A student fills flexible tubing with water to model blood flow through a vein. Two flexible flaps inside the tubing open towards a collecting beaker. The student repeatedly presses and releases the tubing between the flaps.
Why does water move progressively towards the collecting beaker?
Pressing pushes water forwards, and the flaps close whenever water starts to flow back.
Pressing raises the pressure in the tubing, so water flows forwards without needing the flaps.
Releasing the tubing draws water forwards, and the flaps close while the tubing is pressed.
The flaps contract after each press, pumping the water forwards towards the beaker.
67 exam-style questions on Edexcel GCSE Biology 8.2 Blood and circulation, covering 8.2.1 Structure and function of the blood, 8.2.2 Structure of blood vessels, 8.2.3 Structure of the heart and circulatory system, and 8.2.4 Cardiac output. Each one has a worked solution and a mark scheme showing where the marks go.