Animals exhibit different patterns of organisation: Cellular level of organisation :
- Cells are loosely arranged without the formation of tissues.
- There is division of labour among the cells, e.g., sponges.
Tissue level of organisation :
- Cells which perform similar function are grouped into tissues.
- The tissues perform a common function, e.g., cnidarians.
Organ level of organisation : Different kinds of tissues aggregate to form an organ to perform a specific function e.g., flatworms and other hyper phyla.
Organ system level of organisation :
- The tissues are organised to form organs and organ systems.
- All the organ system function in a coordinated manner.