Based on a sample question
Mark points shown after marking
Explain how human lungs are adapted for rapid gas exchange.
(3)Total for this question: 3 marks
COMMAND WORD · BIOLOGY
Explain
Build a clear chain of cause and effect.
Writing frame
X because Y, meaning Z.
What the parts mean
- Xwhat happens
- Ythe biological reason
- Zthe linked consequence
How to build your answer
- 1Identify what needs explaining.
- 2Give the biological reason.
- 3Link that reason to the outcome in the question.
- 4Extend the chain when more detail is needed.
Biology exemplar
Original question
Explain why increasing light intensity can increase the rate of photosynthesis when light is the limiting factor.
Annotated answer
XThe rate of photosynthesis increases Ybecause chlorophyll absorbs more light energy, increasing the rate of the light-dependent reactions, Zmeaning more ATP and reduced NADP are available to support carbon fixation.
The labels match the frame. Read them in order. This is one accurate route, not the only one.
Exam habit
Check that your “because” explains the mechanism rather than repeats the question.
Common pitfall
Writing “photosynthesis increases because light intensity increases” without explaining how the extra light affects the process.
Exam-style question
Answer discussion
Link each adaptation to diffusion. A large exchange surface, a short diffusion distance and a maintained concentration gradient are the kinds of reason that explain a rapid rate. “Lungs are for breathing” names the organ and does not explain the rate.
Where this comes from
Unit 1 sample paper. Question 6 (a) asks how human lungs are adapted for rapid gas exchange. Sample assessment, not a live paper.
Sample paper WBI11/01, question 6 (a) (3 marks), 2017 sample assessment. Question page · Mark scheme page