Cambridge IGCSE Biology 0610 · Chapter 9
Transport in Animals
A large animal has cells that are nowhere near its body surface, and those cells still need oxygen and glucose delivered and carbon dioxide and urea carried away on a continuous basis. Diffusion alone is far too slow to manage that over the distances involved, which is exactly the problem a circulatory system exists to solve — and almost every mark in this chapter comes back to some version of that same transport problem.
Cambridge splits Transport in animals into four subtopics — 9.1 Circulatory systems, 9.2 Heart, 9.3 Blood vessels and 9.4 Blood — and it helps to see how tightly they depend on each other before you study any one of them in isolation. The heart only makes sense once you know what a circulatory system needs from a pump. The blood vessels only make sense once you know what pressure the heart is generating on either side. And the components of blood only matter once you know they have vessels to travel through and a pump to move them. Studied in that order, the chapter builds a single connected picture rather than four separate lists of facts.
Most of the marks students lose here are not really biology mistakes — they are precision mistakes. Saying an artery “carries oxygenated blood” sounds correct until you meet the pulmonary artery, which carries deoxygenated blood and is still, unambiguously, an artery. Saying the left ventricle is thicker “because it pumps more blood” misses the actual reason, which is pressure and distance, not volume. The pages below are written around exactly these precision points, because that is usually where the gap between what a student understands and what an examiner will credit actually sits.
What’s in this chapter
| Page | Level | What it covers |
|---|---|---|
| The circulatory system | Core | What a circulatory system actually is — a pump, a network of vessels and a set of valves working as one system — before you meet any of the detail underneath it. |
| Single and double circulation | Supplement | Why a fish heart pumping blood once per circuit and a mammal heart pumping it twice are genuinely different systems, and what mammals gain from the second pump. |
| The mammalian heart | Core + Supplement | Every heart structure Cambridge names, the route blood actually takes through it, why the chamber walls differ in thickness, how the valves open and close, and how heart activity is monitored. |
| Exercise and heart rate | Core + Supplement | How to design a fair investigation into heart rate and activity, and the respiration-based chain of reasoning behind why heart rate rises at all. |
| Coronary heart disease | Core | What actually happens when a coronary artery narrows, the seven risk factors Cambridge names, and how diet and exercise change the odds. |
| Arteries, veins and capillaries | Core + Supplement | The structural differences between the three vessel types, why each is built the way it is, and the named vessels of the heart, lungs, kidneys and liver. |
| Components of blood | Core + Supplement | Red cells, white cells, platelets and plasma — what each one transports or defends against, and how a clot actually forms. |
Core or Supplement?
Every Core candidate needs the circulatory system, the structure of the heart, how to monitor it, the exercise-and-heart-rate investigation, coronary heart disease, the basic comparison of arteries, veins and capillaries, the named vessels of the heart, lungs and kidneys, and the components and roles of blood. Supplement-only material sits inside several of those same pages rather than forming entirely separate topics: single and double circulation, the two named classes of heart valve, why the chamber walls differ in thickness, the full pressure-driven sequence of a heartbeat, why physical activity raises heart rate, why each vessel’s structure suits its job, the liver’s three named vessels, the distinction between lymphocytes and phagocytes, and the fibrinogen-to-fibrin clotting mechanism. Each page below marks clearly which parts are Core and which are Supplement as you read.