Levels of Organisation (Edexcel IGCSE Biology: Double Science)

• Cells are the basic building blocks of all living organisms
• Unicellular organisms are made from one cell, whereas multicellular organisms are made up of collections of cells
• Cells are made up of structures called organelles, such as the nucleus, mitochondria and ribosomes
• In complex multicellular organisms:
  • Cells are specialised to carry out particular functions
  • These specialised cells form tissues
  • The tissues form organs
  • The organs form organ systems

Different Levels of Organisation Table

Multicellular organisms have many levels of organisation

Examples of Organ Systems in Animals & Plants Table