Most marks in CCEA A-Level Biology are lost twice over: once by answering a different command word to the one printed, and once by writing a correct idea in wording the mark scheme does not credit. This page fixes both. Every command word CCEA uses is below with a worked answer, followed by the buzzword lists for AS 1-3 and A2 1-3 — the exact phrases that earn the mark, and the everyday wording that does not.
Open CCEA’s official past papers and mark schemesThe command word tells you the type of sentence to write; the tariff tells you how many separate points you need. Six marks means six ideas.
Named organism, tissue, temperature or figure. Every answer must be about that context, not the textbook version.
Two or three examiner-credited terms in the margin. This is what the mind maps are for — the terms are the marks.
Short, connected sentences. Never bury two ideas in one clause where a marker may miss one.
'Rose from 12 to 34 cm³ min⁻¹' scores where 'increased' does not.
Read your last sentence back: does it describe, explain, compare or evaluate as asked? If not, add the missing sentence.
19 command words, each with the structure examiners expect, the usual mark tariff, sentence stems, the trap that loses marks, and a full-mark worked answer in CCEA wording.
Give a short fact with no reasoning. The mark is for recall alone.
One clause. No 'because'. No hedging with a second guess.
Writing a paragraph. A wrong extra sentence after a correct one can cancel the mark.
State the site of the light-dependent stage of photosynthesis. (1)
The thylakoid membranes of the chloroplast.
Identical demand to State — a fact, a figure or a named example, drawn from the stem or from recall.
Answer only what is asked. If asked for one, give one.
Listing three answers when one is asked for — CCEA marks the first answer given.
Give one advantage of the counter-current flow in a fish gill. (1)
A diffusion gradient for oxygen is maintained across the whole length of the gill lamella.
Supply the correct biological term, spelt correctly.
The term alone. Precision of the noun phrase is the mark.
Near-miss spellings that read as another term (e.g. 'ureter' for 'urethra') are not credited.
Name the enzyme that catalyses the fixation of carbon dioxide in the Calvin cycle. (1)
Rubisco (ribulose bisphosphate carboxylase).
Give the precise biological meaning of a term, in the terms CCEA uses for it.
Full definition sentence including any measurable condition (standard conditions, per unit area, etc.).
Using the term inside its own definition, or dropping the qualifying condition.
Define water potential. (2)
Water potential is the tendency of water molecules to move from one place to another, measured in kilopascals; pure water at standard temperature and pressure has a water potential of zero.
Pick out the correct item from a diagram, graph, table or list.
Name the item and, if asked, quote the letter or figure that locates it.
Describing the item instead of naming it.
Identify the stage of mitosis shown in the photomicrograph. (1)
Metaphase — the chromosomes are aligned along the equator of the cell.
Say what happens, in the right order, without giving reasons.
Sequenced points, one marking point per idea. With data, quote figures and units.
Slipping into explanation. 'Because' sentences waste time and score nothing here.
Describe the changes in membrane potential during an action potential. (4)
The membrane depolarises as voltage-gated sodium channels open and sodium ions enter, raising the potential from -70 mV to about +40 mV. The sodium channels then close and voltage-gated potassium channels open, so potassium ions leave and the membrane repolarises. The potential briefly falls below -70 mV in hyperpolarisation before the sodium-potassium pump restores the resting potential.
Give the reason or the mechanism. Each distinct 'because' is a separate mark.
Statement, then the causal link, then the consequence. Chain the biology all the way to the outcome.
Describing the process again. If your answer would score on a 'Describe' question, it is not an explanation.
Explain why the loop of Henle allows the production of concentrated urine. (4)
Sodium ions are actively transported out of the ascending limb, so the water potential of the medullary tissue fluid is lowered. Because the descending limb is permeable to water, water leaves it by osmosis down the water potential gradient. This counter-current multiplier maintains a low water potential deep in the medulla, so as the collecting duct passes through it water is reabsorbed by osmosis and the urine becomes concentrated.
Give the main stages only — breadth rather than depth.
Short numbered stages covering the whole process; do not develop any one stage.
Writing a full essay on the first stage and running out of time before the rest.
Outline the stages of aerobic respiration. (4)
Glycolysis in the cytoplasm splits glucose into two pyruvate molecules. The link reaction converts pyruvate into acetyl coenzyme A in the mitochondrial matrix. The Krebs cycle releases carbon dioxide and reduced NAD and FAD. Oxidative phosphorylation on the inner mitochondrial membrane uses these to generate ATP.
Make linked statements covering both things in the same sentence.
Use comparative connectives: 'whereas', 'in contrast', 'both'. Cover similarities and differences if the question says 'compare'.
Two separate lists. An unlinked list of features about each item scores very little.
Compare xylem vessels and phloem sieve tubes. (3)
Both are tubular transport tissues running through the vascular bundle, but xylem vessels are dead lignified cells with no end walls whereas sieve tubes are living cells with perforated sieve plates. Xylem carries water and mineral ions upwards only, in contrast to phloem which translocates sucrose in either direction. Xylem transport is passive whereas translocation requires ATP from companion cells.
Differences only — no similarities are credited.
