Pearson Edexcel International GCSE Biology · specification 4BI1 · Paper 2 | Whole paper: All content including bold B statements · Free · no account needed
2(g) Gas exchange (4BI1 specification)
How gases move in and out of plants and humans, and the surface adaptations that make it fast enough.
Learn it on Incandio
The 5 Incandio pages that teach this — each explained in full, then proved in marked questions, taught back to an AI pupil and defended in a debate. Completely free.
- The Leaf: Structure and Gas Exchange — Every feature of a leaf is a solution to one conflict — letting carbon dioxide in through holes that also let water out.
- The Thorax and Ventilation — You cannot suck air in. Breathing works by changing the size of a sealed box — and every part of the chest is built for that one job.
- Alveoli, Exercise and Smoking — Why a lung holds a tennis court's worth of surface, what exercise does to breathing, and exactly how smoking dismantles both.
- Why Transport Systems Exist, and the Two Plant Vessels — Diffusion is fast across a cell and hopeless across a body. That single fact explains why big organisms need plumbing — and what a plant's two pipes carry.
- Gas Exchange in Plants, Day and Night — Two opposite processes in one leaf, one of which never stops — and why what you can measure at the surface is only the difference between them.
The teaching route this belongs to: Topic 2 · Structures and functions in living organisms (Biology) — the lessons in order, with every gate.
Specification coverage
Topic 2 Structures and functions in living organisms (g) Gas exchange — statements 2.42–2.52B (includes bold B statements assessed on Paper 2 only)
Assessment objectives: AO1, AO2, AO3. Suggested learning time: 70 minutes.
Required knowledge
- Gas exchange in flowering plants, including the role of stomata and the effect of light
- The structure of the human thorax and the mechanism of ventilation
- The adaptations of the alveoli for gas exchange: large surface area, thin walls, moist surface, good blood supply
- The differences in composition between inspired and expired air
- Bold B statements: the effect of exercise on breathing in greater depth
Required skills
- Explain an adaptation by linking structure to rate of diffusion
- Describe ventilation as a pressure-driven process
- Interpret data comparing inspired and expired air
- Describe and evaluate the required practical: Investigate the effect of exercise on breathing rate, and the composition of inhaled and exhaled air.
How it is examined
- Multiple-choice and short-answer recall
- Application of the content to an unfamiliar context
- Extended open-response, marked on the quality of a connected explanation
- Practical questions on method, variables, data and sources of error
Common mistakes
- Saying air is 'sucked in'. The diaphragm and intercostal muscles change the volume of the thorax, which changes the pressure, and air moves down the pressure gradient.
- Claiming expired air contains no oxygen. It contains about 16%.
- Listing alveolar adaptations without saying what each one does to the rate of diffusion.
This page maps the specification. The pages above teach it, and the Biology lessons hold the whole course — completely free.