Revision notes · Organisation
Principles of organisation
Principles of organisation4.2.1
Definition: The levels of organisation in a multicellular organism run from cells, up through tissues and organs, to organ systems and the whole organism.
Multicellular organisms are built from a hierarchy of increasingly complex structures.
| Level | Example |
|---|---|
| Cell | Muscle cell |
| Tissue | Muscular tissue |
| Organ | Stomach |
| Organ system | Digestive system |
| Organism | Human |
- •A tissue is a group of similar cells that work together to perform a shared function.
- •An organ is made of several different tissues working together.
- •An organ system is a group of organs working together to perform an overall function.
⚠️ Common mistake: Thinking an organ is made of only one type of tissue — an organ is always built from several different tissues working together.
🧠 Remember: Smallest to largest: Cells → Tissues → Organs → Organ systems → Organism.
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