Paired opposites in one sentence each.
Opening with what the two have in common. It earns nothing.
Contrast mitosis and meiosis. (2)
Mitosis produces two genetically identical diploid cells whereas meiosis produces four genetically different haploid cells. Homologous chromosomes pair and cross over in meiosis, which does not happen in mitosis.
Apply what you know to an unfamiliar context. There is usually more than one creditworthy answer.
Commit to one biologically sound idea and justify it with named biology from the spec.
Writing 'I don't know but maybe'. Vague guesses without named biology score nothing.
Suggest why the rate of transpiration continued to fall after the stomata had closed. (2)
Some water vapour still diffuses through the waxy cuticle, so the rate falls rather than stopping; as the leaf air spaces become saturated the water potential gradient between leaf and air is reduced, lowering the rate further.
Link a structural or physiological feature to a measurable benefit or cost to the organism.
Feature → mechanism → benefit to survival or efficiency.
Stopping at the mechanism without naming the advantage.
Explain one advantage of the many mitochondria in a proximal convoluted tubule cell. (2)
Mitochondria release ATP by oxidative phosphorylation, and this ATP is required for the active transport of glucose and sodium ions, so selective reabsorption can occur against a concentration gradient.
Work out a numerical answer and show every step.
Write the formula, substitute values, give the answer to the stated number of significant figures with units.
No working and no units. A wrong final figure with correct working still earns method marks.
A cell measures 30 mm on a photograph taken at ×1500. Calculate its actual length in µm. (2)
actual = image ÷ magnification = 30 mm ÷ 1500 = 0.02 mm = 20 µm.
Produce or finish a table, graph, diagram or genetic cross.
Axes labelled with quantity and unit, sensible scale using over half the grid, points plotted accurately, line or curve of best fit drawn thinly.
Unlabelled units, a broken scale without a zigzag, or joining points dot-to-dot when a curve is expected.
Plot the data to show the effect of temperature on enzyme activity. (3)
Temperature (°C) on the x-axis, rate of reaction (cm³ min⁻¹) on the y-axis, linear scales filling the grid, points plotted with neat crosses and a smooth curve of best fit.
Reach a conclusion that the given data or pedigree forces you to.
Quote the evidence, then state what it must mean.
Stating the conclusion without citing the evidence that proves it.
Deduce the mode of inheritance shown in the pedigree. (2)
Two unaffected parents have an affected daughter, so the allele is recessive; because an affected female occurs it cannot be Y-linked, and as her father is unaffected it is autosomal recessive.
Say what will happen next, using the biological pattern in the data.
State the direction of change and, where the data allow, an approximate figure.
Answering 'it would change' without a direction.
Predict the effect of adding a competitive inhibitor on the rate at high substrate concentration. (2)
The rate would be almost unchanged at high substrate concentration, because substrate molecules outcompete the inhibitor for the active site.
Defend a choice, method or conclusion with evidence.
Claim, then evidence, then why alternatives are weaker.
Repeating the claim in different words instead of supplying evidence.
Justify the use of a water bath in this investigation. (2)
The water bath keeps temperature constant, so it is controlled as a variable; without it any change in rate could be caused by temperature rather than by the independent variable.
Weigh strengths against limitations and reach a supported judgement.
Strengths, limitations, then an explicit verdict. Extended responses carry QWC credit.
Listing pros and cons and never giving the judgement, which is where the final marks sit.
Evaluate the reliability of the student's conclusion. (4)
The student repeated each concentration three times and the results were close, so the data are reasonably reproducible. However, only three concentrations were tested and temperature was not controlled with a water bath, so the trend is not securely established. Overall the conclusion is supported in direction but not in magnitude, and further repeats over a wider range are needed.
Explore a biological issue from more than one angle and reach a balanced conclusion.
Two or more developed viewpoints with named biology, then a conclusion. QWC is assessed: logical order, correct terminology, accurate spelling and grammar.
Bullet points. CCEA extended responses need continuous, connected prose to gain the QWC marks.
Discuss the biological consequences of eutrophication in a freshwater river. (6)
Leached nitrate and phosphate enrich the water, so algal populations grow rapidly and form an algal bloom that blocks light from submerged plants. Those plants die and saprobiotic bacteria decompose them, and because aerobic respiration by these bacteria consumes dissolved oxygen the biochemical oxygen demand rises sharply. Fish and invertebrates with a high oxygen requirement, such as mayfly nymphs, die or migrate, while tolerant species such as Tubifex increase, so species diversity falls. In conclusion, eutrophication changes community structure mainly by lowering dissolved oxygen rather than by direct toxicity.
