Organisation is a core part of GCSE Biology. Revise the key concepts and common mistakes below, then lock them in with the free games.
Key concepts
CellThe basic unit of life.
TissueSimilar cells working together.
OrganTissues forming a functional unit.
Organ systemOrgans working together.
DifferentiationCells becoming specialised.
Levels of organisationCells → tissues → organs → systems.
StimulusDetectable change in environment
ReceptorCell or organ that detects a stimulus
EffectorMuscle or gland producing the response
SynapseGap between neurones bridged by chemicals
HormoneChemical messenger carried in blood
HomeostasisKeeping internal conditions constant
CerebrumLargest brain area — conscious thought
CerebellumCoordinates muscles and balance
Common mistakes to avoid
Questions where students often pick the tempting wrong answer — make sure you know the right one:
What drives water up the xylem in a tall tree?✗ Roots actively pump water up to the leaves like a heart. ✓ Transpiration pull — evaporation from leaves creates tension that pulls water up the continuous water column.
In osmosis, which direction does water move?✗ Water moves from high solute concentration to low solute concentration. ✓ From a region of higher water potential (less concentrated solution) to lower water potential.
How do hormones reach their target organs?✗ Hormones are sent through nerves directly to specific organs. ✓ They are carried in the bloodstream and act on cells with specific receptors for that hormone.
What is the correct order of organisation?✗ Tissues → cells → organs → systems. ✓ Cells → tissues → organs → organ systems.
Can a single cell be a complete living organism?✗ No, life always needs many cells. ✓ Yes — many organisms (e.g. amoeba, bacteria) are single-celled.
Practise Organisation — free games
Test yourself with these quick revision games for this topic:
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