shape or relationship, with the relevant features labelled.

Earns marks
The right shape and the key features (peaks, plateaus, where the line starts), plus labelled axes.
Watch out
An exact scale is not needed, but the shape must be right and the axes labelled.
In exams
Not seen as an opening word recently, but on the list.
Example question and model answer

Sketch a graph of the rate of an enzyme-controlled reaction against substrate concentration. [2]

  • axes labelled: rate of reaction (y) and substrate concentration (x);
  • the curve rises steeply from the origin, then levels off at a maximum rate (plateau);

Often confused with Draw, Construct.

Suggest

AO3 · Analyse, evaluate, create

Propose a solution, hypothesis or other possible answer.

Earns marks
A plausible answer that is biologically sound and fits the information given. Several answers can be accepted.
Watch out
Often set in an unfamiliar context: use biology you know. Vague answers ('it likes it there') score nothing.
In exams
About 7% of parts, 1 to 2 marks.
Example question and model answer

A moth species lives on only one small island. Suggest why it may be at greater risk of extinction than a widespread species. [1]

  • a small population / low genetic diversity, so less able to adapt to change;
  • OR nowhere else to go if its island habitat is lost;

Often confused with Predict, Deduce, Explain.

Pairs that are easy to mix up

State, Define or Identify?

State gives a fact. Define gives the exact meaning of a term. Identify picks the answer from what is in front of you.

Outline, Describe or Explain?

The same topic at three depths. Outline: the main points, briefly. Describe: the full account of what happens. Explain: adds why, the cause behind each step.

Describe or Explain a graph?

Describe: the trend, where it changes, and values with units. Explain: the biological reason for the trend.

Compare, Compare and contrast, or Distinguish?

Compare: similarities. Compare and contrast: similarities and differences. Distinguish: differences. In all three, every point mentions both things.

Analyse, Evaluate, Discuss or Comment?

Analyse: take the information apart. Evaluate: strengths against limitations, then a verdict. Discuss: several viewpoints or factors, then a conclusion. Comment: one judgement on a given result.

Deduce, Predict, Suggest or Determine?

Deduce: a conclusion that must follow from the information. Predict: an expected result. Suggest: one plausible possibility among several. Determine: the single correct answer.

Draw, Sketch, Label, Annotate or Construct?

Draw: accurate and to scale. Sketch: the general shape. Label: names only. Annotate: names plus notes. Construct: an organised form such as a table or Punnett grid.

Calculate, Estimate or Measure?

Calculate: an exact answer with working. Estimate: an approximate value. Measure: read it from a ruler or scale.

Words that change what earns marks

Not command terms, but they come with them.

Practise: 20 quick questions

Open to try them: pick an answer to see why.

Which command term? · 1 of 20

A student's answer: "The rate rises from 2 to 12 units between 0 and 400 units of light, then stays at 12 units." Which command term is this answer written for?

It gives the trend, where it changes and values, but no reasons. That is a Describe answer.

Which command term? · 2 of 20

A student's answer: "Walls one cell thick, so the diffusion distance is short." Which command term is this answer written for?

A feature linked to its effect with 'so' is an Explain point.

Which command term? · 3 of 20

A student's answer: "Phosphodiester bond." Which command term is this answer written for?

A name with no explanation answers a State question.

Which command term? · 4 of 20

A student's answer: "Both pump protons across a membrane, and both make ATP through ATP synthase." Which command term is this answer written for?

Only similarities, each about both items: in the IB definition, that is Compare.

Which command term? · 5 of 20

A student's answer: "A strength is ..., but a limitation is ...; overall the method is useful for a rough estimate." Which command term is this answer written for?

Strengths weighed against limitations, ending in a judgement, is Evaluate.

Which command term? · 6 of 20

A student's answer: "Neither parent is affected, so both must be carriers: the condition is recessive." Which command term is this answer written for?

A conclusion reached from the evidence given (a family's phenotypes) is Deduce.

Pick the best answer · 7 of 20

"Distinguish between DNA and RNA. [2]" Which answer earns both marks?

Each Distinguish point must contrast both molecules. The first answer states facts about each separately, the second gives similarities, and the third is about one molecule only.

Pick the best answer · 8 of 20

"State the optimum temperature of the enzyme shown. [1]" Which answer is best?

State wants the value with its unit, and nothing else. "40" has no unit, the third adds a detail that was not asked for, and the fourth gives no value.

Pick the best answer · 9 of 20

"Compare and contrast mitosis and meiosis. [3]" Which answer can reach full marks?

Compare and contrast needs similarities AND differences. The first answer has no similarity and the last has no difference.

Pick the best answer · 10 of 20

"Calculate the estimated population size: 40 marked, 50 caught later, 10 of them marked. [1]" Which answer is set out best?

Calculate means showing the working and giving the unit. The first answer has no working or unit, and the last one stops halfway.

Pick the best answer · 11 of 20

"Using all the data, discuss whether the drug is effective. [3]" A table and a graph are given. Which plan fits the question?

Discuss needs more than one side and a conclusion, and 'using all the data' means every source given.

Spot the problem · 12 of 20

"Describe the trend in the graph. [2]" A student wrote: "The rate increases because more enzyme molecules collide with substrate." What is wrong?

The 'because' part is a reason, which Describe does not ask for. The marks are for the shape of the trend and the values, so this answer gives a reason but no trend details or values.

Spot the problem · 13 of 20

"Evaluate the use of quadrats to estimate a plant population. [3]" A student wrote three strengths of quadrat sampling. What is the problem?

A one-sided Evaluate answer is capped: weigh strengths against limitations, then judge.

Spot the problem · 14 of 20

"Identify one abiotic factor that could limit this plant's distribution. [1]" A student wrote: "Light, pH, temperature and grazing by rabbits." What is the problem?

Give exactly the number asked for. Listing several, including grazing (a biotic factor), can cancel the right answer.

Spot the problem · 15 of 20

"Compare the two enzymes. [2]" A student wrote only differences. What does the IB definition of Compare expect?

In the IB glossary, Compare is about similarities. Differences are asked for with 'Compare and contrast' or 'Distinguish'.

Spot the problem · 16 of 20

"Draw a graph of the results. [3]" Which of these would lose marks?

Draw means accurate: a ruler for straight lines, correctly plotted points and labelled axes with units.

Upgrade the answer · 17 of 20

Describe answer: "Enzyme activity falls sharply above 40 °C." The question now says Explain. Which sentence turns it into an Explain answer?

Explain adds the cause: the change in the active site. Adding values (the first answer) makes a better Describe answer, not an Explain answer.

Upgrade the answer · 18 of 20

Outline answer: "Water moves into the root hair cell." The question is Explain [2]. What is missing?

An Explain mark needs the mechanism and its cause, not another fact or a diagram.

Upgrade the answer · 19 of 20

Answer to "Compare and contrast arteries and veins [2]": "Arteries have thick walls. Veins have valves." How would you improve it?

Compare and contrast needs a similarity (for example, both have three layers in their walls) and differences written as pairs: arteries have thick walls, whereas veins have thinner walls.

Upgrade the answer · 20 of 20

Evaluate answer: "Quadrats are quick and cheap." Which addition does most to improve it?

Evaluate needs strengths weighed against limitations, ending in a judgement.

Use them on real exam-style questions

Every lesson in the app has Paper 1B and Paper 2 questions with full markschemes, written the way the IB writes them. Mark your answers point by point and see which command terms you lose marks on.

Open the appBrowse the lessons

Meanings are in our own words, based on the glossary of command terms in the IB Biology guide (first assessment 2025, updated May 2026). For the official definitions, see the glossary in your copy of the guide.