2.1.1 Principles of Organisation

Animal Cell

Plant Cell

• Tissues are groups of specialised cells that have a similar structure and work together to perform a specific function. Tissues can consist of one or more types of cells. For example:
  • Muscular tissue: Composed of muscle cells, it is responsible for movement.
  • Epithelial tissue: Made up of epithelial cells, it covers and protects surfaces both inside and outside the body, such as the lining of the stomach or the skin.

Muscular tissue

Epithelial tissue

• Organs are structures made up of different types of tissues working together to carry out a particular function. Each tissue within an organ contributes to the organ's overall role. For instance:
  • The stomach is an organ that plays a critical role in digestion. It contains:
  • Muscular tissue: Helps churn and mix food.
  • Epithelial tissue: Protects the stomach lining and secretes digestive enzymes.

• Organ systems are groups of organs that work together to perform complex functions necessary for the body's survival. Each organ within the system has a specific role that contributes to the system's overall function. For example:
  • The digestive system includes the stomach, liver, small intestine, and other organs that work together to break down food, absorb nutrients, and eliminate waste.