IGCSE Biology: Transport in Animals Practice Questions
Humans have a double circulatory system: blood passes through the heart twice for each complete circuit of the body. The right side pumps deoxygenated blood to the lungs and the left side pumps oxygenated blood to the rest of the body.
Topic 9 of Cambridge IGCSE Biology 0610 is the topic where students most often lose marks by describing a structure without explaining what it achieves. Every heart and blood vessel question should link a structural feature to a function. The questions below train that link directly.
What you need to know for Transport in Animals
- Double circulationBlood passes through the heart twice per circuit. The pulmonary circulation carries blood to the lungs and back, and the systemic circulation carries blood to the body and back.
- Heart structureFour chambers: two atria receiving blood and two ventricles pumping it out. The septum separates the two sides, and valves prevent backflow.
- ArteryCarries blood away from the heart at high pressure. It has a thick muscular and elastic wall and a narrow lumen, and no valves except at the base of the main arteries.
- VeinCarries blood towards the heart at low pressure. It has a thin wall, a wide lumen and valves to prevent backflow.
- CapillaryA wall one cell thick and a very narrow lumen. This gives a short diffusion distance and a large surface area for exchange of substances with the tissues.
- Blood componentsRed blood cells carry oxygen as oxyhaemoglobin. White blood cells defend against pathogens by phagocytosis or antibody production. Platelets are involved in clotting. Plasma carries dissolved substances, cells and heat.
IGCSE Biology Transport in Animals questions and answers
4 exam-style questions written to the 0610 syllabus. Try each one on paper first, then open the worked answer to check your method against the marks.
Explain why the wall of the left ventricle is much thicker than the wall of the right ventricle.
Show the worked answer
- The right ventricle pumps blood only to the lungs, which are close to the heart and contain delicate capillaries.
- The left ventricle pumps blood to the whole body, a much greater distance against greater resistance.
- A thicker, more muscular wall contracts with greater force and generates a higher blood pressure.
- That higher pressure is needed to push the blood all the way round the systemic circulation and back to the heart.
Compare the structure of an artery with that of a vein. Give two structural differences and explain how each relates to the function of the vessel.
Show the worked answer
- Difference 1: an artery has a thick, muscular and elastic wall, whereas a vein has a thin wall. The thick wall withstands and maintains the high pressure of blood leaving the heart, and the elastic recoil keeps blood moving between heartbeats.
- Difference 2: an artery has a narrow lumen, a vein has a wide lumen. The wide lumen of a vein reduces resistance to the low pressure blood flowing back to the heart.
- A third acceptable difference: veins contain valves and arteries generally do not.
- Valves prevent backflow in veins, where the pressure is too low to guarantee one directional flow on its own.
Describe three ways in which a red blood cell is adapted to transport oxygen.
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- It is packed with haemoglobin, which combines reversibly with oxygen to form oxyhaemoglobin in the lungs and releases it in respiring tissues.
- It has no nucleus, which leaves more room for haemoglobin so each cell carries more oxygen.
- It is a biconcave disc, which increases the surface area to volume ratio for faster diffusion of oxygen in and out.
- It is also small and flexible, so it can squeeze through narrow capillaries.
Explain one advantage of a double circulatory system compared with a single circulatory system.
Show the worked answer
- In a single circulation, blood passes through the capillaries of the gas exchange organ and then travels straight on to the body.
- Passing through capillaries greatly reduces blood pressure, so the blood then moves slowly to the tissues.
- In a double circulation the blood returns to the heart after the lungs and is pumped again at high pressure.
- This means oxygen and nutrients are delivered to respiring tissues more quickly, supporting a higher rate of metabolism.
Common mistakes in this topic
- Labelling the left and right sides of a heart diagram from the reader's point of view. They are labelled from the point of view of the person the heart belongs to.
- Saying arteries always carry oxygenated blood. The pulmonary artery carries deoxygenated blood.
- Describing a structural feature without the function it serves.
- Confusing atria with ventricles. Atria receive blood, ventricles pump it out.
- Writing that white blood cells eat germs. Use phagocytosis and antibody production.
Exam tips
- Learn the four chambers and four main vessels as a circuit you can draw from memory in thirty seconds.
- For any adaptation question, write feature plus so that plus advantage. That structure earns the explanation mark.
- Remember the exceptions: pulmonary artery carries deoxygenated blood, pulmonary vein carries oxygenated blood.
- Coronary arteries supply the heart muscle itself. Blockage causes a heart attack, and risk factors include diet high in saturated fat, smoking, stress and lack of exercise.
- When given exercise data, link an increased heart rate to increased delivery of oxygen and glucose and increased removal of carbon dioxide.
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Transport in Animals FAQs
What is a double circulatory system?
A double circulatory system is one in which blood passes through the heart twice for each complete circuit of the body. The pulmonary circulation takes blood from the heart to the lungs and back, and the systemic circulation takes it from the heart to the rest of the body and back. This restores blood pressure after the lungs.
Why is the left ventricle wall thicker than the right?
The left ventricle pumps blood around the whole body, which requires a much higher pressure than pumping blood the short distance to the lungs. A thicker layer of muscle contracts with more force, generating the higher pressure needed. Both ventricles pump the same volume of blood.
Do arteries always carry oxygenated blood?
No. An artery is defined as a vessel that carries blood away from the heart, regardless of oxygen content. The pulmonary artery carries deoxygenated blood from the heart to the lungs, and the pulmonary vein carries oxygenated blood from the lungs back to the heart.
How is a red blood cell adapted to its function?
It contains haemoglobin, which binds oxygen reversibly. It has no nucleus, leaving more space for haemoglobin. It is a biconcave disc, giving a large surface area to volume ratio for rapid diffusion. It is also small and flexible enough to pass through narrow capillaries.
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Written to the published Cambridge IGCSE Biology (0610) syllabus. Check your school entry code and syllabus year, because Core and Extended candidates are assessed on different content. Last reviewed 2026-08-12.