Levels of Organisation (Edexcel IGCSE Biology)

Cells, Tissues, Organs & Organ Systems

• 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