This guide covers IGCSE Biology topic 14 (part 2): coordination and response – hormones. You will revise adrenaline (fight or flight), insulin (blood glucose), ADH (water balance), and plant hormones (auxin: phototropism, gravitropism).

Key concepts to revise

• Hormone – Chemical produced by a gland; carried in blood; has effect on target organ. Slower than nervous response; longer-lasting.
• Adrenaline – From adrenal gland; increases heart rate, breathing, blood flow to muscles; prepares for fight or flight.
• Insulin – From pancreas; lowers blood glucose (stimulates liver and muscles to take up glucose). Lack leads to diabetes.
• Auxin – Plant hormone; uneven distribution causes phototropism (bend towards light) and gravitropism (roots down, shoots up).

Exam tips and command words

• State – Where the hormone is produced and what it does (e.g. Insulin is produced by the pancreas and lowers blood glucose).
• Describe – The effect of adrenaline on heart rate and breathing; the effect of auxin on shoot growth (more auxin on shaded side, bend towards light).
• Compare – Nervous vs hormonal response (speed, duration, transmission: electrical vs blood).
• Explain – Why insulin is needed (glucose enters cells; without insulin, blood glucose stays high).

Common mistakes

• Saying insulin produces or stores glucose (insulin lowers blood glucose by stimulating uptake and storage).
• Confusing phototropism (response to light) with gravitropism (response to gravity).
• Not stating that hormones are carried in the blood and act on target organs.

Revision checklist

• State where adrenaline, insulin and ADH are produced and their main effects.
• Describe how blood glucose is regulated (insulin lowers; glucagon raises if on syllabus).
• Explain phototropism and gravitropism in terms of auxin distribution.
• Compare nervous and hormonal coordination (speed, how signal is carried).

Next steps

Book a free trial with an IGCSE Biology tutor to practise hormone and plant response questions, or explore Tutopiya’s learning portal for more revision resources.