Grouped by specification unit. Use the credited phrase, not the everyday one.
condensation reaction / hydrolysis
not “joining together / breaking apart”
CCEA credits the named reaction, and the water molecule released or used must be mentioned.
glycosidic bond, peptide bond, ester bond
not “chemical bond”
The specific bond name is the marking point in every biological-molecules question.
complementary shape to the active site
not “fits the active site like a jigsaw”
'Complementary' is the credited word; 'same shape' is rejected.
enzyme-substrate complex
not “the enzyme sticks to the substrate”
Almost every enzyme mechanism mark depends on naming this complex.
lowers the activation energy
not “speeds up the reaction”
The mechanism mark requires activation energy, not just rate.
denatured — tertiary structure altered, active site no longer complementary
not “the enzyme is killed / destroyed”
'Killed' is never credited; the three-part chain earns three separate marks.
water potential gradient
not “concentration of water”
CCEA marks osmosis in water-potential terms only, measured in kPa and always negative in solutions.
partially permeable membrane
not “semi-permeable membrane”
CCEA uses 'partially permeable' in its schemes.
facilitated diffusion through a channel or carrier protein
not “diffusion through a hole”
The named protein is the mark.
active transport requires ATP against the concentration gradient
not “the cell pushes it in”
Both ATP and 'against the gradient' are separate marking points.
sodium-potassium pump
not “sodium-potassium ATPase”
CCEA's term is the pump; the ATPase wording belongs to other specifications.
large surface area to volume ratio
not “big surface area”
The ratio, not the area alone, is what CCEA credits in exchange questions.
short diffusion pathway / distance
not “thin”
'Thin' alone is usually insufficient without the diffusion consequence.
counter-current flow maintains the diffusion gradient
not “blood and water flow opposite ways”
The consequence for the gradient is the second mark.
tissue fluid
not “interstitial liquid”
CCEA names it tissue fluid, formed by hydrostatic pressure at the arteriole end.
hydrostatic pressure and oncotic (solute) pressure
not “pressure”
Capillary exchange marks depend on distinguishing the two pressures.
cohesion-tension theory, transpiration pull
not “water is sucked up”
'Sucked' is rejected; the named theory earns the mark.
species richness and species evenness
not “how many species there are”
Biodiversity questions expect both components of diversity.
resting potential of -70 mV, polarised membrane
not “no charge”
The figure and the word 'polarised' are both creditworthy.
depolarisation, repolarisation, hyperpolarisation
not “the charge changes”
Each named stage is a separate marking point.
voltage-gated sodium / potassium channels
not “gates open”
The ion and the gating mechanism must both be named.
saltatory conduction between nodes of Ranvier
not “it jumps along”
The named term plus the node earns full credit.
refractory period ensures unidirectional impulse
not “it can only go one way”
The reason must be tied to the refractory period.
exocytosis of neurotransmitter into the synaptic cleft
not “the chemical is let out”
Exocytosis and the named cleft are both marks.
sliding filament theory, actin, myosin, tropomyosin, troponin
not “the muscle shortens”
Muscle contraction marks are awarded for the named proteins and the theory.
negative feedback restores the set point
not “the body balances itself”
'Negative feedback' and 'set point' are the credited terms.
ultrafiltration, selective reabsorption, osmoregulation
not “filtering and taking back”
Each named process maps to a named region of the nephron.
counter-current multiplier in the loop of Henle
not “the loop concentrates urine”
This single phrase is one of the most commonly missed A2 marks.
ADH increases the permeability of the collecting duct to water
not “ADH saves water”
The mechanism — aquaporins and permeability — carries the mark.
gross primary productivity and net primary productivity
not “energy made by plants”
NPP = GPP − respiratory loss; both terms are needed.
saprobiotic nutrition, nitrification, denitrification
not “bacteria break things down”
Named processes and named bacteria are the marking points in nutrient cycles.
photolysis of water, photophosphorylation, reduced NADP
not “light splits water and makes energy”
Each named reaction and product is a distinct mark.
rubisco fixes CO₂ to RuBP forming GP, reduced to TP
not “carbon is turned into sugar”
The Calvin cycle is marked on named intermediates.
oxidative phosphorylation, chemiosmosis, ATP synthase
not “ATP is produced in the mitochondria”
The proton gradient across the inner membrane must be named.
monohybrid and dihybrid inheritance, homozygous, heterozygous, phenotype, genotype
not “the gene for it”
Genetics answers are marked on precise use of allele and genotype language.
codominance, multiple alleles, sex linkage, autosomal linkage
not “both show up”
Naming the inheritance pattern is usually the first mark of the question.
chi-squared test, null hypothesis, degrees of freedom, p = 0.05
not “the results were close enough”
Statistical conclusions must reference the critical value and probability.
gene pool, allele frequency, selection pressure, reproductive isolation, speciation
not “animals change over time”
Evolution marks require population-level vocabulary — but CCEA does not require Hardy-Weinberg.
independent, dependent and controlled variables
not “the thing I changed”
Planning marks are awarded for correctly classifying every variable.
repeat readings to identify anomalies and calculate a mean
not “do it three times to be accurate”
Repeats improve reliability, not accuracy — CCEA marks the distinction.
reliability, accuracy, precision, resolution of the apparatus
not “it was a good result”
Evaluation marks depend on using these four terms correctly.
control experiment to show the effect is due to the independent variable
not “a normal test tube”
The purpose of the control is the mark, not its existence.
quantitative data with units and significant figures
not “it went up”
Data-handling marks require figures quoted from the table or graph.
Knowing the buzzwords only pays when you write them under time. Take a CCEA-style question, answer it, and get the missing marking points back instantly.
