Edexcel IGCSE Biology: Command words and keywords

Pearson Edexcel International GCSE Biology (4BI1) uses the command words defined in the specification (Appendix 5). Recent specification updates added “Which” to the taxonomy. Mark schemes and examiner guidance emphasise point-marked vs levels-based questions and the importance of scientific terminology.

Command words in Edexcel Biology 4BI1

Point-marked questions (direct mark allocation)

Command word	What to do	Common mistake
State / Name / Give	Recall; short answer	Overwriting
Identify	Choose from information given	Adding explanation
Which	Select from options given	Not using the options
Define	One precise definition	Vague or long definition
Describe	Account of what/how	Adding “why” (that’s Explain)
Explain	How or why; use “because”	Only describing
Give a reason	Say why; only the number asked for	Too many or too few reasons
Suggest	Apply to new situation	Textbook recall only
Calculate	Work out; show working; units	Missing units or working
Plot	Graph from data; line of best fit	Wrong scale or no line
Draw / Label	Diagram; accurate labels	Inaccurate or unlabelled
Compare	Similarities and differences	No comparative language

Levels-based questions (mark bands)

Command word	What to do	Common mistake
Evaluate	Judge; conclude with evidence	No conclusion
Assess	Judge importance; conclude	Description only
Discuss	Explore aspects; conclude	One-sided answer
Justify	Support with evidence	Unsupported claim

Edexcel-specific: “Suggest”

Suggest is always used with another command word (e.g. “Suggest an explanation”, “Suggest a reason”). It tells you to apply knowledge to a new or unfamiliar context. Generic answers from the textbook rarely score well.

Keywords examiners look for

Edexcel mark schemes reward syllabus terminology. Correct scientific terms are credited; vague language often is not.

Cell biology and organisation

Term	Use correctly	Avoid
Mitochondria	Aerobic respiration	Ribosomes (different organelle)
Ribosome	Protein synthesis	Mitochondria
Osmosis	Water; partially permeable membrane	Including solutes
Diffusion	Down concentration gradient	Against gradient
Active transport	Against gradient; energy; carrier proteins	Without membrane
Concentration gradient	Difference in concentration	Vague “difference”

Enzymes and homeostasis

Term	Use correctly	Avoid
Optimum	Best conditions	”Ideal”
Denature	Shape change; loss of function	”Destroy” or “kill”
Substrate	Molecule enzyme acts on	Wrong term
Absorption	Into blood	Assimilation
Assimilation	Into cells/tissues	Absorption

Organ systems

Term	Use correctly	Avoid
Kidney	Excretes urea; forms urine	Bladder (stores only)
Alveolus	Gas exchange	”Lungs” when structure matters
Villus	Absorption in small intestine	Wrong spelling/function
Capillary	Exchange surface	Wrong vessel

Inheritance

Term	Use correctly	Avoid
Allele	Form of a gene	”Gene” when allele is meant
Genotype	Genetic makeup (e.g. BB, Bb)	Phenotype
Phenotype	Observable characteristic	Genotype
Dominant	Expressed when pair has one allele	Recessive
Recessive	Only expressed when pair has two	Dominant

Practical skills

Term	Use correctly	Avoid
Independent variable	What you change	”Input”
Dependent variable	What you measure	”Output”
Control variable	Kept constant	”Control” when you mean control experiment
Reliability	Repeatability	”Accuracy”
Validity	Fair test; measures what it should	”Reliability”

Edexcel marking principles

Recent Edexcel mark schemes state:

• Apply positively—reward what candidates show.
• Best-fit for levels-based questions.
• Mark crossed-out work unless replaced.
• Check working—method marks can apply even if the final answer is wrong.

What examiner reports highlight

• Command words ignored—candidates answer in the wrong style.
• Suggest answered with recall instead of application.
• Explain without “because” or cause–effect links.
• Compare without comparative language.
• Keywords missed—everyday language instead of scientific terms.
• Units omitted in calculations.

Tips for Edexcel Biology 4BI1

1. Underline the command word before answering.
2. Check “Give a reason”—only give the number of reasons requested.
3. For Suggest: Apply to the specific scenario in the question.
4. Use syllabus terms—check the mark scheme for acceptable wording.
5. Show working in calculations—method marks are available.
6. Past papers + mark schemes show exactly what scores.

How Tutopiya helps

Tutopiya supports Edexcel IGCSE Biology with tutors who use the 4BI1 specification, past papers and mark schemes. Explore IGCSE resources or book a free trial.

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Based on Pearson Edexcel International GCSE Biology 4BI1 specification. Check the latest specification for your exam series.