12.1 Transport systems
Mass transport Over large distances in organisms, efficient supply of materials is
provided by mass transport (the bulk movement of substances
through transport systems).
The transport systems of larger organisms are intimately linked with
specialised exchange systems, whose main function is to maintain
Mammalian heart The structure and function of the heart, including the atria and
ventricles, atrioventricular and semilunar valves. The cardiac cycle
related to the maintenance of blood flow through the heart.
Candidates should be able to relate pressure and volume changes
in the heart and aorta to events in the cardiac cycle.
Blood vessels The structure of arteries, arterioles, veins and capillaries related to
Exchange of materials The main substances transported by the blood system, and the sites
at which exchange occurs.
The loading, transport and unloading of oxygen in relation to the
oxygen haemoglobin dissociation curve, and the effects of pH and
carbon dioxide concentration.
Tissue fluid The relationship between blood, tissue fluid, lymph and plasma.
The role of the lymph system in the return of tissue fluid to the
12.2 The control of breathing and
Control of ventilation The role of the medulla in the brain and of the stretch receptors in
the lungs in the maintenance of breathing.
The role of the medulla in the brain and of the receptors in the
lungs, aortic bodies and carotid bodies in the response of the
breathing system to increased muscular activity.
Control of heartbeat The role of the sinoatrial node, the atrioventricular node and the
bundle of His in the maintenance of the heartbeat.
The role of the medulla, pressure receptors and chemoreceptors in
the walls of the aorta and carotid sinuses in the response of the
heart to increased muscular activity.
12.3 Energy and exercise
Energy sources Glucose, glycogen and triglycerides as sources of energy for muscle
ATP as the immediate energy source.
Comparison of aerobic and anaerobic respiration as sources of ATP
for muscle contraction, in terms of amounts of energy produced
and products. (Biochemical details of pathways are not required.)
Muscle fatigue Muscle fatigue in terms of increase in blood lactate and decrease in
The fate of lactate.
12.4 The transport of substances in
Root structure Structure of a primary root, to include root hairs, endodermis,
xylem and phloem. The distribution of these tissues and their
adaptations for function.
Uptake and the transpiration
Uptake of water and ions from the soil.
Pathway of transport of water from root hairs to stomata, including
apoplast and symplast pathways in the root.
Transpiration, and the effects of light, temperature, humidity and
The roles of root pressure and cohesion–tension in moving water
through the xylem.
Xerophytes Structural adaptations that reduce the rate of transpiration in
xerophytic plants, related to survival in dry conditions.
Translocation Phloem as the tissue that transports organic substances.
The mass flow hypothesis for the mechanism of translocation in
Experimental evidence The use of radioactive tracers and ringing experiments to determine
the movement of ions and organic substances through plants.
Candidates should be able to interpret evidence from tracer and
ringing experiments and to evaluate the evidence for and against the
mass flow hypothesis.