OCR A Level Biology A
OCR A Level Biology A Module 3: Exchange and Transport Exam Questions
Free OCR A Level Biology A exam questions for Module 3: Exchange and Transport, with a mark scheme for every pack. Covers surface area to volume ratio, mammalian, fish and insect gas exchange, the heart, blood vessels, haemoglobin and transport in plants.
Module 3: Exchange and Transport exam questions
3 question packs of real past exam questions, each with its mark scheme. Do not stop after a few: answer as many as you can without notes, then mark every answer with the mark scheme. The more questions you do, the more quickly you will spot how examiners ask about each idea.
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About OCR A Level Biology A Module 3: Exchange and Transport
Module 3 of OCR A Level Biology A, Exchange and Transport, explains why larger multicellular organisms need specialised exchange surfaces and mass transport systems. It covers ventilation and gas exchange in mammals, bony fish and insects, the mammalian circulatory system and heart, haemoglobin and oxygen transport, and transport of water and assimilates in plants. It builds on membranes from Module 2 and supports respiration in Module 5. Examiners often use spirometer traces, cardiac cycle pressure graphs, ECGs, oxygen dissociation curves and potometer results, and expect precise use of terms like tidal volume and cohesion-tension.
What you need to know
- 3.1.1 Surface area to volume ratio and features of efficient exchange surfaces, the mammalian gaseous exchange system and ventilation, spirometer traces (tidal volume, vital capacity, breathing rate, oxygen uptake), and ventilation in bony fish and insects.
- 3.1.2 Circulation and the heart Single, double, open and closed circulatory systems, arteries, arterioles, capillaries, venules and veins, tissue fluid formation, the structure of the heart and cardiac cycle, the SAN, AVN and Purkinje tissue, and ECGs.
- 3.1.2 Blood and haemoglobin Haemoglobin and the oxygen dissociation curve, the Bohr effect, fetal haemoglobin, and carbon dioxide transport as hydrogencarbonate ions with carbonic anhydrase and the chloride shift.
- 3.1.3 Structure and function of xylem and phloem, the symplast and apoplast pathways, transpiration and the factors affecting it, the potometer, water uptake and movement, adaptations of xerophytes and hydrophytes, and translocation by mass flow with active loading of sucrose.
Common mistakes in Module 3: Exchange and Transport
- Saying insects breathe through their trachea using lungs. Insects take air in through spiracles into tracheae and tracheoles, which deliver oxygen directly to tissues.
- Describing tissue fluid formation without hydrostatic and oncotic pressure. At the arteriole end, hydrostatic pressure exceeds oncotic pressure so fluid is forced out; at the venule end, oncotic pressure draws water back in.
- Stating that the right ventricle has a thicker wall because it pumps more blood. The left ventricle has the thicker wall because it pumps blood at higher pressure around the whole body.
- Saying sucrose moves through phloem by diffusion. Translocation is by mass flow, driven by active loading at the source creating a hydrostatic pressure gradient.
- Reading oxygen uptake from a spirometer without considering the trace slope. Oxygen consumption is shown by the overall downward slope of the trace as carbon dioxide is absorbed by soda lime.
Try three Module 3: Exchange and Transport exam-style questions
1. A person has a tidal volume of 0.5 dm3 and a breathing rate of 12 breaths per minute. Calculate their ventilation rate. (1 mark)
Show the mark scheme answer
0.5 x 12 = 6.0 dm3 per minute.
2. Explain how the cardiac cycle is coordinated. (4 marks)
Show the mark scheme answer
SAN generates a wave of excitation causing the atria to contract; a layer of non-conducting tissue prevents the wave passing directly to the ventricles; AVN delays the impulse so atria empty first; impulse travels down the bundle of His and Purkinje fibres; ventricles contract from the apex upwards.
3. Describe how xerophytes are adapted to reduce water loss. (3 marks)
Show the mark scheme answer
Thick waxy cuticle; sunken stomata or stomata in pits; hairs trap moist air; rolled leaves; reduced leaf surface area such as spines; any three, each linked to reduced water potential gradient or reduced evaporation.
Module 3: Exchange and Transport FAQs
What does OCR A Level Biology A Module 3: Exchange and Transport cover?
Exchange surfaces and ventilation, transport in animals including the heart and haemoglobin, and transport in plants.
Which papers is Module 3 examined in?
At A Level it is assessed in Paper 1 (Biological processes) and Paper 3 (Unified biology); it is also assessed at AS.
How do I interpret a spirometer trace?
Read tidal volume from the height of a normal breath, vital capacity from the deepest breath, breathing rate from the number of peaks per minute, and oxygen uptake from the downward slope of the trace.
