KS4: Teachers could explore the need for blood donation, the reasons for giving blood (altruism), variance in global blood supply and demand (inequality), social responsibility (who should donate?), ethical dilemmas (Jehovah's Witnesses and operations), or use case studies of lives saved by blood transfusions.
One area for enquiry might be "Should blood donation be made compulsory by law?" where tensions between individual freedom of choice and social responsibility can be investigated. As a first step, go to www.blood.co.uk, or try the brief list of "interesting blood facts" at www.heart-transplant.co. uk