Cell organisation

Large Multicellular organisms are made up of Organ Systems

Specialised cells carry out a particular function

The process of becoming specialised is known as Differentiation

Differentiation occurs during the development of multicelluar organisms

These specialised cells form tissues, which form organs, which form Organ Systems

Large multi cellular organisms have different systems inside them for exchanging and transporting materials

Similar cells are organised into Tissues

A tissue is a group of similar cells that work together to carry out a particular function. It can include more than one type of cell. Examples of tissues can include:

• Muscular tissue: contracts and shortens to move to whatever it's attached to
• Glandular tissue: Makes and secretes chemicals like enzymes and hormones
• Epithelial tissue: Covers the outside and inside of the stomach

An organ is a group of different tissues that work together to perform a certain function. For example, to stomach is an organ made of these tissues:

• Muscular tissue: Moves the stomach wall to churn up food
• Glandular tissue: Makes digestive juices to digest food
• Epithelial tissue: Covers the outside and inside of the stomach

An organ system is a group of organs working together to perform a particular function. For example: 

The digestive system

1) Glands: produce digestive juices

2) The stomach and small intestine digest food

3) The liver produces bile

4) The small intestine absorbs soluble food molecules

5) The large intestine absorbs water from undigested food to produce faeces