This comprehensive GCSE Trilogy Biology work pack covers the full AQA specification content on the organisation of the circulatory and respiratory systems. It is designed to support revision, retrieval practice, exam preparation and deeper application skills. ✔ Includes: Heart structure & double circulation Key blood vessels (aorta, vena cava, pulmonary artery & vein) Pacemaker & control of heart rate Lung structure & gas exchange (alveoli adaptations) Arteries, veins & capillaries (structure–function links) Blood components & microscope recognition Blood flow calculations CHD, stents, statins & valve replacements Multiple-choice, exam-style and higher-tier application questions Full answer key included Perfect for revision, homework, intervention or cover lessons.