Biology · Cell Types
Levels of Organisation
1. From cell to organism
Living things are organised in levels: cell → tissue → organ → organ system → organism. Each level is built from the one before it and adds new functions.
2. The Four Main Animal Tissue Types
The four main animal tissue types are epithelial, connective, muscle and nervous tissue. Each main type contains several varieties, but detailed varieties are outside this lesson.
3. Structure Fits Function
| Epithelial | Covers surfaces and lines cavities |
| Connective | Supports and binds other tissues |
| Muscle | Contracts to produce movement |
| Nervous | Carries electrical signals |
