Principles of Organisation¶
Part of 4.2 Organisation.
Organisation shows how biology scales up from individual cells to whole organisms. The key idea is hierarchy: cells form tissues, tissues form organs, and organs work together in organ systems.
Learning Objectives¶
| ID | Official specification wording | Main teaching sections |
|---|---|---|
4.2.1-lo-1 |
4.2.1 Cells are the basic building blocks of all living organisms. 4.2.1 A tissue is a group of cells with a similar structure and function. 4.2.1 Organs are aggregations of tissues performing specific functions. 4.2.1 Organs are organised into organ systems, which work together to form organisms. |
Cells, Tissues, Organs and Organ Systems |
Cells, Tissues, Organs and Organ Systems¶
- Cells are the basic building blocks of living organisms.
- A tissue is a group of cells with a similar structure and function.
- An organ is made from different tissues working together to perform a specific function.
- Organ systems coordinate multiple organs so the whole organism can survive. The digestive system is a useful example because organs such as the stomach, intestines, liver and pancreas work together to digest food and absorb useful molecules.
- Thinking in this hierarchy helps you explain how microscopic structures contribute to whole-body functions.
Common Confusions¶
- Tissue vs organ: a tissue is a group of similar cells doing one job; an organ contains different tissues working together.
- Organ vs organ system: an organ performs one specific function, while an organ system is a group of organs working together.
Key Terms¶
- Cell: the basic building block of a living organism.
- Tissue: a group of specialised cells working together to perform a function.
- Organ: a structure made from different tissues working together.
- Organ system: a group of organs that work together to carry out a major function.